Two phases to house - loss of neutral

[Trevor Wilson]

kreed wrote:

On Nov 24, 12:40 pm, "Phil Allison" <phi...@tpg.com.au> wrote:
"kreed"

From what I can gather, pretty much every home in the US has a 120v
- 0 - 120v system where the 2x 120v's are 180 degrees out of phase.
Between the 2 phases 240v is available for stoves, air conditioners
etc.

In Australia, most separate homes have a straight single phase 240v
supply, its not common for there to be 2,3 separate phases to the
average house. Therefore the scenario Sylvia mentions is less
likely to occur, as not many people have this multi phase system.

The exception here could be blocks of flats, if the main neutral to
the building fails, and there isn't a good earth, the imbalance
could be a risk.

** There is always a good "earth" available - courtesy of the
water mains in the street being linked to neutral at every premises.

..... Phil


That is true in a lot of cases, however I have noticed with a lot of
newer houses, (in QLD anyway) they are using some kind of either black
or grey pvc or poly pipe for home water mains. To make it worse, it
looks to me to be "crimped" together at joins, sometimes with what
look like soft metal rings but not always.

**It's going to be a lot more popular too. The stuff is around half the
price of copper pipes, is very easy to handle and use.


--
Trevor Wilson
www.rageaudio.com.au

 

[David]

Phil Allison wrote:

The MEN system:

In Australia, AC power delivery uses a system called " Multiple Earth
Neutral " - which requires that the neutral conductors in a premises be
connected to the plumbing system at the distribution board (ie power box).
It also requires that an earth stake be installed for the same purpose, but
some older premises may not have this.

Actually, the Neutral conductors are *NOT* connected to the plumbing
system. The Neutral conductor is connected by the MEN link to the main
earthing conductor, which is connected to the appropriate earth
electrode. AS/NZS 3000 then requires that conductive pipe work be
equipotentially bonded to the main earth conductor or earth terminal or
bar (NOT to the neutral).

David

 

[mike]

William R. Walsh wrote:

Hi!

I've on occasion wondered what would happen if we lost the neutral line.

(speaking from a 110V perspective as I'm in the US where power is delivered
as 2x110 volt hot leads with one neutral)

The voltage between the two fluctuates wildly, that's what. The more heavily
loaded of the two will have a voltage drop while the lightly loaded one goes
up.

CRT computer monitors get the jitters even when things are relatively
normal. I don't know why this is. Damage can occur to devices when they get
nailed with high voltage.

It won't be a huge issue up to a point for simple devices, or those with
autoranging power supplies that may try to compensate. Everything else will
suffer--motors, transformer type power supplies, etc...and your electrican
*should* know that. A fire could start depending upon how badly something
reacts to the over or under voltage.

William (had it happen here some years ago - one TV and a few surge
protectors got burnt. Curiously, the TV was not completely dead afterwards,
just temperamental about turning on when warm.)

I witnessed potentially expensive neutral problems twice, once while
living in Hawaii, and once at my present location
in North Carolina. In Hawaii the house I was staying in had to be
fumigated and while the workers were tenting the house,
they managed to break a partially corroded-thru neutral wire coming
from the power pole, which no one noticed. Upon moving back into the
house, the recently-new refrigerator died a quick death upon being
plugged back in, upon which an electrician was called in, who quickly
located the broken neutral.

The second time was when I'd been living where I am now, and I'd
recently bought a new fridge - after a few months having it
working fine I noticed it was sounding like it was struggling to start
and at the same time some of the lights would get brighter (I guess
they were on the other half of the 240V supply). Not wanting to have
to deal with a dead fridge again, I investigated the incoming power
panel and found the neutral to be rather lose, so I coated it and the
other 2 incoming wires with some Noalox (an anti-aluminum oxidation
compound) and tightened 'em all goot-n-tite. That was about 7 years
ago, no more problems so far.

Mike

 

[Meat Plow]

On Tue, 24 Nov 2009 11:10:26 +1100, Sylvia Else
<sylvia@not.at.this.address>wrote:

I have to phases of power supply to my house - so three power lines, two
phases plus neutral.

I've on occasion wondered what would happen if we lost the neutral line.
It seems to me that we'd then have the voltage between the two phases
across two sets of appliances, one set attached to one phase, and the
other set attached to the other phase, with the two sets in series as a
result of their common connection to the neutral wire. Since the two
sets are unlikely to represent equal loads, the net result would be a
large overvoltage on one set of appliances.

My electrician says it's not an issue, but I can't see why.

Any thoughts?

Sylvia.

Removing the return leg isn't going to cause problems in a properly
wired US home. Don't know about the UK.

 

[Jerry Peters]

In sci.electronics.repair kreed <kenreed1999@gmail.com> wrote:

On Nov 24, 10:10 am, Sylvia Else <syl...@not.at.this.address> wrote:
I have to phases of power supply to my house - so three power lines, two
phases plus neutral.

I've on occasion wondered what would happen if we lost the neutral line.
It seems to me that we'd then have the voltage between the two phases
across two sets of appliances, one set attached to one phase, and the
other set attached to the other phase, with the two sets in series as a
result of their common connection to the neutral wire. Since the two
sets are unlikely to represent equal loads, the net result would be a
large overvoltage on one set of appliances.

My electrician says it's not an issue, but I can't see why.

Any thoughts?

Sylvia.


You are both right and wrong as in the absence of Neutral line, a lot
of the neutral current (imbalance) would probably flow via your earth
stake back to the transformer neutral or to a neighbours neutral via
their earth stake and while its not a perfect situation, imbalance
probably would not be as bad as you might think ?

Of course, if there is a long run through earth (terra firma) back to
the nearest neutral, the soil is really dry, the earth stake is sub-
standard etc etc it might not work very well.





Years and years back I once saw the result of this at a 3 phase
installation at a carnival, we were called out to fix

They would have with them, and take from site to site portable fuse
boxes with a 3 phase plug, going to a box with breakers feeding rows
of power points going to each phase (like in a normal building
installation, but portable). They would plug in all their gear to
these sockets, and plug the 3 phase into the 3 phase sockets provided
at the venues.

Of course, a lot of the carnival workers would probably just plug
things in at random, and who knows what load would be on the end of
each lead. There could also be very large numbers of flashing lights
on one lead too, so the load would be less than perfect, and surely
not anywhere near balanced or stable

One case, the neutral lead broke off. On one phase there was a lot of
damage to computer gear / arcade games (same sort of thing -
switchmode power supplies) etc. Some was just blown fuses, some
worse.
Note, they didn't have the earth and neutral bonded inside the box,
and didn't have a separate earth stake, where in a home fuse box they
would.

2 phase situation like yours would be a similar result, unless the
load was really well balanced, and consisting of mostly NON-switchmode
power supply type devices. The phase with the lowest load would
suffer overvoltage.

This load imbalance and voltage difference would change all the time
as various appliances automatically switch off and on, like fridges,
air cons, electric HWS etc. Light bulbs may blow from overvoltage,
this would also change the balance



Try connecting 12v bulbs of different wattages in series across 24v
and see what happens. The voltage will not be the same across each.
Much the same thing.

I actually had the neutral fail (break) a few years back during a
winter wind-storm. No deleterious effects. The imbalance (neutral)
current was carried by the ground, a copper water pipe that's probably
at least 10 feet below gound level and 20 0r so feet long.

Jerry

 

[Jerry Peters]

D Yuniskis <not.going.to.be@seen.com> wrote:

Sylvia Else wrote:
Phil Allison wrote:
The MEN system:

In Australia, AC power delivery uses a system called " Multiple Earth
Neutral " - which requires that the neutral conductors in a premises
be connected to the plumbing system at the distribution board (ie
power box). It also requires that an earth stake be installed for the
same purpose, but some older premises may not have this.

If as you say, neutral has to be tied to Earth at the premises, then I
can indeed see that the situation might not be so bad.

Grounding the mains to "plumbing" *was* common in the US many
years ago. Now, I believe, you *must* ground to a metal
rod driven into the earth (8 ft?). Note that if the water
meter was removed, your earth-through-plumbing would fail.

You're *supposed* to have a bypass around the meter for just this
reason, or the ground connected before the meter.

Jerry

On the face of it, having significant current flowing from neutral to
Earth would have to indicate a fault. It would be nice for the breakers
to trip in such a situation, but I can't see that they will.

This is how GFCI breakers work -- they watch for current "leaking"
off to ground someplace other than in the "return" conductor.

 

[D Yuniskis]

Jerry Peters wrote:

D Yuniskis <not.going.to.be@seen.com> wrote:
Sylvia Else wrote:
Phil Allison wrote:
The MEN system:

In Australia, AC power delivery uses a system called " Multiple Earth
Neutral " - which requires that the neutral conductors in a premises
be connected to the plumbing system at the distribution board (ie
power box). It also requires that an earth stake be installed for the
same purpose, but some older premises may not have this.
If as you say, neutral has to be tied to Earth at the premises, then I
can indeed see that the situation might not be so bad.
Grounding the mains to "plumbing" *was* common in the US many
years ago. Now, I believe, you *must* ground to a metal
rod driven into the earth (8 ft?). Note that if the water
meter was removed, your earth-through-plumbing would fail.

You're *supposed* to have a bypass around the meter for just this
reason, or the ground connected before the meter.

I haven't checked a *current* CodeBook but I think connections
to water pipes have to be within a few feet of the pipe's entry
to the building, etc. And the water pipe must have a certain
length *in* the soil, etc.

Buildings with metal structural members often have the building
itself earthed. And, of course, rules change depending on the
potential available on each conductor, etc.

But, as I said, I think this is all deprecated as you can't
*count* on having metal pipes to the water main, etc.

 

[Baron]

Phil Allison wrote:

"kreed"

From what I can gather, pretty much every home in the US has a 120v -
0 - 120v system where the 2x 120v's are 180 degrees out of phase.
Between the 2 phases 240v is available for stoves, air conditioners
etc.

In Australia, most separate homes have a straight single phase 240v
supply, its not common for there to be 2,3 separate phases to the
average house. Therefore the scenario Sylvia mentions is less likely
to occur, as not many people have this multi phase system.

The exception here could be blocks of flats, if the main neutral to
the building fails, and there isn't a good earth, the imbalance could
be a risk.


** There is always a good "earth" available - courtesy of the water
mains in the street being linked to neutral at every premises.


..... Phil

Except where plastic is in use. Mine is all plastic and the safety
earth is linked to the armouring on the incoming mains feed cable.

--
Best Regards:
Baron.

 

[Baron]

Meat Plow wrote:

On Tue, 24 Nov 2009 11:10:26 +1100, Sylvia Else
sylvia@not.at.this.address>wrote:

I have to phases of power supply to my house - so three power lines,
two phases plus neutral.

I've on occasion wondered what would happen if we lost the neutral
line. It seems to me that we'd then have the voltage between the two
phases across two sets of appliances, one set attached to one phase,
and the other set attached to the other phase, with the two sets in
series as a result of their common connection to the neutral wire.
Since the two sets are unlikely to represent equal loads, the net
result would be a large overvoltage on one set of appliances.

My electrician says it's not an issue, but I can't see why.

Any thoughts?

Sylvia.

Removing the return leg isn't going to cause problems in a properly
wired US home. Don't know about the UK.

The lights would go out ! Domestic properties usually have just a 240v
single phase feed. Usually you would get a single phase running down
one side of the street and another phase running down the other.

--
Best Regards:
Baron.

 

[Phil Allison]

"David the PEDANTIC TWAT FROM HELL "

Actually, the Neutral conductors are *NOT* connected to the plumbing
system.

** Wot INSANE CRAPOLOGY !!

The Neutral conductor is connected by the MEN link to the main earthing
conductor, which is connected to the appropriate earth electrode.

** Da knee bone's connected to da thigh bone ....

AS/NZS 3000 then requires that conductive pipe work be equipotentially
bonded to the main earth conductor or earth terminal or bar (NOT to the
neutral).

** Folks - you have to forgive David cos he is mentally defective.

Bad genes from his mother and his father.

Congenital autism is a curse....



...... Phil

 

[whit3rd]

On Nov 23, 5:38 pm, D Yuniskis <not.going.to...@seen.com> wrote:

Grounding the mains to "plumbing" *was* common in the US many
years ago.  Now, I believe, you *must* ground to a metal
rod driven into the earth (8 ft?).

Just to be clear, my copy of the US National Electric Code clearly
requires (section 250-80) plumbing to be bonded to the electrical
service
ground, it just doesn't allow the buried water piping to substitute
for
a ground rod or similar to-the-soil connection.

The ground wire from the interior water pipe grounds the pipes, not
the
electric wiring.

 

[terryc]

On Tue, 24 Nov 2009 13:40:46 +1100, Phil Allison wrote:

** There is always a good "earth" available - courtesy of the water
mains in the street being linked to neutral at every premises.

Is this something new(<40 yrs) in the Standards in Australia?
No plumbing link here. Just an earth stake under the box.

 

[Sylvia Else]

Baron wrote:

Meat Plow wrote:

On Tue, 24 Nov 2009 11:10:26 +1100, Sylvia Else
sylvia@not.at.this.address>wrote:

I have to phases of power supply to my house - so three power lines,
two phases plus neutral.

I've on occasion wondered what would happen if we lost the neutral
line. It seems to me that we'd then have the voltage between the two
phases across two sets of appliances, one set attached to one phase,
and the other set attached to the other phase, with the two sets in
series as a result of their common connection to the neutral wire.
Since the two sets are unlikely to represent equal loads, the net
result would be a large overvoltage on one set of appliances.

My electrician says it's not an issue, but I can't see why.

Any thoughts?

Sylvia.
Removing the return leg isn't going to cause problems in a properly
wired US home. Don't know about the UK.

The lights would go out ! Domestic properties usually have just a 240v
single phase feed. Usually you would get a single phase running down
one side of the street and another phase running down the other.

I said I have two phases.

Sylvia.

 

[David Brodbeck]

kreed wrote:

You are both right and wrong as in the absence of Neutral line, a lot
of the neutral current (imbalance) would probably flow via your earth
stake back to the transformer neutral or to a neighbours neutral via
their earth stake and while its not a perfect situation, imbalance
probably would not be as bad as you might think ?

Of course, if there is a long run through earth (terra firma) back to
the nearest neutral, the soil is really dry, the earth stake is sub-
standard etc etc it might not work very well.

Sometimes, just to make things really exciting, some of the neutral
current flows over alternate paths to a neighbor's house. These
alternate paths can include things like cable TV shields.

 

[David Nebenzahl]

On 11/23/2009 7:43 PM D Yuniskis spake thus:

Phil Allison wrote:

** In the US and Canada - it is NOT permitted to link neutral and earth
or plumbing within a premises.

"*within* a premises". The neutral *is* "earthed" right outside
the home, typically. The Code goes to great lengths telling
you exactly *how* to earth the mains at the service entrance.

However, this ignores the fact that most residential wiring
is grandfathered into "acceptance". Previously, homes *were*
grounded through their "water main" (e.g., my parents home
has ground at the water meter).

Grounding a home's electrical system through the plumbing is perfectly
safe, and probably the best way to do it, assuming the plumbing is steel
or copper.

This is no longer permitted according to the NEC (American electrical
code). Why? Because not all pipe nowadays is steel or copper. In fact,
one can get into great trouble replumbing part of a house with plastic
and severing an old ground connection.

So, you can encounter all sorts of different situations
here in the US (I've even worked on homes with knob & tube
wiring!)

I've worked on lots of knob and tube wiring around here (San Francisco
Bay area). It's actually a very good wiring system, and in most cases is
still perfectly safe and functional 60 to 80 years later. It's permitted
to be "grandfathered" in under the NEC, but of course is no longer
installed anymore.


--
I am a Canadian who was born and raised in The Netherlands. I live on
Planet Earth on a spot of land called Canada. We have noisy neighbours.

- harvested from Usenet

 

[baron]

Sylvia Else Inscribed thus:

Baron wrote:

Removing the return leg isn't going to cause problems in a properly
wired US home. Don't know about the UK.

The lights would go out ! Domestic properties usually have just a
240v
single phase feed. Usually you would get a single phase running down
one side of the street and another phase running down the other.


I said I have two phases.

Sylvia.

Yes I know ! I answered the question above !

--
Best Regards:
Baron.

 

[Sylvia Else]

baron wrote:

Sylvia Else Inscribed thus:

Baron wrote:

Removing the return leg isn't going to cause problems in a properly
wired US home. Don't know about the UK.
The lights would go out ! Domestic properties usually have just a
240v
single phase feed. Usually you would get a single phase running down
one side of the street and another phase running down the other.

I said I have two phases.

Sylvia.

Yes I know ! I answered the question above !

You think I'm mistaken about having two phases?

Sylvia.

 

[David]

Phil Allison the unqualified drop out wrote:

Actually, the Neutral conductors are *NOT* connected to the plumbing
system.

** Wot INSANE CRAPOLOGY !!

The Neutral conductor is connected by the MEN link to the main earthing
conductor, which is connected to the appropriate earth electrode.

** Da knee bone's connected to da thigh bone ....

But the Neutral not connected to the water pipe....

AS/NZS 3000 then requires that conductive pipe work be equipotentially
bonded to the main earth conductor or earth terminal or bar (NOT to the
neutral).

This should explain it for you Phil. Not too technical.

http://www.standards.org.au/downloads/080725_Electrical_Earthing_Standards_Alert.pdf


David

 

[Phil Allison]

"David the PEDANTIC TWAT FROM HELL "

Actually, the Neutral conductors are *NOT* connected to the plumbing
system.

** Wot INSANE CRAPOLOGY !!

The Neutral conductor is connected by the MEN link to the main earthing
conductor, which is connected to the appropriate earth electrode.

** Da knee bone's connected to da thigh bone ....

AS/NZS 3000 then requires that conductive pipe work be equipotentially
bonded to the main earth conductor or earth terminal or bar (NOT to the
neutral).

** Folks - you have to forgive David cos he is mentally defective.

Bad genes from his mother and his father.

Congenital autism is a curse.

This dude is is TOTALLY FUCKED WITH IT.



...... Phil

 

[whit3rd]

On Nov 24, 7:54 am, Meat Plow <m...@petitmorte.net> wrote:

Removing the return leg isn't going to cause problems in a properly
wired US home. Don't know about the UK.

That's just false. A properly wired US home without a neutral
wire to the transformer has 240V across both phases, which
can leave either phase anywhere from zero to 240 VAC. Damage
to 120V appliances will result unless the breakers trip first.

The 'ground' connection would have to carry the whole house's
current imbalance load in place of that neutral, through the earth to
some nearby dwelling that DOES have a proper neutral wire,
to the same pole-pig transformer, for this calamity not to occur.