Genset overprovisioning...

[Dean Hoffman]

On Sunday, April 23, 2023 at 3:05:07 PM UTC-5, Don Y wrote:

On 4/23/2023 9:54 AM, Dean Hoffman wrote:
No. The load on the power unit was just the generator supplying
electricity to the center pivot. That was small but varied.
So, wrt the ~65hp, how much of a load was the generator? I.e., was the
engine as oversized for *that* load as the example I\'m giving?

The load with the center pivot running dry at maximum speed would never be
over 7 hp.even on the older systems. It would probably drop to around 4 hp.
at times. The towers start and stop to keep in line with the next one to
the outside of the circle. Tower 1 runs 1/7th as much as tower 7 on a
regular pivot.
Ah! So more like 3-5KW out of ~50KW (engine) capacity. That might be
comparable to the range of loads I\'m looking at (scaled by a factor).

[Does the diesel just have a fixed governor that you tweek for the desired
generator RPM? How sensitive *your* (his) loads to frequency variation?]

A Lima generator for pivots is supposed to put out 480 volts, 60 hz.
<https://www.regalrexnord.com/brands/Marathon-Generators/Products/lima-mac>
The drive motors for the individual towers are probably the only things affected at all.
That\'s really unnoticeable with all the other things that could matter. Center pivots have
480x 120 volt transformers to provide voltage for the contactors and relays that control things.
Frequency wouldn\'t change more than about 8% either up or down.
Incidentally, newer center pivots have 1/2 hp. drive motors on the towers. The maximum
load couldn\'t be over 3 1/2 hp. when they\'re running dry.

The diesel engines have throttles that one sets to desired speed. The
governors on the injection pumps keep the speed fairly constant after that.
Pivots would run ok from about 440 vac to maybe 510 vac or so. They aren\'t
all that finicky. Modern electronics on pivots have voltage monitors to
shut them off if voltage drops too much. Now a farmer can sit at his
breakfast table to check his systems. They go check the ones that have
stopped unexpectedly to see what happened.
But are they frequency insensitive? I\'d be concerned that a
change in engine speed would result in frequency disturbances.
Not sure how well \"home appliances\" would deal with that.
Downside is you\'re dependant on the natural gas supply. We\'ve had one
occasion where the supply to the town wasn\'t sufficient to heat all the
homes (high demand in an unusually cold spell) and most furnaces would
simply refuse to run due to insufficient heat from the available fuel.

I read recently about some people not having gas heat because some of the
natural gas company\'s pumps would\'t work due to no electrical supply.
Dunno. But, *gasoline* (and diesel) pumps would likely be \"out\" if a
widespread power outage. So, not a reliable fuel source

In our (natural gas) outage, there was gas. Just not at a high
enough distribution pressure to satisfy the safeties in the
appliances that used it. I\'d watch the furnace call for gas,
watch the igniter kick in, flame appear... then, the gas valve
shut down as the safeties didn\'t sense \"enough heat\" to convince
themselves that the fire was lit. Evacuate the fumes. Wait.
Repeat.

Plumbers had a field day from all the idiots who just thought
their furnace was \"broken\". Gotta wonder how the plumbers
could NOT just tell the callers \"check for flame; if none,
we\'ll come out. Otherwise, it\'s caused by a regional supply
outage\".

But, hey, why NOT screw over your (ignorant) customers? :

 

[Don Y]

On 4/23/2023 1:14 PM, boB wrote:

On Sat, 22 Apr 2023 16:09:30 -0700, Don Y
blockedofcourse@foo.invalid> wrote:

On 4/22/2023 1:24 PM, boB wrote:
On Fri, 21 Apr 2023 20:30:57 -0700, Don Y
blockedofcourse@foo.invalid> wrote:

I\'m looking at a *big* genset (100KW++) -- great price.

But, my needs are nowhere near that (I think the house
has a ~25KW feed -- and we likely never approach that!)

However, I\'m wondering if the (relatively) small load
would make the genset\'s \"control\" tougher to keep
on mark?

What kind of generator is it ?

I\'m not sure I understand what you\'re after...
make/model? fuel source? somethingelse?


Generac ? Onan ? Etc ?

There are a variety of different makes/models.

Onan seems to be primarily geared towards smaller units
that *appear* to be pulls from RVs? (they tend to emphasize
\"quiet\").

Mitsubishi, generac, hannay, etc. seem to make t he
larger (non-military) units. Above the 25-35KW capacity,
they seem to be more for industrial use. Some trailer
mounted, etc.

There are also specialty units \"packaged\" for specific
applications (e.g., remote jobsite lighting where the genset
and light tower are packaged on a trailer). Not sure
how this may effect their design (given that lights
tend not to be too fussy as loads).

I\'ve not looked into specific models as I am more concerned
with the oversizing aspect, presently. (would you buy a
\"lorry\" if you really only needed a pickup?)

 

[Don Y]

On 4/23/2023 2:34 PM, Dean Hoffman wrote:

On Sunday, April 23, 2023 at 3:05:07 PM UTC-5, Don Y wrote:
On 4/23/2023 9:54 AM, Dean Hoffman wrote:
No. The load on the power unit was just the generator supplying
electricity to the center pivot. That was small but varied.
So, wrt the ~65hp, how much of a load was the generator? I.e., was
the engine as oversized for *that* load as the example I\'m giving?

The load with the center pivot running dry at maximum speed would never
be over 7 hp.even on the older systems. It would probably drop to around
4 hp. at times. The towers start and stop to keep in line with the next
one to the outside of the circle. Tower 1 runs 1/7th as much as tower 7
on a regular pivot.
Ah! So more like 3-5KW out of ~50KW (engine) capacity. That might be
comparable to the range of loads I\'m looking at (scaled by a factor).

[Does the diesel just have a fixed governor that you tweek for the
desired generator RPM? How sensitive *your* (his) loads to frequency
variation?]

A Lima generator for pivots is supposed to put out 480 volts, 60 hz.
https://www.regalrexnord.com/brands/Marathon-Generators/Products/lima-mac
The drive motors for the individual towers are probably the only things
affected at all. That\'s really unnoticeable with all the other things that
could matter.

I would assume that -- as long as they *track* -- any frequency variation
would just make the whole rig rotate slightly faster/slower. The problem
would be if they drifted too far out of range that the motors couldn\'t
develop enough torque, etc.

[But, that would likely be very visible]

Center pivots have 480x 120 volt transformers to provide
voltage for the contactors and relays that control things. Frequency
wouldn\'t change more than about 8% either up or down. Incidentally, newer
center pivots have 1/2 hp. drive motors on the towers. The maximum load
couldn\'t be over 3 1/2 hp. when they\'re running dry.

I don\'t know how household appliances would react to variations
from \"nominal mains voltage/frequency\". Consider they are likely
designed with slim margins (to save a few pennies).

Electronic devices probably wouldn\'t mind as their input (DC) filters
would probably bridge even (marginally) lengthened cycles. I have
a few devices that would complain because they expect the mains to
be \"well behaved\" (in frequency and voltage). But, they would be able
to *report* those problems (and I can\'t think of any where I would
have intentionally crippled the design if those constraints were
violated... they\'d just make \"best efforts\" in the face of the
deviations).

[I wonder if my UPSs would complain? They tend to want to be able
to detect \"line abnormalities\" sooner rather than later. So, may
be relatively intolerant of modest deviations.]

Furnace (blower) would likely just change the airflow rate but
I can\'t imagine it would be enough to cause the heat exchanger
to fail due to insufficient flow. I think the washer and
refrigerator have VFDs so they should behave (not sure how other
folks\' would perform without that intermediary drive).

Evaporative cooler would be even more tolerant than the furnace
(no temperature extremes resulting from altered operating point.
Stove/oven\'s big loads are resistive.

Freezer is a dumb compressor so I wouldn\'t know how far out of
range it could adapt. Ditto with ACbrrr compressor. I assume the
garage door opener wouldn\'t be pushed too far outside of its
SoA with such variations (esp as a properly installed door is
supposed to pose a small load on the opener).

And, not sure how any of the electronic devices that also
track the passing of time would fare. Hard to imagine they rely
on XTALs for that information so they might see \"time drift\"
if mains frequency varied. Hopefully, they are smart
enough to know to drop frequency lock if the deviation is
too great (that\'s what my devices do).

 

[Don Y]

On 4/23/2023 8:14 PM, Don Y wrote:

And, not sure how any of the electronic devices that also
track the passing of time would fare.  Hard to imagine they rely
on XTALs for that information so they might see \"time drift\"
if mains frequency varied.  Hopefully, they are smart
enough to know to drop frequency lock if the deviation is
too great (that\'s what my devices do).

I tried to tabulate the \"base loads\" here (assuming we make no
lifestyle changes in the absence of mains utility power).

The \"low\" number is likely ~100W just for \"idle controls\"
(assuming the devices in question are \"off\" and idling
consumes < 1W).

Most devices no longer have galvanic power switches.
So, there\'s always \"something\" watching to see if you
want to turn the device on.

Some are this way of necessity (e.g., your traditional garage
door opener never knows when you might call on it to actuate
for entry or egress). And, most HVAC-related controls are
similarly naive: they sit and watch temperatures continuously
instead of checking when it makes more sense to do so
(e.g., if the furnace just shut off, it\'s not likely that
the house is going to call for more heat in the next ten
minutes so why are you waiting for that demand?)

Many appliances would know that they won\'t be called upon
if, for example, the occupants were away from home (or
asleep). Yet, they sit there waiting for an Ir signal
or a keypad touch... \"just in case\".

I\'m piggish with my PCs/servers... letting them \"sleep\"
when not in use in the belief that they draw roughly the
same power as if \"off\" waiting for a \"soft-power on\".
Ditto monitors. I suspect mice and keyboards use just
as much power when \"off\" as \"on\"!

I *do* pull the power cords on the few servers that insist on
running fans while \"off\". If you need to run a fan, then
you\'re probably drawing more power than necessary while \"off\".
(And, I dislike unnecessary fan noise -- even low speed)

And, all of the shelfs in my SANs have real power switches
so I use them instead of relying on \"soft-power\" controls.

But, it seems like damn near everything that is connected
to power, nowadays, has some vampire/quiescent/standby power!
(even *fans*!) \"Convenience\". :>

 

[Joerg]

On 4/21/23 8:30 PM, Don Y wrote:

I\'m looking at a *big* genset (100KW++) -- great price.

But, my needs are nowhere near that (I think the house
has a ~25KW feed -- and we likely never approach that!)

However, I\'m wondering if the (relatively) small load
would make the genset\'s \"control\" tougher to keep
on mark?

I don\'t think so but its efficiency at small loads will be horrible.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Tabby]

On Monday, 24 April 2023 at 04:14:34 UTC+1, Don Y wrote:

On 4/23/2023 2:34 PM, Dean Hoffman wrote:
On Sunday, April 23, 2023 at 3:05:07 PM UTC-5, Don Y wrote:
On 4/23/2023 9:54 AM, Dean Hoffman wrote:

[Does the diesel just have a fixed governor that you tweek for the
desired generator RPM? How sensitive *your* (his) loads to frequency
variation?]

A Lima generator for pivots is supposed to put out 480 volts, 60 hz.
https://www.regalrexnord.com/brands/Marathon-Generators/Products/lima-mac
The drive motors for the individual towers are probably the only things
affected at all. That\'s really unnoticeable with all the other things that
could matter.
I would assume that -- as long as they *track* -- any frequency variation
would just make the whole rig rotate slightly faster/slower. The problem
would be if they drifted too far out of range that the motors couldn\'t
develop enough torque, etc.

[But, that would likely be very visible]
Center pivots have 480x 120 volt transformers to provide
voltage for the contactors and relays that control things. Frequency
wouldn\'t change more than about 8% either up or down. Incidentally, newer
center pivots have 1/2 hp. drive motors on the towers. The maximum load
couldn\'t be over 3 1/2 hp. when they\'re running dry.
I don\'t know how household appliances would react to variations
from \"nominal mains voltage/frequency\". Consider they are likely
designed with slim margins (to save a few pennies).

Most don\'t worry about 8%. Record decks & electric clocks just misbehave harmlessly.
A bigger issue is inductive spikes, electronics on small gens are a scenario where surge absorbers are useful.

Freezer is a dumb compressor so I wouldn\'t know how far out of
range it could adapt.

They don\'t much care. If it\'s a long way off it will stall/trip more, but that doesn\'t normally stop them doing the job.

 

[bob prohaska]

Joerg <news@analogconsultants.com> wrote:

On 4/21/23 8:30 PM, Don Y wrote:
I\'m looking at a *big* genset (100KW++) -- great price.

But, my needs are nowhere near that (I think the house
has a ~25KW feed -- and we likely never approach that!)

However, I\'m wondering if the (relatively) small load
would make the genset\'s \"control\" tougher to keep
on mark?


I don\'t think so but its efficiency at small loads will be horrible.

Aye, there\'s the rub

It appears to me that no-load fuel consumption is around .1 gph per kW
of load plus rating for smallish gasoline units. Diesels would be better,
inverters can be better, maybe bigger is better, but a 4x oversize will bite
pretty hard. To be useful, you have to have fuel on-hand all the time. If
you only need a day\'s endurance, oversizing isn\'t so costly. If you need a
week, it\'s going to be a big tank.

A free generator is the easy third of the problem: You need fuel and
distribution to complete the tripod. If you already have fuel on hand,
then the oversized generator might be a very good deal. If not, the fuel
storage is the hard part.

I started with a cheap (5kW) generator and gradually realized that UPS units
with overnight endurance for critical loads is a better way to start out.
As it happens, I do have fuel (33gal tank in my car), enough for a few days.
That wasn\'t planning, just dumb luck.

hth,

bob prohaska

 

[Don Y]

On 4/26/2023 7:42 PM, bob prohaska wrote:

Joerg <news@analogconsultants.com> wrote:
On 4/21/23 8:30 PM, Don Y wrote:
I\'m looking at a *big* genset (100KW++) -- great price.

But, my needs are nowhere near that (I think the house
has a ~25KW feed -- and we likely never approach that!)

However, I\'m wondering if the (relatively) small load
would make the genset\'s \"control\" tougher to keep
on mark?


I don\'t think so but its efficiency at small loads will be horrible.

Aye, there\'s the rub

It appears to me that no-load fuel consumption is around .1 gph per kW
of load plus rating for smallish gasoline units. Diesels would be better,
inverters can be better, maybe bigger is better, but a 4x oversize will bite
pretty hard. To be useful, you have to have fuel on-hand all the time. If
you only need a day\'s endurance, oversizing isn\'t so costly. If you need a
week, it\'s going to be a big tank.

There are several ways of looking at that aspect.

For a day, one could likely live without air conditioning (or heat), could
keep the refrigerator/freezer buttoned up tight (no unnecessary \"browsing\"),
rely on a laptop instead of a workstation, eat canned goods (heat over an
outdoor fire improvised from on-hand fuel stores) opened with a MANUAL
canopener, etc.

For a *week* (disaster?), the toll of living without quickly grows. A
refrigerator/freezer isn\'t going to hold up for extended periods of time
so, plan on doing a LOT of cooking (to salvage stored foods). That puts
a bigger load on some other \"fuel consumer\" -- an outdoor grill, a gas
appliance, etc.

Soon, we won\'t be able to live comfortably without air conditioning (summer
starts in April; we\'ve already hit 100F). This will persist through September
(to varying degrees... worsening during Monsoon as a consequence of the higher
humidity). Even nighttime lows will bottom out in the 80\'s.

[Winter is easier to tolerate power loss as the daytime temperatures
are still 70+ and even cold nights -- 30F -- could be tolerated with
extra layers of clothing]

For a prolonged outage, you have to wonder if your source of
additional fuel will continue to be available. It\'s unlikely
that just your home/neighborhood is suffering, in that case.
Will the local gas station (gasoline/diesel) be able to run
their pumps? Will scheduled deliveries (tankers) continue
uninterrupted? How long will you queue for fuel that is in
shorter supply?

Relying on a vehicle\'s fuel storage ability means you will
be juggling the fuel available in the vehicle as a supply for
the genset vs. as a possible means of departing the area
(or, conducting extended foraging runs if store shelves start
to go bare) if the need arises.

[I wonder what its like in places that get decimated by hurricanes?]

A free generator is the easy third of the problem: You need fuel and
distribution to complete the tripod. If you already have fuel on hand,
then the oversized generator might be a very good deal. If not, the fuel
storage is the hard part.

I actually think the more immediate concerns are (re)deploying a
genset that isn\'t an integral part of your homestead and lifestyle.
Gensets are fine if you are *camping* or living off grid. But, if
they are an *exceptional* source of power, there are often lots
of hassles associated with their use. (would it be easier to just
check in to a hotel for the duration of the outage?)

A portable unit needs to be hauled out to a place where it can
be safely operated without danger of toxic fumes, interference
by neighbors/wildlife (you wouldn\'t want a curious neighborhood
child to be injured \"exploring\" it), protection from the elements,
accessibility (so you can check on it as well as service/refuel it),
etc.

Then, the unit needs to be tethered to the loads. If you\'ve opted
for portable, you\'ve likely not opted to install a bypass. So, run
a (long) cord(s) to the load(s) of interest. Careful not to trip!
(or, accidentally dislodge one!)

[You wouldn\'t want to back-feed the house from a single point without
a disconnect as the risk of mistake is too high. And, the task of
manually connecting -- and isolating the utility -- means \"special\"
skills are needed (not something your other half is likely going to
be keen on doing -- just as they\'d not be keen on wheeling the
genset out to a convenient operating point and running cords)]

And, if you\'ve sized the genset (portable or otherwise) for anything
less than your whole house load, you now have to actively manage
your loads; amusingly, the loads that you\'d typically want to backup
(freezer, refrigerator, HVAC) already have \"automatic controls\"
because managing their use manually would be tediously impractical.
So, you\'d have to remember to turn each of these OFF (assuming they
are then tethered to the genset) and manually divide the available
power amongst them.

[Again, not something that you\'ll want to be doing constantly -- and
likely not a chore that is easily RELIABLY delegated]

Then, someone has to start it (even if electric start) and attend to
it\'s fuel needs. Assuming it has been properly maintained in the
\"off season\".

[You always discover dead batteries in your flashlight when you
NEED the flashlight! :> ]

There\'s an appeal to a TURNKEY whole-house genset plumbed to the
natural gas supply -- assuming THAT is not interrupted! But, that
comes with a high price tag if you also don\'t want to have to
deal with load management, etc.

[\"Quick, everyone... turn off all nonessential loads so the genset
won\'t struggle to come on-line!\"]

I started with a cheap (5kW) generator and gradually realized that UPS units
with overnight endurance for critical loads is a better way to start out.
As it happens, I do have fuel (33gal tank in my car), enough for a few days.
That wasn\'t planning, just dumb luck.

That was our initial strategy; gasoline powered so the gas fueled cars
could act as fuel storage containers that are capable of transporting
themselves to a \"filling station\". You\'d not want to have to lug a
bunch of 5G cans of fuel back and forth!

But, you quickly have to discard many loads for small gensets. Most
loads are really large loads that AVERAGE OUT to smaller loads. But,
a genset would \"see\" the large peak load.

E.g., the 1000W microwave oven is either drawing 1000W or (essentially)
0W. The output power (to the load being heated) is the average of
these. Likewise, an electric stovetop/oven cycles between a few KW
and nothing to maintain a desired temperature setting. Air conditioning,
heating, hot water, refrigeration, etc. are each \"all or nothing\" loads.

So, even if you actively stagger each such load, you still have to
size the genset for the largest of these that you want to use, even
if it is on for a very short duty cycle! E.g., we\'d have to buy a
\"room air conditioner\" to tolerate outages of any length if we couldn\'t
supply the ~12+KW that the ACbrrr requires (neglecting startup current).
That means finding a room that can be isolated from the rest of the
heating/cooling space so the unit could be effective (we have an open
floor plan so we\'d have to choose *a* bedroom as a \"sanctuary\"). And,
storing that device when it isn\'t needed. And, planning on redeploying
it during an outage (running power to it and venting the \"exhaust\" heat
out a nearby window).

If you look at EVERYTHING that is involved, fuel is just *one* of
those annoying little details.

Finally, there\'s no guarantee that you will EVER need this capability!
Or, that when a need arises, you will be able to predict how long the
need will persist to come to an appropriate decision as to whether or
not you want to begin the task of switching to your \"alternate plans\".

I have ~20 UPSs, here. There\'s a 500VA unit that keeps my name/time/font/etc.
server running. Another for SWMBOs computer. A 750VA unit on each of my
6 workstations. A pair of 1.5KVA units to power my monitors. Another pair
of 1.5KVA units to power the SANs. A 1.5KVA for *this* computer and the
internet link. Another for the TV/DVR/DVD. A pair of 2.2KVA units for my
automation system. And a 5KVA unit that will ultimately replace the 2.2KVA
units in their role.

*BATTERIES* become the problem (just like \"fuel\" for the genset).
The batteries for the 5KVA weigh ~400 pounds!

Plus, unlike gasoline/diesel/propane/natural gas, when the batteries run flat,
there\'s no easy way to recharge them in the absence of power!

And, it\'s the same sort of \"manual\" system described for the genset; to use
them (for anything other than their *nominal* applications), you have
to start stringing power cords around the house as their normal loads
aren\'t where you will want to use power when power is scarce!

Much easier in a camping/off-grid situation where the cost and permanence
of the setup is more readily apparent.

 

[bob prohaska]

Don Y <blockedofcourse@foo.invalid> wrote:

On 4/26/2023 7:42 PM, bob prohaska wrote:
Joerg <news@analogconsultants.com> wrote:
On 4/21/23 8:30 PM, Don Y wrote:
I\'m looking at a *big* genset (100KW++) -- great price.

But, my needs are nowhere near that (I think the house
has a ~25KW feed -- and we likely never approach that!)

However, I\'m wondering if the (relatively) small load
would make the genset\'s \"control\" tougher to keep
on mark?


I don\'t think so but its efficiency at small loads will be horrible.

Aye, there\'s the rub

It appears to me that no-load fuel consumption is around .1 gph per kW
of load plus rating for smallish gasoline units. Diesels would be better,
inverters can be better, maybe bigger is better, but a 4x oversize will
bite pretty hard. To be useful, you have to have fuel on-hand all the time.
If you only need a day\'s endurance, oversizing isn\'t so costly. If you
need a week, it\'s going to be a big tank.

There are several ways of looking at that aspect.

Clearly you\'ve overthought the problem as badly as I have
FWIW, my own ruminations are at
http://www.zefox.net/~bob/backup_power/

One paper on fuel selection for generators is at
https://www.nrel.gov/docs/fy19osti/72509.pdf

For a day, one could likely live without air conditioning (or heat), could
keep the refrigerator/freezer buttoned up tight (no unnecessary \"browsing\"),
rely on a laptop instead of a workstation, eat canned goods (heat over an
outdoor fire improvised from on-hand fuel stores) opened with a MANUAL
canopener, etc.

The outage duration has huge impact on behavior. When duration is unknown
all decisions (to open the fridge or not) become un-answerable and so a source
of stress. A backup system serves mostly to limit that stress, whether it\'s
called into service or not.

For a *week* (disaster?), the toll of living without quickly grows. A
refrigerator/freezer isn\'t going to hold up for extended periods of time
so, plan on doing a LOT of cooking (to salvage stored foods). That puts
a bigger load on some other \"fuel consumer\" -- an outdoor grill, a gas
appliance, etc.

I\'d put food storage near the top of the backup priority list.

Soon, we won\'t be able to live comfortably without air conditioning (summer
starts in April; we\'ve already hit 100F). This will persist through September
(to varying degrees... worsening during Monsoon as a consequence of the higher
humidity). Even nighttime lows will bottom out in the 80\'s.

AC is an expensive problem. I\'d aim the for smallest genny that can start it.

For a prolonged outage, you have to wonder if your source of
additional fuel will continue to be available. It\'s unlikely
that just your home/neighborhood is suffering, in that case.
Will the local gas station (gasoline/diesel) be able to run
their pumps? Will scheduled deliveries (tankers) continue
uninterrupted? How long will you queue for fuel that is in
shorter supply?

It\'s easy to imagine intractable scenarios. Look at the history
to see what\'s plausible. For me, that\'s a few days.

Relying on a vehicle\'s fuel storage ability means you will
be juggling the fuel available in the vehicle as a supply for
the genset vs. as a possible means of departing the area
(or, conducting extended foraging runs if store shelves start
to go bare) if the need arises.


[I wonder what its like in places that get decimated by hurricanes?]

Either a lot of stored fuel or carefully-chosen compromises in lifestyle
for the duration.

A free generator is the easy third of the problem: You need fuel and
distribution to complete the tripod. If you already have fuel on hand,
then the oversized generator might be a very good deal. If not, the fuel
storage is the hard part.

I actually think the more immediate concerns are (re)deploying a
genset that isn\'t an integral part of your homestead and lifestyle.
Gensets are fine if you are *camping* or living off grid. But, if
they are an *exceptional* source of power, there are often lots
of hassles associated with their use. (would it be easier to just
check in to a hotel for the duration of the outage?)

In the outage, yes absolutely. Planning is the stage to control the hassles.

A portable unit needs to be hauled out to a place where it can
be safely operated without danger of toxic fumes, interference
by neighbors/wildlife (you wouldn\'t want a curious neighborhood
child to be injured \"exploring\" it), protection from the elements,
accessibility (so you can check on it as well as service/refuel it),
etc.

Then, the unit needs to be tethered to the loads. If you\'ve opted
for portable, you\'ve likely not opted to install a bypass. So, run
a (long) cord(s) to the load(s) of interest. Careful not to trip!
(or, accidentally dislodge one!)

[You wouldn\'t want to back-feed the house from a single point without
a disconnect as the risk of mistake is too high. And, the task of
manually connecting -- and isolating the utility -- means \"special\"
skills are needed (not something your other half is likely going to
be keen on doing -- just as they\'d not be keen on wheeling the
genset out to a convenient operating point and running cords)]

A portable generator interlock and inlet receptable needn\'t be much
work. Being manual it\'s relatively cheap and mostly exempt from NEC
regulation. Automatic systems are a very different story.

And, if you\'ve sized the genset (portable or otherwise) for anything
less than your whole house load, you now have to actively manage
your loads; amusingly, the loads that you\'d typically want to backup
(freezer, refrigerator, HVAC) already have \"automatic controls\"
because managing their use manually would be tediously impractical.
So, you\'d have to remember to turn each of these OFF (assuming they
are then tethered to the genset) and manually divide the available
power amongst them.

[Again, not something that you\'ll want to be doing constantly -- and
likely not a chore that is easily RELIABLY delegated]

Then, someone has to start it (even if electric start) and attend to
it\'s fuel needs. Assuming it has been properly maintained in the
\"off season\".

[You always discover dead batteries in your flashlight when you
NEED the flashlight! :> ]

There\'s an appeal to a TURNKEY whole-house genset plumbed to the
natural gas supply -- assuming THAT is not interrupted! But, that
comes with a high price tag if you also don\'t want to have to
deal with load management, etc.

[\"Quick, everyone... turn off all nonessential loads so the genset
won\'t struggle to come on-line!\"]

All of which argues in favor of a grid-backed battery/solar/islanding-
inverter system with a generator as a cherry on top Great if you
have both need and sufficient money.

I started with a cheap (5kW) generator and gradually realized that UPS units
with overnight endurance for critical loads is a better way to start out.
As it happens, I do have fuel (33gal tank in my car), enough for a few days.
That wasn\'t planning, just dumb luck.

That was our initial strategy; gasoline powered so the gas fueled cars
could act as fuel storage containers that are capable of transporting
themselves to a \"filling station\". You\'d not want to have to lug a
bunch of 5G cans of fuel back and forth!

But, you quickly have to discard many loads for small gensets. Most
loads are really large loads that AVERAGE OUT to smaller loads. But,
a genset would \"see\" the large peak load.

E.g., the 1000W microwave oven is either drawing 1000W or (essentially)
0W. The output power (to the load being heated) is the average of
these. Likewise, an electric stovetop/oven cycles between a few KW
and nothing to maintain a desired temperature setting. Air conditioning,
heating, hot water, refrigeration, etc. are each \"all or nothing\" loads.

AC is much worse, the genny has to be sized to starting loads. Stoves
are resistive and much easier. Electric water heat, unless heat-pump,
strikes me as folly in the present day.

Load management appears unavoidable to me.

So, even if you actively stagger each such load, you still have to
size the genset for the largest of these that you want to use, even
if it is on for a very short duty cycle! E.g., we\'d have to buy a
\"room air conditioner\" to tolerate outages of any length if we couldn\'t
supply the ~12+KW that the ACbrrr requires (neglecting startup current).
That means finding a room that can be isolated from the rest of the
heating/cooling space so the unit could be effective (we have an open
floor plan so we\'d have to choose *a* bedroom as a \"sanctuary\"). And,
storing that device when it isn\'t needed. And, planning on redeploying
it during an outage (running power to it and venting the \"exhaust\" heat
out a nearby window).

Mini split heat pump?

If you look at EVERYTHING that is involved, fuel is just *one* of
those annoying little details.

And, the cost of the generator is the least of the weevils

Finally, there\'s no guarantee that you will EVER need this capability!
Or, that when a need arises, you will be able to predict how long the
need will persist to come to an appropriate decision as to whether or
not you want to begin the task of switching to your \"alternate plans\".

The only sure benefit of a power backup system is peace of mind.

I have ~20 UPSs, here. There\'s a 500VA unit that keeps my name/time/font/etc.
server running. Another for SWMBOs computer. A 750VA unit on each of my
6 workstations. A pair of 1.5KVA units to power my monitors. Another pair
of 1.5KVA units to power the SANs. A 1.5KVA for *this* computer and the
internet link. Another for the TV/DVR/DVD. A pair of 2.2KVA units for my
automation system. And a 5KVA unit that will ultimately replace the 2.2KVA
units in their role.

Endurance is the key for UPS units. Most computer units are intended to
allow only a graceful shutdown. I suggest enough battery capacity to let
you ignore outages overnight, at least.

*BATTERIES* become the problem (just like \"fuel\" for the genset).
The batteries for the 5KVA weigh ~400 pounds!

Lithium iron phosphate is lighter, longer lasting and faster charging.
Purchase cost is higher, lifetime cost seems comparable to lead-acid.
Backup power is like insurance, it always costs extra.

Plus, unlike gasoline/diesel/propane/natural gas, when the batteries run flat,
there\'s no easy way to recharge them in the absence of power!

Desperate times call for desperate measure.....

And, it\'s the same sort of \"manual\" system described for the genset; to use
them (for anything other than their *nominal* applications), you have
to start stringing power cords around the house as their normal loads
aren\'t where you will want to use power when power is scarce!

Individual extension cords are a bad option. A single cord from genny to inlet
receptacle is easier and cheaper than point-of-use cords. A generator interlock
on a main panel can be a DIY project in some jurisdictions, ~1-200$

Much easier in a camping/off-grid situation where the cost and permanence
of the setup is more readily apparent.

Agreed, but in the end the most realistic setup is likely to be very similar
to a yacht or RV: Closely-sized genset for big intermittent loads, closely
sized inverters and (abundant) batteries for small continuous loads.

Thanks for reading if you got this far!

bob prohaska

 

[John Larkin]

On Wed, 26 Apr 2023 22:26:37 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:

On 4/26/2023 7:42 PM, bob prohaska wrote:
Joerg <news@analogconsultants.com> wrote:
On 4/21/23 8:30 PM, Don Y wrote:
I\'m looking at a *big* genset (100KW++) -- great price.

But, my needs are nowhere near that (I think the house
has a ~25KW feed -- and we likely never approach that!)

However, I\'m wondering if the (relatively) small load
would make the genset\'s \"control\" tougher to keep
on mark?


I don\'t think so but its efficiency at small loads will be horrible.

Aye, there\'s the rub

It appears to me that no-load fuel consumption is around .1 gph per kW
of load plus rating for smallish gasoline units. Diesels would be better,
inverters can be better, maybe bigger is better, but a 4x oversize will bite
pretty hard. To be useful, you have to have fuel on-hand all the time. If
you only need a day\'s endurance, oversizing isn\'t so costly. If you need a
week, it\'s going to be a big tank.

There are several ways of looking at that aspect.

For a day, one could likely live without air conditioning (or heat), could
keep the refrigerator/freezer buttoned up tight (no unnecessary \"browsing\"),
rely on a laptop instead of a workstation, eat canned goods (heat over an
outdoor fire improvised from on-hand fuel stores) opened with a MANUAL
canopener, etc.

For a *week* (disaster?), the toll of living without quickly grows. A
refrigerator/freezer isn\'t going to hold up for extended periods of time
so, plan on doing a LOT of cooking (to salvage stored foods). That puts
a bigger load on some other \"fuel consumer\" -- an outdoor grill, a gas
appliance, etc.

Soon, we won\'t be able to live comfortably without air conditioning (summer
starts in April; we\'ve already hit 100F). This will persist through September
(to varying degrees... worsening during Monsoon as a consequence of the higher
humidity). Even nighttime lows will bottom out in the 80\'s.

[Winter is easier to tolerate power loss as the daytime temperatures
are still 70+ and even cold nights -- 30F -- could be tolerated with
extra layers of clothing]

For a prolonged outage, you have to wonder if your source of
additional fuel will continue to be available. It\'s unlikely
that just your home/neighborhood is suffering, in that case.
Will the local gas station (gasoline/diesel) be able to run
their pumps? Will scheduled deliveries (tankers) continue
uninterrupted? How long will you queue for fuel that is in
shorter supply?

Relying on a vehicle\'s fuel storage ability means you will
be juggling the fuel available in the vehicle as a supply for
the genset vs. as a possible means of departing the area
(or, conducting extended foraging runs if store shelves start
to go bare) if the need arises.

[I wonder what its like in places that get decimated by hurricanes?]

A free generator is the easy third of the problem: You need fuel and
distribution to complete the tripod. If you already have fuel on hand,
then the oversized generator might be a very good deal. If not, the fuel
storage is the hard part.

I actually think the more immediate concerns are (re)deploying a
genset that isn\'t an integral part of your homestead and lifestyle.
Gensets are fine if you are *camping* or living off grid. But, if
they are an *exceptional* source of power, there are often lots
of hassles associated with their use. (would it be easier to just
check in to a hotel for the duration of the outage?)

A portable unit needs to be hauled out to a place where it can
be safely operated without danger of toxic fumes, interference
by neighbors/wildlife (you wouldn\'t want a curious neighborhood
child to be injured \"exploring\" it), protection from the elements,
accessibility (so you can check on it as well as service/refuel it),
etc.

Then, the unit needs to be tethered to the loads. If you\'ve opted
for portable, you\'ve likely not opted to install a bypass. So, run
a (long) cord(s) to the load(s) of interest. Careful not to trip!
(or, accidentally dislodge one!)

[You wouldn\'t want to back-feed the house from a single point without
a disconnect as the risk of mistake is too high. And, the task of
manually connecting -- and isolating the utility -- means \"special\"
skills are needed (not something your other half is likely going to
be keen on doing -- just as they\'d not be keen on wheeling the
genset out to a convenient operating point and running cords)]

And, if you\'ve sized the genset (portable or otherwise) for anything
less than your whole house load, you now have to actively manage
your loads; amusingly, the loads that you\'d typically want to backup
(freezer, refrigerator, HVAC) already have \"automatic controls\"
because managing their use manually would be tediously impractical.
So, you\'d have to remember to turn each of these OFF (assuming they
are then tethered to the genset) and manually divide the available
power amongst them.

[Again, not something that you\'ll want to be doing constantly -- and
likely not a chore that is easily RELIABLY delegated]

Then, someone has to start it (even if electric start) and attend to
it\'s fuel needs. Assuming it has been properly maintained in the
\"off season\".

[You always discover dead batteries in your flashlight when you
NEED the flashlight! :> ]

There\'s an appeal to a TURNKEY whole-house genset plumbed to the
natural gas supply -- assuming THAT is not interrupted! But, that
comes with a high price tag if you also don\'t want to have to
deal with load management, etc.

[\"Quick, everyone... turn off all nonessential loads so the genset
won\'t struggle to come on-line!\"]

I started with a cheap (5kW) generator and gradually realized that UPS units
with overnight endurance for critical loads is a better way to start out.
As it happens, I do have fuel (33gal tank in my car), enough for a few days.
That wasn\'t planning, just dumb luck.

That was our initial strategy; gasoline powered so the gas fueled cars
could act as fuel storage containers that are capable of transporting
themselves to a \"filling station\". You\'d not want to have to lug a
bunch of 5G cans of fuel back and forth!

But, you quickly have to discard many loads for small gensets. Most
loads are really large loads that AVERAGE OUT to smaller loads. But,
a genset would \"see\" the large peak load.

E.g., the 1000W microwave oven is either drawing 1000W or (essentially)
0W. The output power (to the load being heated) is the average of
these. Likewise, an electric stovetop/oven cycles between a few KW
and nothing to maintain a desired temperature setting. Air conditioning,
heating, hot water, refrigeration, etc. are each \"all or nothing\" loads.

So, even if you actively stagger each such load, you still have to
size the genset for the largest of these that you want to use, even
if it is on for a very short duty cycle! E.g., we\'d have to buy a
\"room air conditioner\" to tolerate outages of any length if we couldn\'t
supply the ~12+KW that the ACbrrr requires (neglecting startup current).
That means finding a room that can be isolated from the rest of the
heating/cooling space so the unit could be effective (we have an open
floor plan so we\'d have to choose *a* bedroom as a \"sanctuary\"). And,
storing that device when it isn\'t needed. And, planning on redeploying
it during an outage (running power to it and venting the \"exhaust\" heat
out a nearby window).

If you look at EVERYTHING that is involved, fuel is just *one* of
those annoying little details.

Finally, there\'s no guarantee that you will EVER need this capability!
Or, that when a need arises, you will be able to predict how long the
need will persist to come to an appropriate decision as to whether or
not you want to begin the task of switching to your \"alternate plans\".

I have ~20 UPSs, here. There\'s a 500VA unit that keeps my name/time/font/etc.
server running. Another for SWMBOs computer. A 750VA unit on each of my
6 workstations. A pair of 1.5KVA units to power my monitors. Another pair
of 1.5KVA units to power the SANs. A 1.5KVA for *this* computer and the
internet link. Another for the TV/DVR/DVD. A pair of 2.2KVA units for my
automation system. And a 5KVA unit that will ultimately replace the 2.2KVA
units in their role.

*BATTERIES* become the problem (just like \"fuel\" for the genset).
The batteries for the 5KVA weigh ~400 pounds!

Plus, unlike gasoline/diesel/propane/natural gas, when the batteries run flat,
there\'s no easy way to recharge them in the absence of power!

And, it\'s the same sort of \"manual\" system described for the genset; to use
them (for anything other than their *nominal* applications), you have
to start stringing power cords around the house as their normal loads
aren\'t where you will want to use power when power is scarce!

Much easier in a camping/off-grid situation where the cost and permanence
of the setup is more readily apparent.

The eye of Hurricane Betsy passed over our house. New Orleans was
mostly shut down for two weeks. The streets were impassible with
downed trees and some neighborhoods were flooded. It wasn\'t bad but
much longer would have been.

We were whacked by the 1989 Loma Prieta earthquake, mag 6.9. Power was
out for a couple of days, not too bad.

In both cases, people behaved very well, helping other people.

We were just watching a crew removing trees from a steep hillside
nearby. We have thousands of trees down or about to fall from the
recent rains.

 

[Don Y]

On 4/27/2023 9:34 AM, bob prohaska wrote:

For a day, one could likely live without air conditioning (or heat), could
keep the refrigerator/freezer buttoned up tight (no unnecessary \"browsing\"),
rely on a laptop instead of a workstation, eat canned goods (heat over an
outdoor fire improvised from on-hand fuel stores) opened with a MANUAL
canopener, etc.

The outage duration has huge impact on behavior. When duration is unknown
all decisions (to open the fridge or not) become un-answerable and so a source
of stress. A backup system serves mostly to limit that stress, whether it\'s
called into service or not.

Exactly. Our outages (30 years) have been due to equipment failures
(below grade cabling). The local utility is pretty responsive and,
as we\'ve been to this dance before, we know it will be ~6 hours
regardless of time of day/night.

Of course, we can tell the nature of the problem and how
localized it is by noticing who around us still has power
(\"Sharon\'s got power. And, Alan. But, everyone downstream
from them is in the dark! So, we know the cable from Alan\'s
transformer is at fault.\")

For a *week* (disaster?), the toll of living without quickly grows. A
refrigerator/freezer isn\'t going to hold up for extended periods of time
so, plan on doing a LOT of cooking (to salvage stored foods). That puts
a bigger load on some other \"fuel consumer\" -- an outdoor grill, a gas
appliance, etc.

I\'d put food storage near the top of the backup priority list.

We have about 20 cu ft of freezer capacity, a cupboard full of canned
goods and charcoal for the BBQ.

Soon, we won\'t be able to live comfortably without air conditioning (summer
starts in April; we\'ve already hit 100F). This will persist through September
(to varying degrees... worsening during Monsoon as a consequence of the higher
humidity). Even nighttime lows will bottom out in the 80\'s.

AC is an expensive problem. I\'d aim the for smallest genny that can start it.

So, we\'re in the 10KW+ ballpark -- just for the compressor.

OTOH, if it\'s an outage similar to each of the previous ones
(cables), we can just \"tough it out\" for 6 hours and not have
to deal with it.

Thankfully, we are in a location that is reasonably immune to
natural disasters (historically). If that continues, then the
biggest problem would be a terror attack on a generating or
distribution facility.

[There are reports of people taking potshots at electrical
substations in various places around the country. AFAICT, they
are relatively soft targets so it\'s only a matter of time before
someplace gets screwed...]

For a prolonged outage, you have to wonder if your source of
additional fuel will continue to be available. It\'s unlikely
that just your home/neighborhood is suffering, in that case.
Will the local gas station (gasoline/diesel) be able to run
their pumps? Will scheduled deliveries (tankers) continue
uninterrupted? How long will you queue for fuel that is in
shorter supply?

It\'s easy to imagine intractable scenarios. Look at the history
to see what\'s plausible. For me, that\'s a few days.

Here, the outages have been short (as described above).
And, relatively infrequent.

But, I\'ve lived other places where outages were far more
common (overhead wiring, snow/ice/drunk drivers, etc.).

And, ongoing development is something you can never really
get a handle on as you don\'t know what the net3work\'s
capacity is and how it is distributed.

I\'ve never encountered a natural gas outage before coming here,
so... <shrug>

Relying on a vehicle\'s fuel storage ability means you will
be juggling the fuel available in the vehicle as a supply for
the genset vs. as a possible means of departing the area
(or, conducting extended foraging runs if store shelves start
to go bare) if the need arises.

[I wonder what its like in places that get decimated by hurricanes?]

Either a lot of stored fuel or carefully-chosen compromises in lifestyle
for the duration.

I suspect its a combination of both. And, still no \"guarantee\".
I pity folks who are reliant on power for their health; imagine
the fear when they have to gauge how long their \"backup\" will
support them?

A free generator is the easy third of the problem: You need fuel and
distribution to complete the tripod. If you already have fuel on hand,
then the oversized generator might be a very good deal. If not, the fuel
storage is the hard part.

I actually think the more immediate concerns are (re)deploying a
genset that isn\'t an integral part of your homestead and lifestyle.
Gensets are fine if you are *camping* or living off grid. But, if
they are an *exceptional* source of power, there are often lots
of hassles associated with their use. (would it be easier to just
check in to a hotel for the duration of the outage?)

In the outage, yes absolutely. Planning is the stage to control the hassles.

Yet, you wouldn\'t rush off to a hotel if you expected the outage
to be brief.

And, if it was OBVIOUSLY going to be prolonged, you\'d have to
wonder how many other folks would have similar ideas!

The problem is that it\'s impossible to \"figure the odds\".
\"Past behavior is not a valid predictor of future events\".

A portable unit needs to be hauled out to a place where it can
be safely operated without danger of toxic fumes, interference
by neighbors/wildlife (you wouldn\'t want a curious neighborhood
child to be injured \"exploring\" it), protection from the elements,
accessibility (so you can check on it as well as service/refuel it),
etc.

Then, the unit needs to be tethered to the loads. If you\'ve opted
for portable, you\'ve likely not opted to install a bypass. So, run
a (long) cord(s) to the load(s) of interest. Careful not to trip!
(or, accidentally dislodge one!)

[You wouldn\'t want to back-feed the house from a single point without
a disconnect as the risk of mistake is too high. And, the task of
manually connecting -- and isolating the utility -- means \"special\"
skills are needed (not something your other half is likely going to
be keen on doing -- just as they\'d not be keen on wheeling the
genset out to a convenient operating point and running cords)]

A portable generator interlock and inlet receptable needn\'t be much
work. Being manual it\'s relatively cheap and mostly exempt from NEC
regulation. Automatic systems are a very different story.

You still have to decide what you\'re going to backup -- given
that you\'ll likely not have the power to do the whole house.
If you *don\'t* want to \"run cords\", then that decision is
pretty much immutable.

And, if you\'ve sized the genset (portable or otherwise) for anything
less than your whole house load, you now have to actively manage
your loads; amusingly, the loads that you\'d typically want to backup
(freezer, refrigerator, HVAC) already have \"automatic controls\"
because managing their use manually would be tediously impractical.
So, you\'d have to remember to turn each of these OFF (assuming they
are then tethered to the genset) and manually divide the available
power amongst them.

[Again, not something that you\'ll want to be doing constantly -- and
likely not a chore that is easily RELIABLY delegated]

Then, someone has to start it (even if electric start) and attend to
it\'s fuel needs. Assuming it has been properly maintained in the
\"off season\".

[You always discover dead batteries in your flashlight when you
NEED the flashlight! :> ]

There\'s an appeal to a TURNKEY whole-house genset plumbed to the
natural gas supply -- assuming THAT is not interrupted! But, that
comes with a high price tag if you also don\'t want to have to
deal with load management, etc.

[\"Quick, everyone... turn off all nonessential loads so the genset
won\'t struggle to come on-line!\"]

All of which argues in favor of a grid-backed battery/solar/islanding-
inverter system with a generator as a cherry on top Great if you
have both need and sufficient money.

Exactly. All this for something you HOPE never to need!

WTF?

I started with a cheap (5kW) generator and gradually realized that UPS units
with overnight endurance for critical loads is a better way to start out.
As it happens, I do have fuel (33gal tank in my car), enough for a few days.
That wasn\'t planning, just dumb luck.

That was our initial strategy; gasoline powered so the gas fueled cars
could act as fuel storage containers that are capable of transporting
themselves to a \"filling station\". You\'d not want to have to lug a
bunch of 5G cans of fuel back and forth!

But, you quickly have to discard many loads for small gensets. Most
loads are really large loads that AVERAGE OUT to smaller loads. But,
a genset would \"see\" the large peak load.

E.g., the 1000W microwave oven is either drawing 1000W or (essentially)
0W. The output power (to the load being heated) is the average of
these. Likewise, an electric stovetop/oven cycles between a few KW
and nothing to maintain a desired temperature setting. Air conditioning,
heating, hot water, refrigeration, etc. are each \"all or nothing\" loads.

AC is much worse, the genny has to be sized to starting loads. Stoves
are resistive and much easier. Electric water heat, unless heat-pump,
strikes me as folly in the present day.

Load management appears unavoidable to me.

Unless there is automation to assist in those spontaneous decisions,
you\'ll likely find folks exceeding the available power, simply
because they aren\'t accustomed to having to THINK about how
power is being used. One of the things my automation system
does is handle the scheduling of loads (I\'m instrumenting
every major load in the house). So, it can ensure that the
*big* loads are \"well behaved\". But, I have no control over
anything plugged into a receptacle (too costly to retrofit those
sorts of controls)

[This also applies to other utilities -- like water!]

It also has the hidden benefit of letting the occupants know
what they can do, and when. An electric start genset can be
powered on when you *know* it is needed -- if you can also
coerce the occupants to comply with that schedule.

E.g., \"I need to run the refrigerator for a bit (I know how
long because i watched its consumption previously). If you
would like to make a pot of tea or watch some TV, now would be
a good time to use extra power (on that scale). Definitely
better than some random time when the generator wouldn\'t
be running! (or, when you wouldn\'t *want* it to be running!)\"

When I rewired the kitchen, I thought about which loads were on
each branch circuit and which would likely be operating at the
same time. I didn\'t want to be surprised by the garbage disposal
tripping the breaker used by the dishwasher, etc.

Likewise, I arranged for countertop outlets to be interleaved
so it was intuitive to sort out which branch circuits two
countertop appliances were using -- or sharing.

A neighbor complains that his microwave is always blowing
a breaker -- yeah, because he connected it to a branch circuit
that normally sees a sizeable load. D\'uh...

So, even if you actively stagger each such load, you still have to
size the genset for the largest of these that you want to use, even
if it is on for a very short duty cycle! E.g., we\'d have to buy a
\"room air conditioner\" to tolerate outages of any length if we couldn\'t
supply the ~12+KW that the ACbrrr requires (neglecting startup current).
That means finding a room that can be isolated from the rest of the
heating/cooling space so the unit could be effective (we have an open
floor plan so we\'d have to choose *a* bedroom as a \"sanctuary\"). And,
storing that device when it isn\'t needed. And, planning on redeploying
it during an outage (running power to it and venting the \"exhaust\" heat
out a nearby window).

Mini split heat pump?

Mini splits are eyesores in residences. I think there\'s a market
for minisplit systems that can be RETROFITTED to central HVAC;
locate an evaporator behind each duct opening, plumb the refrigerant
through the ducts, use the central blower to move air through the
evaporator(s)

Here, the easiest solution would be to put a minisplit in the *garage*
and just use it as a place of refuge (move cars out for the duration).
But, that gets the eyesore out of the living area... and puts it
in a place where it is unlikely to ever be used (I don\'t spend
enough time in the garage to warrant cooling it!)

If you look at EVERYTHING that is involved, fuel is just *one* of
those annoying little details.

And, the cost of the generator is the least of the weevils

To a point. At 25KW, a genset plus the load center hookup is
in the $10K region. You have to consider what else you might be
able to get for that same $10K.

Finally, there\'s no guarantee that you will EVER need this capability!
Or, that when a need arises, you will be able to predict how long the
need will persist to come to an appropriate decision as to whether or
not you want to begin the task of switching to your \"alternate plans\".

The only sure benefit of a power backup system is peace of mind.

And only if you need that!

If we lost power for a week, we\'d be annoyed. Inconvenienced. But,
our losses would mainly be monetary (stored food) and aggravational.
We aren\'t going to starve. Or freeze/overheat (if there was a
danger of that, we could get in a car and go to someplace more
hospitable).

OTOH, there\'s no knowing what the future will hold for us. Will we
*need* power for something beyond convenience? A neighbor *needs*
a CPAP. So, I gave her a small UPS to cover those cases where
power fails while she\'s asleep -- or trying to get to sleep.

If, OTOH, she needs to run her oxygen concentrator, that\'s a bigger
load. But, she can resort to bottled gas in an emergency.

I have ~20 UPSs, here. There\'s a 500VA unit that keeps my name/time/font/etc.
server running. Another for SWMBOs computer. A 750VA unit on each of my
6 workstations. A pair of 1.5KVA units to power my monitors. Another pair
of 1.5KVA units to power the SANs. A 1.5KVA for *this* computer and the
internet link. Another for the TV/DVR/DVD. A pair of 2.2KVA units for my
automation system. And a 5KVA unit that will ultimately replace the 2.2KVA
units in their role.

Endurance is the key for UPS units. Most computer units are intended to
allow only a graceful shutdown. I suggest enough battery capacity to let
you ignore outages overnight, at least.

None of my loads are small enough for that (save the name/time/font/etc.
server at ~10W and maybe this machine at ~30W). But, if I\'m *at* a
workstation when power fails, I can take actions to ensure I can remember
what I was doing, at the time (this being the biggest hassle of an outage
in that it interrupts your train of thought, plan of action, etc.).
Anything that is already \"sleeping\" has already saved its state so
when those supplies run down, there\'s nothing lost.

The TV is a nuisance in that I think it will only carry the load
for about an hour -- annoying if you\'re watching a two hour show!
But, there\'s nothing important about TV/film.

*BATTERIES* become the problem (just like \"fuel\" for the genset).
The batteries for the 5KVA weigh ~400 pounds!

Lithium iron phosphate is lighter, longer lasting and faster charging.
Purchase cost is higher, lifetime cost seems comparable to lead-acid.
Backup power is like insurance, it always costs extra.

Of course! Eventually, I will replace the branch circuit that
feeds most of my kit to insert a 2.2KVA unit in series. This
would let me concentrate my battery expenses in one place
instead of having batteries for all these units.

Plus, unlike gasoline/diesel/propane/natural gas, when the batteries run flat,
there\'s no easy way to recharge them in the absence of power!

Desperate times call for desperate measure.....

And, it\'s the same sort of \"manual\" system described for the genset; to use
them (for anything other than their *nominal* applications), you have
to start stringing power cords around the house as their normal loads
aren\'t where you will want to use power when power is scarce!

Individual extension cords are a bad option. A single cord from genny to inlet
receptacle is easier and cheaper than point-of-use cords. A generator interlock
on a main panel can be a DIY project in some jurisdictions, ~1-200$

Again, you then have to sort out what you\'ll power and make a semipermanent
decision. I could opt to move a portable air conditioner to a different
room to suit TODAY\'s needs. Or, opt to backup my workshop instead of
my office, depending on the type of actions I expect to perform.

I have several 100 ft #12AWG and #10AWG \"reels\" (Hannay) so getting power
around the house (from an outside genset) is just inconvenient, not
impossible. But, the reels are heavy so would need *me* to lug them
around in an outage (I don\'t think SWMBO could even lift one and even
on wheels, they are tedious to maneuver)

This plays into the \"how long will it be out\" calculus; do I really
want to drag out the genset AND the cords AND the portable air conditioner
only to discover that the outage will be over in an hour??

Much easier in a camping/off-grid situation where the cost and permanence
of the setup is more readily apparent.

Agreed, but in the end the most realistic setup is likely to be very similar
to a yacht or RV: Closely-sized genset for big intermittent loads, closely
sized inverters and (abundant) batteries for small continuous loads.

Thanks for reading if you got this far!

Anyone with a 4th grade education should be able to read this much! :>

Thanks for the comments!

 

[bob prohaska]

[huge snippage, attributions likely obscured]

Don Y <blockedofcourse@foo.invalid> wrote:

On 4/27/2023 9:34 AM, bob prohaska wrote:

It\'s easy to imagine intractable scenarios. Look at the history
to see what\'s plausible. For me, that\'s a few days.

But, I\'ve lived other places where outages were far more
common (overhead wiring, snow/ice/drunk drivers, etc.).


I\'ve never encountered a natural gas outage before coming here,
so... <shrug

In general, they seem much less common than electrical outages.
The NREL report on fuel choice has, I think, some stats.

Yet, you wouldn\'t rush off to a hotel if you expected the outage
to be brief.

And, if it was OBVIOUSLY going to be prolonged, you\'d have to
wonder how many other folks would have similar ideas!

The problem is that it\'s impossible to \"figure the odds\".
\"Past behavior is not a valid predictor of future events\".

True, but the NREL fuel report has some general information.
In particular, outage frequency versus duration. IIRC, half
of all outages last less than six hours. Battery territory.
You could at least check the utility\'s outage status page
to get a hint what to expect.

A portable generator interlock and inlet receptable needn\'t be much
work. Being manual it\'s relatively cheap and mostly exempt from NEC
regulation. Automatic systems are a very different story.

You still have to decide what you\'re going to backup -- given
that you\'ll likely not have the power to do the whole house.
If you *don\'t* want to \"run cords\", then that decision is
pretty much immutable.

I think this is mistaken, mostly. The interlock provides an
exclusive OR between the generator inlet receptacle and the
utility main disconnect. It backs up the entire panel, you
decide what to turn on manually. You can decide what to power,
and to change generator size/type/fuel at your discretion.
Yes, you do have to manage the loads, but you can change your
mind at any time, not just at installation.

There\'s an appeal to a TURNKEY whole-house genset plumbed to the
natural gas supply -- assuming THAT is not interrupted! But, that
comes with a high price tag if you also don\'t want to have to
deal with load management, etc.

Even a full-house automatic genny needs at least a few seconds
to pick up the load. You\'ll still want UPS (albeit much cheaper)
units to avoid cycling sensitive loads, _and_ the system will
be subject to NEC requirements for sizing/load-shedding logic.

[\"Quick, everyone... turn off all nonessential loads so the genset
won\'t struggle to come on-line!\"]

All of which argues in favor of a grid-backed battery/solar/islanding-
inverter system with a generator as a cherry on top Great if you
have both need and sufficient money.

Exactly. All this for something you HOPE never to need!

A full solar/battery/islanding-inverter system also allows
noon sun to satisfy afternoon peak demand. That can be used
every day to shift peak demand away from the utility. There\'s
a genuine if modest payback. And, the constant exercise means
that faults won\'t go un-noticed.

Load management appears unavoidable to me.

Unless there is automation to assist in those spontaneous decisions,
you\'ll likely find folks exceeding the available power, simply
because they aren\'t accustomed to having to THINK about how
power is being used.

Aye, there\'s the rub again. Folks don\'t want to think about
energy and have largely fallen out of the habit since they
stopped foraging for firewood.

One of the things my automation system
does is handle the scheduling of loads (I\'m instrumenting
every major load in the house). So, it can ensure that the
*big* loads are \"well behaved\". But, I have no control over
anything plugged into a receptacle (too costly to retrofit those
sorts of controls)

Maybe you\'ve already implemented the NEC requirements for automatic
generators.... If so, you\'re in a different spot than I imagined.
In that case a free, hugely oversized generator might very well
be worth trying.

Mini split heat pump?

Mini splits are eyesores in residences. I think there\'s a market
for minisplit systems that can be RETROFITTED to central HVAC;
locate an evaporator behind each duct opening, plumb the refrigerant
through the ducts, use the central blower to move air through the
evaporator(s)

I don\'t get it. Mini-splits cool one room, a central blower forces
air through multiple rooms. What\'s the connection? I agree about
the eyesore part, but this is a tech forum, not esthetics

If you look at EVERYTHING that is involved, fuel is just *one* of
those annoying little details.

For some reason I tand to think of fuel as a major problem, not a
little detail.

And, the cost of the generator is the least of the weevils

To a point. At 25KW, a genset plus the load center hookup is
in the $10K region. You have to consider what else you might be
able to get for that same $10K.

Let\'s suppose the 100kW genny is free. How many gallons in 24 hours
of running at no load does it burn? How much fuel _storage_ will
the money saved on the (reasonably-sized) generator pay for? Can
you physically store that much under your building codes? My 0.1
gph x (load + rated)kW is probably worse than a 100kW unit, so
it\'d help a lot to know the acual no-load fuel burn. Maybe it\'s
less bad than I\'m guessing, but it\'ll still be rather bad.

Endurance is the key for UPS units. Most computer units are intended to
allow only a graceful shutdown. I suggest enough battery capacity to let
you ignore outages overnight, at least.

None of my loads are small enough for that (save the name/time/font/etc.
server at ~10W and maybe this machine at ~30W).

I was thinking of your food storage devices mostly. My fridge draws
100 W, with a duty factor of about 50%. Peak sustained draw is 400 W
for defrost, about 20 min/day. A 100 AH LiFePO4 12 V battery stores
enough energy for overnight operation, with a little margin.

Individual extension cords are a bad option. A single cord from genny to inlet
receptacle is easier and cheaper than point-of-use cords. A generator interlock
on a main panel can be a DIY project in some jurisdictions, ~1-200$

Again, you then have to sort out what you\'ll power and make a semipermanent
decision. I could opt to move a portable air conditioner to a different
room to suit TODAY\'s needs. Or, opt to backup my workshop instead of
my office, depending on the type of actions I expect to perform.

I\'m missing something. With a generator interlock the panel
disconnects from the utility and connects to the genny. All the panel
breakers function as before, so if you move a load, just switch the
corresponding breakers. To power the workshop turn on that breaker
and maybe turn off the office breaker.

This plays into the \"how long will it be out\" calculus; do I really
want to drag out the genset AND the cords AND the portable air conditioner
only to discover that the outage will be over in an hour??

IME, about the time I drag out the genny and string the cords the
power comes back The best available hints will come via outside
communications. To that end I put communications power close to food
storage in priority.

> Thanks for the comments!

You are most welcome.

bob prohaska

 

[Don Y]

On 4/27/2023 9:02 PM, bob prohaska wrote:

Don Y <blockedofcourse@foo.invalid> wrote:
On 4/27/2023 9:34 AM, bob prohaska wrote:

It\'s easy to imagine intractable scenarios. Look at the history
to see what\'s plausible. For me, that\'s a few days.

But, I\'ve lived other places where outages were far more
common (overhead wiring, snow/ice/drunk drivers, etc.).

I\'ve never encountered a natural gas outage before coming here,
so... <shrug

In general, they seem much less common than electrical outages.
The NREL report on fuel choice has, I think, some stats.

All (perinent) stats are local. :>

Where you live IN a service area has a big impact on the
frequency and duration of outages. Some of it has to
do with the type and age of the infrastructure. But, some
also has to do with the \"clout\" of the occupants of those
areas.

We (neighborhood) recently complained to have our streets
repaved. They\'re not \"miserable\" but there are some
persistent potholes (I don\'t think they build with proper
drainage in mind so water gets under the road surface and
leads to failures). It is scheduled for next year.

There are other parts of town (residential areas) where
I can drive the whole car *into* a pothole. They won\'t
see repairs for years!

Yet, you wouldn\'t rush off to a hotel if you expected the outage
to be brief.

And, if it was OBVIOUSLY going to be prolonged, you\'d have to
wonder how many other folks would have similar ideas!

The problem is that it\'s impossible to \"figure the odds\".
\"Past behavior is not a valid predictor of future events\".

True, but the NREL fuel report has some general information.
In particular, outage frequency versus duration. IIRC, half
of all outages last less than six hours. Battery territory.
You could at least check the utility\'s outage status page
to get a hint what to expect.

Battery territory *if* you have a big enough battery and inverter
to handle the load!

With the exception of \"life support\" types of loads, a short
outage is typically just an inconvenience; get a book and
read for a few hours. If after dark, plug in a single LED/CFL
light in each room so you can safely navigate without a flashlight.
Watch videos on a PC instead of the TV, surf the web, listen
to the radio, etc.

All of these are tiny loads.

If you don\'t open the freezer or refrigerator, they\'ll keep
their contents cold for quite a while. And, you can probably
forego that hot meal for 6 hours. So, you don\'t need to
power the *big* loads.

OTOH, if a prolonged/widespread outage, then you have to
rethink your strategy.

If you can\'t *predict* the likely duration (e.g., if you
climb on your roof and all the houses you can see are dark),
then there\'s more uncertainty as to your best course of
action.

And, any tendency to defer that decision just makes it harder to
eventually make.

[E.g., when we had our natgas outage -- at like 1AM -- there was
no information available as to the cause or likely duration.
Nor what they were doing to mitigate it. And, how many of
your neighbors can you telephone at 1AM to ask \"do you have heat?\"]

A portable generator interlock and inlet receptable needn\'t be much
work. Being manual it\'s relatively cheap and mostly exempt from NEC
regulation. Automatic systems are a very different story.

You still have to decide what you\'re going to backup -- given
that you\'ll likely not have the power to do the whole house.
If you *don\'t* want to \"run cords\", then that decision is
pretty much immutable.

I think this is mistaken, mostly. The interlock provides an
exclusive OR between the generator inlet receptacle and the
utility main disconnect. It backs up the entire panel, you
decide what to turn on manually. You can decide what to power,
and to change generator size/type/fuel at your discretion.
Yes, you do have to manage the loads, but you can change your
mind at any time, not just at installation.

Have you thought that out in practical terms? Could your *wife*,
for example, manage this on her own? Will *you* be able to as
you age? What if you are away from the house at the time?

Here, I would have to open every breaker to ensure I was starting
from a known \"no load\" configuration. Then, consult the floorplan
I drew of the house depicting where each branch circuit is used:
Do I need lights in the kitchen? bedroom(s)? bathroom(s)?
Do I need the receptacles in any of these places? What about
the dedicated branch circuits (swamp cooler, oven, ACbrrr,
refrigerator, furnace, washer, dryer)? What is the actual power
requirement of each potential dedicated, switched or pluggable load
I\'m considering?

I have about 100W of \"vampire\" load, here. So, before I turn on
any of those branch circuits, I\'d have to run around and *unplug*
those devices and appliances. All of the TVs, HiFis, household
appliances (I think the garbage disposal is the only appliance
that has a galvanic switch to disconnect it from the mains),
computers, garage door opener, UPSs, printers, NAS/SANs, etc.

[Everything, nowadays, draws power when plugged it]

And, once you\'d settled on the candidate loads, you\'d have
to discipline yourself to abandon your old usage patterns
for anything that *could* be switched on. As well as
disabling those things that you might backup that have their own
\"controllers\" that can switch the device on without your
involvement (refrigerator, HVAC, etc.)

Our refrigerator shit the bed XMAS day. We moved the foodstuffs
into coolers and neighbors\' \"spare refrigerators\" so we didn\'t lose
any foodstuffs or have to live without cold foods/drinks.

But, for the 7 (?) weeks it took to get the new frig delivered,
we would habitually open the DEAD frig\'s door expecting to find
something cold inside -- tripping over the coolers in the
process! People tend to live on autopilot... doing things
mindlessly, out of habit. You have to configure your solution
to tolerate that. \"No, you can\'t use the garage door opener
to exit via the garage. Use the front door *or* plan on
lifting the door manually.\"

There\'s an appeal to a TURNKEY whole-house genset plumbed to the
natural gas supply -- assuming THAT is not interrupted! But, that
comes with a high price tag if you also don\'t want to have to
deal with load management, etc.

Even a full-house automatic genny needs at least a few seconds
to pick up the load. You\'ll still want UPS (albeit much cheaper)
units to avoid cycling sensitive loads, _and_ the system will
be subject to NEC requirements for sizing/load-shedding logic.

Again, you can only power loads that are small enough to be \"carried\"
by your largest (or closest) UPS.

[\"Quick, everyone... turn off all nonessential loads so the genset
won\'t struggle to come on-line!\"]

All of which argues in favor of a grid-backed battery/solar/islanding-
inverter system with a generator as a cherry on top Great if you
have both need and sufficient money.

Exactly. All this for something you HOPE never to need!

A full solar/battery/islanding-inverter system also allows
noon sun to satisfy afternoon peak demand. That can be used
every day to shift peak demand away from the utility. There\'s
a genuine if modest payback. And, the constant exercise means
that faults won\'t go un-noticed.

These have been for sale for months -- presently asking $5900.
Note no solar array included. OR BATTERIES!

---8<---8<---8<---
What is this? - An OutBack Power FLEXpower Radian FPR-8048A-01, 8kW 48VDC Fully
Pre-wired Single Inverter System with two Outback solar charge controllers,
inside a Hoffman Air Conditioned sealed enclosure, suitable for outdoor
placement. Great for off grid, on grid, electrical backup, on grid interactive use.

Just think about the added safety for you, your family and your home by having
all of your solar electronics moved outside of the house into a metal
container, reducing the chance of a house fire.

These are brand new, old stock, that were purchased for a project that never
happened. Unit manufacturing date is 2nd quarter of 2016. There are three
available. They have all been tested and in working condition to, a 6800 watt
load for 1/2 hour, 1200 watts of solar to each solar charge controller, air
conditioner turns on and blows cold air and ran for 1/2 hour .

All components alone exceed $14,000, not including the engineering and assembly
costs that went into these gorgeous units. Don\'t delay buying one, or all, of
these units that allow one to eliminate space taken up inside a house, or
having to listen to that annoying fan noise. Who ever came up with this system
is a genius.

What you get:
- Outback FLEXpower FPR-8048A-01 8,000 Watts 48 Volts for Grid Tie and Off Grid
Systems which includes:
- Outback Power Radian GS8048A-01 Pure Sine Wave Inverter
- 175 Amp DC Inverter Breaker/Disconnect
- MATE3 System Controller and Display, that can be relocated using a CAT5 cable
- FLEXnet DC Battery Monitor
- (2) FLEXmax 80 Amp Charge Controller With Remote Temp. Sensor
- HUB10.3 Communications Manager
- Hoffman 604824 Air Conditioned enclosure
- Conforms to UL 1741 SA
- More, see pictures

This model is intended for both grid-interactive and off-grid (stand alone)
solar power systems. The Outback FLEXpower system comes fully assembled and
tested from the Outback factory. The units are built to meet National Electric
Code standards and designed for ease of installation. Flexpower systems are
available in both off-grid and grid-tie configurations. The systems have been
outfitted with all the necessary wiring, circuit breakers, communications,
battery monitoring and PV ground fault protection. All equipment is ETL listed.

Just add your choice of batteries and solar panels and you will have an
amazing, top of the line system. You will need to drill/punch holes for your
electrical wire needs leading into and out of the stainless steel cabinet, as
well as one for the air conditioner\'s condensate line.

These units weigh approximately 900 lbs. each. and a pallet jack is available
for your loading use.
---8<---8<---8<---

At \"half price\" he still can\'t get a buyer...

Note that it wouldn\'t come close to solving our cooling load.

Load management appears unavoidable to me.

Unless there is automation to assist in those spontaneous decisions,
you\'ll likely find folks exceeding the available power, simply
because they aren\'t accustomed to having to THINK about how
power is being used.

Aye, there\'s the rub again. Folks don\'t want to think about
energy and have largely fallen out of the habit since they
stopped foraging for firewood.

Of course. Convenience trumps all. That\'s why gummits
do things like making \"Energy Star\" certifications
(to incentivize the manufacturer to make products that
are more energy efficient).

If available power was limited (or, if devices always used
\"full\" power), I\'d likely turn OFF devices. And, arrange my
usage so that a device was never wastefully idling.

But, knowing the devices will SLEEP, I won\'t bother to try
to conserve that \"last watt\".

Mini split heat pump?

Mini splits are eyesores in residences. I think there\'s a market
for minisplit systems that can be RETROFITTED to central HVAC;
locate an evaporator behind each duct opening, plumb the refrigerant
through the ducts, use the central blower to move air through the
evaporator(s)

I don\'t get it. Mini-splits cool one room, a central blower forces
air through multiple rooms. What\'s the connection? I agree about
the eyesore part, but this is a tech forum, not esthetics

Put an evaporator (only!) behind each duct vent. No
fan/blower. No cosmetic enclosure. Just stand the
evaporator up so air has to flow THROUGH it.

Thermostatically control when refrigerant is passed
through *that* evaporator. (refrigerant lines are
routed through ductwork to connect to corresponding
to compressor(s)/condenser(s) -- so, no need to cut
holes in walls, etc.)

Whenever ANY evaporator associated with *a* compressor
and condenser calls for cooling, power that compressor.

Whenever ANY compressor is powered, turn on the central
blower (from the old HVAC) to push air through all
of the evaporators that are presently cooling.

Push the air through the evaporators that are calling
for cooling. Draw return air in from wherever it was
drawn by the old HVAC system.

Ideally, add a louvered cover to block the vents that
are NOT calling for cooling so they don\'t draft into
those areas.

If you look at EVERYTHING that is involved, fuel is just *one* of
those annoying little details.

For some reason I tand to think of fuel as a major problem, not a
little detail.

Fuel determines how long you want to carry your load (once
you\'ve opted on a particular load capacity and management
strategy). If you can\'t power your load, then how much
or how little fuel you have on hand is immaterial.

And, the cost of the generator is the least of the weevils

To a point. At 25KW, a genset plus the load center hookup is
in the $10K region. You have to consider what else you might be
able to get for that same $10K.

Let\'s suppose the 100kW genny is free. How many gallons in 24 hours
of running at no load does it burn?

Why would I run it at no load? Shut it down (automatically)
when there is no load. Schedule the loads to maximize its efficiency
when you *do* call on it to run.

Instead of staggering when the air conditioner, refrigerator,
freezer, microwave oven, stovetop, etc. run to fit within the
power budget of a smaller unit, arrange to overlap many of them
in a small window of time. Inform the occupants of your decision
(you being an algorithm) so they can schedule THEIR activities
to fit in this window.

Consider how people subjected to rolling blackouts live.
They don\'t just *discover* \"Oh! We\'ve got power! Quick,
lets cook something!\" Rather, they plan around when
they expect to have power, fitting all of their permitted
loads into that window. They have no power at other times.
And, a genset delivering no power may as well be OFF!

How much fuel _storage_ will
the money saved on the (reasonably-sized) generator pay for? Can
you physically store that much under your building codes? My 0.1
gph x (load + rated)kW is probably worse than a 100kW unit, so
it\'d help a lot to know the acual no-load fuel burn. Maybe it\'s
less bad than I\'m guessing, but it\'ll still be rather bad.

But you don\'t know *how* long you will need/want to run the genset.
If you KNEW that THIS outage was going to be 3 times longer than
your worst case estimate, wouldn\'t you alter how you used the available
fuel? If so, then why not adopt that strategy *now* and triple
your maximum outage period?

What you really care about is fuel consumption for the usage
pattern that you want to support/enforce. Why support a pattern
that calls for the genset to sit idle, BURNING fuel?

Endurance is the key for UPS units. Most computer units are intended to
allow only a graceful shutdown. I suggest enough battery capacity to let
you ignore outages overnight, at least.

None of my loads are small enough for that (save the name/time/font/etc.
server at ~10W and maybe this machine at ~30W).

I was thinking of your food storage devices mostly. My fridge draws
100 W, with a duty factor of about 50%. Peak sustained draw is 400 W
for defrost, about 20 min/day. A 100 AH LiFePO4 12 V battery stores
enough energy for overnight operation, with a little margin.

The fridge will keep things cold for a day -- if you don\'t
BROWSE. Ditto for the (chest) freezer. In my approach,
you\'d reach into the refrigerator and interrupt the
defrost cycle when trying to conserve power. And, chasten
occupants not to open the door(s) until they know EVERYTHING
that they *need* from inside.

[In most households, the refrigerator door is opened more
than ALL of the other doors in the house combined!]

Individual extension cords are a bad option. A single cord from genny to inlet
receptacle is easier and cheaper than point-of-use cords. A generator interlock
on a main panel can be a DIY project in some jurisdictions, ~1-200$

Again, you then have to sort out what you\'ll power and make a semipermanent
decision. I could opt to move a portable air conditioner to a different
room to suit TODAY\'s needs. Or, opt to backup my workshop instead of
my office, depending on the type of actions I expect to perform.

I\'m missing something. With a generator interlock the panel
disconnects from the utility and connects to the genny. All the panel
breakers function as before, so if you move a load, just switch the
corresponding breakers. To power the workshop turn on that breaker
and maybe turn off the office breaker.

But, then EVERYTHING in the workshop has power available
and NONE of the things in the office have power. If you
think you can just rely on \"discipline\" to manage the
loads, then why turn off ANY of the breakers? Just
discipline yourself not to turn on any of those loads!

This doesn\'t work because there are lots of parasitic loads
in most homes that leech power. In addition to this \"drain\" they also
represent *risks* -- that someone will turn one on without thinking of
the power consequences... out of habit (\"on autopilot\")

E.g., most of my workstations are sleeping at any given time.
Yet, I often \"wake one up\", unintentionally, by setting something
on a keyboard (accidentally causing a keystroke to be seen).
Once awake, the PC, I/Os and monitors all consume power until
it goes back to sleep. With power almost always available, this
is just a <grumble> experience -- not worth doing anything
about (\"It\'s only money -- and very little, at that!\")

OTOH, if there was a limit to our *capacity*, then this would
require some immediate fix lest the genset be overloaded by that
relatively large load (three monitors, dual GPU dual Xeon, etc.)

This plays into the \"how long will it be out\" calculus; do I really
want to drag out the genset AND the cords AND the portable air conditioner
only to discover that the outage will be over in an hour??

IME, about the time I drag out the genny and string the cords the
power comes back The best available hints will come via outside
communications. To that end I put communications power close to food
storage in priority.

We\'ve never used our gas-powered genset for similar reasons.
\"Use\" means a fair investment in time NOW plus more, LATER
(cleaning out the remaining gas and prepping for long term
storage). It also announces to the neighbors that I have
that capability (people are notorious for opting not to
take on the tasks and costs of dealing with emergencies
thinking, instead, that they can mooch off someone else who
*has* done so!)

I can *see* homes around me (e.g., the folks who live behind me)
with power so I know the problem is highly localized. And, from
past experience, likely another cable-segment failure.

So, I know to expect a crew to come by and determine which
transformer(s) have primary power (there are audible annunciators
inside so they can hear which ones chirp) to identify the
location of the break. Then, a call to HQ to get permission
to alter the current wiring configuration (isolate the failed
segment; back-feed the isolated loads restoring *my* power).

And, some weeks or months later, removing the failed segment and
installing a new one in its place.

But, past experiences don\'t speak to future ones. I suspect its
only a matter of time before there is an unplanned problem
that results in greater inconvenience.

Amusingly, all of the solar installations here don\'t provide
anything by way of backup power if the utility is offline.
That will be a surprise to the folks who\'ve taken on those
installations!

Thanks for the comments!

You are most welcome.

Its interesting to see the same general *attitude* towards the
problem and the consequences of the uncertainty involved.
And, the consequences of our chosen floorplan, geographic
location, climate, etc. (none of these being things that
were considered in relocating here!)

 

[Tabby]

On Friday, 28 April 2023 at 05:02:53 UTC+1, bob prohaska wrote:

Don Y <blocked...@foo.invalid> wrote:

I\'ve never encountered a natural gas outage before coming here,
so... <shrug

In general, they seem much less common than electrical outages.
The NREL report on fuel choice has, I think, some stats.

In the UK the gas network pipes store about 3 days of normal use. Probably more in the US due to more spread out housing.

 

[Don Y]

On 4/27/2023 9:02 PM, bob prohaska wrote:

To a point. At 25KW, a genset plus the load center hookup is
in the $10K region. You have to consider what else you might be
able to get for that same $10K.

Let\'s suppose the 100kW genny is free. How many gallons in 24 hours
of running at no load does it burn? How much fuel _storage_ will
the money saved on the (reasonably-sized) generator pay for? Can
you physically store that much under your building codes? My 0.1
gph x (load + rated)kW is probably worse than a 100kW unit, so
it\'d help a lot to know the acual no-load fuel burn. Maybe it\'s
less bad than I\'m guessing, but it\'ll still be rather bad.

I started digging deeper. A 35KW unit (diesel) quoted 1G/hr at 9KW load.
A 250KW unit quoted ~4.5G/hr at ~60KW load (no smaller load factors published)

These both seem lower than your prediction. And, the 250 vs 35 ratio
suggests that fuel consumption doesn\'t scale linearly with capacity
(or load).

So, if you can cluster your loads and power the genset on *only*
when they are ready (off at other times), the larger genset seems
to be the more efficient solution.

 

[bob prohaska]

Don Y <blockedofcourse@foo.invalid> wrote:

I started digging deeper. A 35KW unit (diesel) quoted 1G/hr at 9KW load.

That\'s good. A gallon of diesel fuel contains ~50 kWh, so the machine is
about 20% efficient overall at that load.

A 250KW unit quoted ~4.5G/hr at ~60KW load (no smaller load factors
published)

That\'s even better, 37% overall efficiency. Most likely the two figures are
best-case, loaded to peak efficiency.

These both seem lower than your prediction. And, the 250 vs 35 ratio
suggests that fuel consumption doesn\'t scale linearly with capacity
(or load).

My predictions are based on much smaller machines, 1-5 kW, the range I
could reasonably use and store. In heat engines, smaller is worse 8-(
For my generator the best efficiency is about 15%, declining to 0 % at
zero load.

So, if you can cluster your loads and power the genset on *only*
when they are ready (off at other times), the larger genset seems
to be the more efficient solution.

If you can keep the generator usefully loaded near its maximum efficiency,
yes. Perhaps in your case it\'s possible for the 35 kW unit since you
need ~12 kW for A/C. With the 250 kW unit, you\'d have to find a good use
that is sheddable for 60 kW to exploit the efficiency of the genny. Pumping
water to storage might be a good candidate, if you need to pump water....

To estimate parasitic losses the fuel consumption at two different loads
is needed. As the electrical load goes down the parasitics (coolant
pumps, cooling fans, mechanical friction) stay about the same and scale
with the size of the machine. That makes for a very sharp efficiency
cutoff at light loads. And, what makes oversizing a generator undesirable
in most cases.

Thanks for reading,

bob prohaska

 

[Don Y]

On 4/30/2023 2:33 PM, bob prohaska wrote:

Don Y <blockedofcourse@foo.invalid> wrote:

I started digging deeper. A 35KW unit (diesel) quoted 1G/hr at 9KW load.

That\'s good. A gallon of diesel fuel contains ~50 kWh, so the machine is
about 20% efficient overall at that load.

IIRC, at 100% load the figure climbed almost linearly (to 3.7G/hr)
so there aren\'t many efficiency gains left with load sizing.

A 250KW unit quoted ~4.5G/hr at ~60KW load (no smaller load factors
published)

That\'s even better, 37% overall efficiency. Most likely the two figures are
best-case, loaded to peak efficiency.

Most have figures at 25, 50, 75 and 100% loads. The 25-50% figure would
always be closer to where I\'d be operating! :>

These both seem lower than your prediction. And, the 250 vs 35 ratio
suggests that fuel consumption doesn\'t scale linearly with capacity
(or load).

My predictions are based on much smaller machines, 1-5 kW, the range I
could reasonably use and store. In heat engines, smaller is worse 8-(

OK, that makes sense.

For my generator the best efficiency is about 15%, declining to 0 % at
zero load.

Wow! I would have thought it would peak at a higher load factor.

So, if you can cluster your loads and power the genset on *only*
when they are ready (off at other times), the larger genset seems
to be the more efficient solution.

If you can keep the generator usefully loaded near its maximum efficiency,
yes. Perhaps in your case it\'s possible for the 35 kW unit since you
need ~12 kW for A/C.

I have no idea what the locked rotor current is on the compressor.
And, peak surge may threaten a unit even that large -- or the other
loads concurrently powered.

If I am going to \"cluster\" loads, then it would be wise to
apply the compressor load before any others just to give the
most headroom to that and least \"low voltage\" stress on any
others.

But, that means being able to control ALL of the others.

With the 250 kW unit, you\'d have to find a good use
that is sheddable for 60 kW to exploit the efficiency of the genny. Pumping
water to storage might be a good candidate, if you need to pump water....

I only looked at the 250KW unit to get a datapoint \"sufficiently far\"
from the 35KW. That\'s twice the maximum size I would consider (and
the maximum is set by pricing efficiency).

(Obscenely) large units tend to be more industrial in appearance
and performance. E.g., open frames instead of sound-proofed enclosures.
Most seem to have 100+ fuel tanks; the question would then be how long
that fuel could be \"kept\" before it had to be \"consumed\".

To estimate parasitic losses the fuel consumption at two different loads
is needed. As the electrical load goes down the parasitics (coolant
pumps, cooling fans, mechanical friction) stay about the same and scale
with the size of the machine. That makes for a very sharp efficiency
cutoff at light loads. And, what makes oversizing a generator undesirable
in most cases.

Yeah, I\'m just looking for a \"feel\", now. I.e., the idea of trying to
work with an undersized genset seems too much of a hassle. So, the
question becomes \"how big is big enough and how big is TOO big\".

Thanks for reading,

bob prohaska

 

[bob prohaska]

Don Y <blockedofcourse@foo.invalid> wrote:

On 4/30/2023 2:33 PM, bob prohaska wrote:
Don Y <blockedofcourse@foo.invalid> wrote:

For my generator the best efficiency is about 15%, declining to 0 % at
zero load.

Wow! I would have thought it would peak at a higher load factor.

The 15% is at ~5 kW (full load), it\'s an old Miller Legend welder.
Not awful for its size and vintage.

If you can keep the generator usefully loaded near its maximum efficiency,
yes. Perhaps in your case it\'s possible for the 35 kW unit since you
need ~12 kW for A/C.

I have no idea what the locked rotor current is on the compressor.
And, peak surge may threaten a unit even that large -- or the other
loads concurrently powered.

Starting transients are a little different, in that they only last
a few cycles. Most gensets can handle 3x load for that long. Where
I observed trouble was in prompt restart of a fridge. A normal start
was handled ok, but a momentary stoppage followed by a prompt restart
presented the compressor with higher-than-usual initial backpressure.
That made the start surge last much longer than the inverter (in this
case) could handle, putting the system into a sort of death cycle:
Overload, trip, reset, overload, trip .......

This particular problem was self-inflicted and not an issue if I
keep my mitts off the plug when the fridge is running. In a more
complex automatic system it\'s a failure mode to watch out for.

If I am going to \"cluster\" loads, then it would be wise to
apply the compressor load before any others just to give the
most headroom to that and least \"low voltage\" stress on any
others.

But, that means being able to control ALL of the others.

That\'s what makes me hesitant to seek automatic operation, even
in my dreams.

With the 250 kW unit, you\'d have to find a good use
that is sheddable for 60 kW to exploit the efficiency of the genny. Pumping
water to storage might be a good candidate, if you need to pump water....

I only looked at the 250KW unit to get a datapoint \"sufficiently far\"
from the 35KW. That\'s twice the maximum size I would consider (and
the maximum is set by pricing efficiency).

(Obscenely) large units tend to be more industrial in appearance
and performance. E.g., open frames instead of sound-proofed enclosures.
Most seem to have 100+ fuel tanks; the question would then be how long
that fuel could be \"kept\" before it had to be \"consumed\".

To estimate parasitic losses the fuel consumption at two different loads
is needed. As the electrical load goes down the parasitics (coolant
pumps, cooling fans, mechanical friction) stay about the same and scale
with the size of the machine. That makes for a very sharp efficiency
cutoff at light loads. And, what makes oversizing a generator undesirable
in most cases.

Yeah, I\'m just looking for a \"feel\", now. I.e., the idea of trying to
work with an undersized genset seems too much of a hassle. So, the
question becomes \"how big is big enough and how big is TOO big\".

The only thing wrong with \"too big\" is fuel consumption if the genset
is cheap enough. What happens if you figure out how much fuel you can
conveniently store and work from there?

Thanks for reading,

bob prohaska
ps, it wouldn\'t hurt to move this thread over to alt.energy.homepower
you might get more responses

 

[Don Y]

On 4/30/2023 8:04 PM, bob prohaska wrote:

Don Y <blockedofcourse@foo.invalid> wrote:
On 4/30/2023 2:33 PM, bob prohaska wrote:
Don Y <blockedofcourse@foo.invalid> wrote:

For my generator the best efficiency is about 15%, declining to 0 % at
zero load.

Wow! I would have thought it would peak at a higher load factor.

The 15% is at ~5 kW (full load), it\'s an old Miller Legend welder.
Not awful for its size and vintage.

Ah, my mistake. I read that as \"at 15% of CAPACITY you are
most efficient\" -- as we had been talking about % capacity
for the fuel rates.

If you can keep the generator usefully loaded near its maximum efficiency,
yes. Perhaps in your case it\'s possible for the 35 kW unit since you
need ~12 kW for A/C.

I have no idea what the locked rotor current is on the compressor.
And, peak surge may threaten a unit even that large -- or the other
loads concurrently powered.

Starting transients are a little different, in that they only last
a few cycles. Most gensets can handle 3x load for that long. Where

Yeah, but do they maintain voltage and frequency for OTHER loads
on the line during those transients? The fact that the genset doesn\'t
stall is only one issue...

I observed trouble was in prompt restart of a fridge. A normal start
was handled ok, but a momentary stoppage followed by a prompt restart
presented the compressor with higher-than-usual initial backpressure.

Yes, there are \"dead times\" built into many control cycles. The \"control\"
is supposed to enforce these -- but are often implemented incorrectly.

E.g., the delay should *precede* the activation of the compressor, not
follow it.

So, if you interrupt power to the device, the control should force you to
wait -- even if there is NOW a \"call for cooling\" -- before it recognizes
the call. The (incorrect) alternative is to satisfy the call and THEN
implement the delay... before the NEXT call. There doesn\'t seem to
be a difference -- until you think about it in ALL cases!

That made the start surge last much longer than the inverter (in this
case) could handle, putting the system into a sort of death cycle:
Overload, trip, reset, overload, trip .......

Yes, see above. Had the delay been imposed BEFORE, then it would have been
(worst case) overload, trip, reset, delay, overload, trip, reset...

This particular problem was self-inflicted and not an issue if I
keep my mitts off the plug when the fridge is running. In a more
complex automatic system it\'s a failure mode to watch out for.

If I am going to \"cluster\" loads, then it would be wise to
apply the compressor load before any others just to give the
most headroom to that and least \"low voltage\" stress on any
others.

But, that means being able to control ALL of the others.

That\'s what makes me hesitant to seek automatic operation, even
in my dreams.

I would likely use a pair of automatic disconnects:
- one to sever the utility\'s connection to the house
- a second to sever the gensets connection to the
REST of the house

With the 250 kW unit, you\'d have to find a good use
that is sheddable for 60 kW to exploit the efficiency of the genny. Pumping
water to storage might be a good candidate, if you need to pump water....

I only looked at the 250KW unit to get a datapoint \"sufficiently far\"
from the 35KW. That\'s twice the maximum size I would consider (and
the maximum is set by pricing efficiency).

(Obscenely) large units tend to be more industrial in appearance
and performance. E.g., open frames instead of sound-proofed enclosures.
Most seem to have 100+ fuel tanks; the question would then be how long
that fuel could be \"kept\" before it had to be \"consumed\".

To estimate parasitic losses the fuel consumption at two different loads
is needed. As the electrical load goes down the parasitics (coolant
pumps, cooling fans, mechanical friction) stay about the same and scale
with the size of the machine. That makes for a very sharp efficiency
cutoff at light loads. And, what makes oversizing a generator undesirable
in most cases.

Yeah, I\'m just looking for a \"feel\", now. I.e., the idea of trying to
work with an undersized genset seems too much of a hassle. So, the
question becomes \"how big is big enough and how big is TOO big\".

The only thing wrong with \"too big\" is fuel consumption if the genset
is cheap enough. What happens if you figure out how much fuel you can
conveniently store and work from there?

Three issues with storage:
- how much money do you want to tie up in fuel that may not be of use to you
(note that if you periodically run the genset to \"use up\" any \"old\" fuel,
you still get marginal value for the fuel consumed... not as much as if
you could, e.g., burn it in a vehicle
- how much space you want to set aside for fuel storage
- local ordinances regarding fuel storage

The first is just money. If money was the sole concern, you\'d not bother
with a genny!

The second is only an issue for things like propane -- a large, above ground,
free-standing tank. Most of the industrial gensets have tanks in their
bases so the *genset* is the thing that determines the necessary space.

The third likely (?) isn\'t an issue *here* -- cuz AZ is soft on regulating
most things. I\'m sure there are practical restrictions that are related
to safety (and that of your neighbors). But, folks park hummers in their
driveways so having 50G of fuel near a home isn\'t unheard of.

(and, we *do* have farms and other such businesses, here)

Thanks for reading,

bob prohaska
ps, it wouldn\'t hurt to move this thread over to alt.energy.homepower
you might get more responses

I have to start looking into *real* details -- siting, physical size,
running wire to panel, noise level, fuel source/storage, etc.

And, we have to decide if this is our \"forever\" home (I don\'t want
to do this twice!) given the likely climate changes that we\'ll
be experiencing, here.

[But, this is a great time to be thinking about it -- when it\'s 100F
the notion of whether or not you can \"live without\" ACbrrr is much
more \"real\" than when it\'s just 80F/winter]

 

[bob prohaska]

Don Y <blockedofcourse@foo.invalid> wrote:

I have to start looking into *real* details -- siting, physical size,
running wire to panel, noise level, fuel source/storage, etc.

I made (on a much smaller scale) the mistake of buying an inexpensive
engine drive welder and then trying to adapt it to my environment as
a backup generator. It turned out the generator was the least of my
problems in terms of purchase cost. Wiring, fuel storage and noise
were far more difficult to solve. Thanks to modest needs and a big
car gas tank, along with some inverter/chargers and LiFePO4 batteries,
a useful compromise was worked out. But that was a matter of luck,
not clever design.

And, we have to decide if this is our \"forever\" home (I don\'t want
to do this twice!) given the likely climate changes that we\'ll
be experiencing, here.

Or, you could consider it an opportunity to experiment.

[But, this is a great time to be thinking about it -- when it\'s 100F
the notion of whether or not you can \"live without\" ACbrrr is much
more \"real\" than when it\'s just 80F/winter]

Before doing anything else, double glaze and insulate the house.

I\'m in the Sacramento Valley, with a slightly milder climate. I\'ve
fantasized about building a combined micro-CHP system that uses
an absorption chiller driven by a natural gas fired genset. Exhaust
heat would drive the chiller, excess AC power could go to the grid.
On the megawatt scale it might work More realistically, battery
backed islanding solar systems and heat pumps are available now.

Expensive, yes, but no more than the new cars in the neighborhood.

Thanks for reading,

bob prohaska