Induction cooktops, temperature control questions

[Carl]

"Joerg" wrote in message news:glb79tFqdp5U1@mid.individual.net...

On 2019-05-30 16:18, Lasse Langwadt Christensen wrote:
fredag den 31. maj 2019 kl. 01.11.08 UTC+2 skrev Joerg:
On 2019-05-30 15:46, Lasse Langwadt Christensen wrote:
torsdag den 30. maj 2019 kl. 03.53.43 UTC+2 skrev Joseph Gwinn:
On May 29, 2019, Joerg wrote
(in article <gl7msiF3204U1@mid.individual.net&gt:

On 2019-05-29 06:11, Joseph Gwinn wrote:
On May 28, 2019, Joerg wrote
(in article <gl51d5FftnrU1@mid.individual.net&gt:

On 2019-05-27 10:47, Joseph Gwinn wrote:
On May 27, 2019, Joerg wrote
(in article <gl2aggFsd7tU1@mid.individual.net&gt:

On 2019-05-26 12:40, Joseph Gwinn wrote:
On May 26, 2019, Joerg wrote
(in article <gl06onFeclbU1@mid.individual.net&gt:


[...]


Ok, here I meant the cooktops, of course. The pot presents
another
problem as mine isn't induction-suited.

Yep. Most of my pots aren´t either, but some do very well.

That's my issue, the brew kettle is not induction-suited so if I
can't
make that compatible with a steel plate in there induction isn't
going
to work. Mainly because it is tough and probably very expensive
to fin

an induction-suited stainless pot with such a large diameter so
it can
straddle two cooktops.

As has been discussed, one can sit the pot atop a piece of mild
steel th
t
is heated by the induction heater. But that´s way more complex
than an
electric coil, a thermocouple, and an industrial temperature
controller.

It also nixes all the advantages of induction, and then some. You'd
incur roughly the same amount of contact losses plus the power
losses in
the electronics of the induction driver. If a steel plate must be
put
under the pot instead of inside I will stay with traditional
electric
cooktops.

Yep. KISS. Fixed thermostat and coil heater, discussed earlier.
Maybe 220
Vac, for sufficient power for a double batch. No electronics.

Oh, if I could get a large diameter 240 Vac heater at high power and
reasonable cost I'd be happy. It would need to be 3500W or more to
yield
an advantage versus my current setup.

I bet you do not require anything like 3500 watts with good thermal
contact
between pot and heater.

heating 50liters of water from say 5'C to 100'C is going to take

(50000*4,186*95) ~= 20MJ, at 3500W that is roughly 1.5 hour


5C? While we are missing our fair share of global warming it isn't quite
that cold out here

I was guessing the water was straight from the tap


That's typically not so cold. Except maybe during a very hard winter.
Hwoever, to avoid such issues I fill up the pot before I brew and for the
2nd batch in the afternoon I have plastic gallon bottles to fill the kettle
again. Brew equipment doesn't get much of a break here.


If I could get to 1.5h I'd jump for joy.

get a big water heater and preheat the water?


Can't do because it must be run through the big charcoal filter to remove
chlorine and stuff. I could plumb such a filter into the hot water but that
gets involved. Ours isn't that hot to begin with, you can shower on
hot-only without risking scalding. It would also nix the evening pre-fill.
When I get up in the morning I find a pre-filled brew kettle, everything is
wired up, radio thermostat at the ready, and I just turn it all on. Then
brushing teeth, breakfast, a shower, walking the dogs.

How about some insulation for your two burner setup. I'm thinking of a
square sheet metal box with sides and bottom, with holes cut in the bottom
to clear the burners, and tall enough to go halfway up the brew kettle or
more, whatever is convenient relative to the handles on the kettle. Set the
burners on your table, set the box in place, then lower the kettle into the
box so it sits on the burners like it does now. I'd bend it up from 20 ga
304SS but I have access to a nice shop at my last job . You could make a
lid from a flat plate with a hole cut in it that is just a bit bigger than
the kettle, and then slice that in two through the center of the hole and
put a spring clamp on each side to hold the two halves together around the
kettle. Bend the edges down half an inch or so for stiffness. Total weight
probably less than the empty kettle. Try it like that to see how it goes,
then if you have to maybe try adding some insulation but that could get ugly
fast so I'm hoping just the single layer box would be a big help. Hmm, you
could loosely crumple aluminum foil to fill the interior, that would help
the R-value a good bit with no temperature limits or fiber issues from other
insulation materials. If it gets spilled on, throw it out and crumple some
fresh foil . Calculate the heat loss at your running temperature for the
surface area of your kettle and compare that to your burner power; I bet a
little insulation will help a lot.

--
Regards,
Carl Ijames

 

[Joseph Gwinn]

On May 30, 2019, Joerg wrote
(in article <gla8raFjvr9U1@mid.individual.net&gt:

On 2019-05-29 18:53, Joseph Gwinn wrote:
On May 29, 2019, Joerg wrote
(in article <gl7msiF3204U1@mid.individual.net&gt:

On 2019-05-29 06:11, Joseph Gwinn wrote:
On May 28, 2019, Joerg wrote
(in article <gl51d5FftnrU1@mid.individual.net&gt:

On 2019-05-27 10:47, Joseph Gwinn wrote:
On May 27, 2019, Joerg wrote
(in article <gl2aggFsd7tU1@mid.individual.net&gt:

On 2019-05-26 12:40, Joseph Gwinn wrote:
On May 26, 2019, Joerg wrote
(in article <gl06onFeclbU1@mid.individual.net&gt:

On 2019-05-26 09:14, Joseph Gwinn wrote:

[...]

Attach thermostat plate to pot using silicon rubber adhesive.

If I had a material that would improve the coupling between electric
coil and the never 100% even pot bottom that would help a lot. Not for
the thermostats in the cooktops because they are already sufficiently
accurate but for heat transfer.

A sheet of silicon rubber is traditional. Such things are sold in kitchen
stores for various purposes.

Attaching the thermostat with silicon rubber adhesive serves to thermally
connect it to the pot.

This will prevent wind disturbances.

With my cheap Walmart burners I just set the thermostat slightly higher.
Worked every single time so far.



.
[snip]
How big is this monster pot? There are pots big enough to co
k
missionaries.

It's got 16-1/2" or 42cm diameter. It could not be half an inc
sh
rter
or it woudn't straddle my two cooktops.

How deep? I have some dutch ovens that large, but no stockpots.

Total volume is 13 gallons, it's pretty deep.

And 15-3/8" or 39cm deep, from the other email.

This is 108 pounds if full to the top.

I bought it for two reasons. Mainly to straddle two cooktops and then
o
reduce the chance of a boil-over. Those are very messy in brewing.

It's filled with a little over 5-1/2 gallons of filtered water at the
beginning, then malt extract, dry malt extract and other stuff is adde

but at least 1/2 gallon of water boils off as steam.

However, yes, the two cooktops underneath must be able to support a
combined weight of up to 50lbs. I was considering brewing a double-bat
h
a few times and then it would be almost 100lbs but so far haven't done
it. Mostly because the cooktops lack heating power.

Need a jib crane for loading and unloading as well.

Nah, due to lower back issues I always siphon it into the fermenter. It
sits on a foldable dolly for the trip to the temperature-controlled
chamber.

.<https://www.northerntool.com/shop/tools/product_200651805_200651805

May exceed the budget, but the back is safe.

That would result in discussions with SWMBO. However, the siphoning
technique works very well and requires no lifting. When I remove the pot
for cleaning it's empty and light.

[snip]
Ok, here I meant the cooktops, of course. The pot presents ano
her
problem as mine isn't induction-suited.

Yep. Most of my pots aren´t either, but some do very well.

That's my issue, the brew kettle is not induction-suited so if I c
n't
make that compatible with a steel plate in there induction isn't g
ing
to work. Mainly because it is tough and probably very expensive to
fin

an induction-suited stainless pot with such a large diameter so it
can
straddle two cooktops.

As has been discussed, one can sit the pot atop a piece of mild stee
th
t
is heated by the induction heater. But that´s way more complex than an
electric coil, a thermocouple, and an industrial temperature control
er.

It also nixes all the advantages of induction, and then some. You'd
incur roughly the same amount of contact losses plus the power losses
n
the electronics of the induction driver. If a steel plate must be put
under the pot instead of inside I will stay with traditional electric
cooktops.

Yep. KISS. Fixed thermostat and coil heater, discussed earlier. Maybe 22

Vac, for sufficient power for a double batch. No electronics.

Oh, if I could get a large diameter 240 Vac heater at high power and
reasonable cost I'd be happy. It would need to be 3500W or more to yield
an advantage versus my current setup.

I bet you do not require anything like 3500 watts with good thermal contact
between pot and heater.

For heatup of brew water nothing beat kilowatts. Except more kilowatts.
But yes, good thermal contact would improve things. That isn't easy with
electric coil burners and an aluminum pot. Even with stainless pots it
isn't easy unless you have a $300+ version with a thick bottom.

If the pot bottom isn´t thick enough, glue a thicker sheet of soft aluminum
to the bottom, and then the coils to the plate.

..

By heater coil, I meant a coil intended for an electric stove; these are
readily available as spares in Home Depot et al for a few tens of dollars.
But use multiple coils connected in series, so they don´t get red hot and
burn the silicon rubber.

The problem is, this can only work if the contact is intimate and for
that you'd almost have to screw each coil to the bottom of the pot in
several places.

One glues the coils to the pot with silicon rubber adhesive. Nothing else is
required.

..

The other thing that´s needed is a safety thermostat, that will trip and
cut the power if things get too hot. Or, design it to be self limiting,
stabilizing at a safe temperature even if the thermostat is stuck in the
heat-on position.

That is the least of worries.

One problem with automation is loss of attention span.

If one has 3500 watt coils, I would not skip the safety stuff. If for
instance one accidentally turned the power on with an empty pot, the bottom
would probably melt.

Anyway, you seem happy with your current solution.

Joe Gwinn

 

[whit3rd]

On Thursday, May 30, 2019 at 7:38:25 AM UTC-7, Joerg wrote:

On 2019-05-29 18:09, Clifford Heath wrote:

What about a replacement heating coil for a 240V electric range?
There'd have to be some available at 3500W, I think?

I thought about it but that turns the whole thing into a science
project.

On that note, let me recommend wrapping flexible heat tape around the
kettle; a fiberglass wrap to serve as a kettle cozy, and it'll look JUST like
a high-vacuum bakeout in a science lab.

<https://www.briskheat.com/standard-insulated-heating-tapes-b00-3810.html.

 

[Jan Panteltje]

On a sunny day (Thu, 30 May 2019 16:07:10 -0700) it happened Joerg
<news@analogconsultants.com> wrote in <glb60kFq4e5U1@mid.individual.net>:

In Germany "Daniel Duesentrieb", referring to the old term
Duesentriebwerk for jet engine. Whenever a new comic book about them
came out during my childhood I had to have it.

In the Netherlands: 'Willy Wortel' later 'Willie Wortel'.
In Dutch:
https://nl.wikipedia.org/wiki/Willie_Wortel

I liked to read those strips.

 

whit3rd <whit3rd@gmail.com> wrote in
news:e451ff69-1082-4867-aba1-5785e5dfe67a@googlegroups.com:

On Thursday, May 30, 2019 at 7:38:25 AM UTC-7, Joerg wrote:
On 2019-05-29 18:09, Clifford Heath wrote:

What about a replacement heating coil for a 240V electric
range? There'd have to be some available at 3500W, I think?

I thought about it but that turns the whole thing into a science
project.

On that note, let me recommend wrapping flexible heat tape around
the kettle; a fiberglass wrap to serve as a kettle cozy, and it'll
look JUST like a high-vacuum bakeout in a science lab.

https://www.briskheat.com/standard-insulated-heating-tapes-b00-
381
0.html.

Nomex (R) transformer paper can be bought in very high
thicknesses. A couple tenths of an inch. That stuff no burn.

It can be ordered in 4 x 8 foot sheets from a thousandth inch
thickness all the way up the chart. Good stuff for thrmal
insulation/containment. NOT good for any transferrence.

 

Joseph Gwinn <joegwinn@comcast.net> wrote in
news:0001HW.22A0D2FC0205A2157000006822EF@news.giganews.com:

On May 30, 2019, Joerg wrote
(in article <gla8raFjvr9U1@mid.individual.net&gt:

On 2019-05-29 18:53, Joseph Gwinn wrote:
On May 29, 2019, Joerg wrote
(in article <gl7msiF3204U1@mid.individual.net&gt:

On 2019-05-29 06:11, Joseph Gwinn wrote:
On May 28, 2019, Joerg wrote
(in article <gl51d5FftnrU1@mid.individual.net&gt:

On 2019-05-27 10:47, Joseph Gwinn wrote:
On May 27, 2019, Joerg wrote
(in article <gl2aggFsd7tU1@mid.individual.net&gt:

On 2019-05-26 12:40, Joseph Gwinn wrote:
On May 26, 2019, Joerg wrote
(in article <gl06onFeclbU1@mid.individual.net&gt:

On 2019-05-26 09:14, Joseph Gwinn wrote:

[...]

Attach thermostat plate to pot using silicon rubber
adhesive.

If I had a material that would improve the coupling between
electric coil and the never 100% even pot bottom that would
help a lot. Not for the thermostats in the cooktops because
they are already sufficiently accurate but for heat transfer.

A sheet of silicon rubber is traditional. Such things are sold
in kitchen stores for various purposes.

Attaching the thermostat with silicon rubber adhesive serves to
thermally connect it to the pot.

This will prevent wind disturbances.

With my cheap Walmart burners I just set the thermostat slightly
higher. Worked every single time so far.



.
[snip]
How big is this monster pot? There are pots big
enough to co
k
missionaries.

It's got 16-1/2" or 42cm diameter. It could not
be half an inc
sh
rter
or it woudn't straddle my two cooktops.

How deep? I have some dutch ovens that large, but
no stockpots.

Total volume is 13 gallons, it's pretty deep.

And 15-3/8" or 39cm deep, from the other email.

This is 108 pounds if full to the top.

I bought it for two reasons. Mainly to straddle two
cooktops and then
o
reduce the chance of a boil-over. Those are very messy in
brewing.

It's filled with a little over 5-1/2 gallons of filtered
water at the beginning, then malt extract, dry malt
extract and other stuff is adde

but at least 1/2 gallon of water boils off as steam.

However, yes, the two cooktops underneath must be able to
support a combined weight of up to 50lbs. I was
considering brewing a double-bat
h
a few times and then it would be almost 100lbs but so far
haven't done it. Mostly because the cooktops lack heating
power.

Need a jib crane for loading and unloading as well.

Nah, due to lower back issues I always siphon it into the
fermenter. It sits on a foldable dolly for the trip to the
temperature-controlled chamber.

.<https://www.northerntool.com/shop/tools/product_200651805_
2006
51805

May exceed the budget, but the back is safe.

That would result in discussions with SWMBO. However, the
siphoning technique works very well and requires no lifting. When
I remove the pot for cleaning it's empty and light.

[snip]
Ok, here I meant the cooktops, of course. The pot
presents ano
her
problem as mine isn't induction-suited.

Yep. Most of my pots aren´t either, but some do
very well.

That's my issue, the brew kettle is not
induction-suited so if I c
n't
make that compatible with a steel plate in there
induction isn't g
ing
to work. Mainly because it is tough and probably very
expensive to
fin

an induction-suited stainless pot with such a large
diameter so it
can
straddle two cooktops.

As has been discussed, one can sit the pot atop a piece
of mild stee
th
t
is heated by the induction heater. But that´s way more
complex tha
n an
electric coil, a thermocouple, and an industrial
temperature control
er.

It also nixes all the advantages of induction, and then
some. You'd incur roughly the same amount of contact
losses plus the power losses
n
the electronics of the induction driver. If a steel plate
must be put under the pot instead of inside I will stay
with traditional electric cooktops.

Yep. KISS. Fixed thermostat and coil heater, discussed
earlier. Maybe 22

Vac, for sufficient power for a double batch. No
electronics.

Oh, if I could get a large diameter 240 Vac heater at high
power and reasonable cost I'd be happy. It would need to be
3500W or more to yield an advantage versus my current setup.

I bet you do not require anything like 3500 watts with good
thermal contact between pot and heater.

For heatup of brew water nothing beat kilowatts. Except more
kilowatts. But yes, good thermal contact would improve things.
That isn't easy with electric coil burners and an aluminum pot.
Even with stainless pots it isn't easy unless you have a $300+
version with a thick bottom.

If the pot bottom isn´t thick enough, glue a thicker sheet of soft
aluminum to the bottom, and then the coils to the plate.

.
By heater coil, I meant a coil intended for an electric stove;
these are readily available as spares in Home Depot et al for a
few tens of dollars. But use multiple coils connected in
series, so they don´t get red hot
and
burn the silicon rubber.

The problem is, this can only work if the contact is intimate and
for that you'd almost have to screw each coil to the bottom of
the pot in several places.

One glues the coils to the pot with silicon rubber adhesive.
Nothing else is required.

.
The other thing that´s needed is a safety thermostat, that will
trip and cut the power if things get too hot. Or, design it to
be self limiting, stabilizing at a safe temperature even if the
thermostat is stuck in the heat-on position.

That is the least of worries.

One problem with automation is loss of attention span.

If one has 3500 watt coils, I would not skip the safety stuff. If
for instance one accidentally turned the power on with an empty
pot, the bottom would probably melt.

Anyway, you seem happy with your current solution.

Joe Gwinn

You could make the two layer pot idea and place oil with a very high
smoke/flash point in between to mediate the thermal. And that will
certainly be able to pump a pot of water at the boiling point.

 

[Jan Panteltje]

On a sunny day (Fri, 31 May 2019 06:56:45 -0700) it happened Joerg
<news@analogconsultants.com> wrote in <glcq4hF6a47U1@mid.individual.net>:

On 2019-05-30 22:51, Jan Panteltje wrote:
On a sunny day (Thu, 30 May 2019 16:07:10 -0700) it happened Joerg
news@analogconsultants.com> wrote in <glb60kFq4e5U1@mid.individual.net>:

In Germany "Daniel Duesentrieb", referring to the old term
Duesentriebwerk for jet engine. Whenever a new comic book about them
came out during my childhood I had to have it.

In the Netherlands: 'Willy Wortel' later 'Willie Wortel'.
In Dutch:
https://nl.wikipedia.org/wiki/Willie_Wortel

I liked to read those strips.


I tried to keep up my Dutch yesterday, watching VRT news and Urbanus.
Well, that's not exactly Dutch I guess.

I like short Dutch news without a lot of pictures:
https://nos.nl/teletekst#101
click on the page numbers next to the headlines.
You can always get pictures by selecting 'Nieuws' top left.

Bit more info in Dutch from this site:
https://www.nu.nl/

I use an ad blocker....

 

[Joerg]

On 2019-05-30 18:26, Carl wrote:

"Joerg" wrote in message news:glb79tFqdp5U1@mid.individual.net...

On 2019-05-30 16:18, Lasse Langwadt Christensen wrote:
fredag den 31. maj 2019 kl. 01.11.08 UTC+2 skrev Joerg:
On 2019-05-30 15:46, Lasse Langwadt Christensen wrote:
torsdag den 30. maj 2019 kl. 03.53.43 UTC+2 skrev Joseph Gwinn:
On May 29, 2019, Joerg wrote
(in article <gl7msiF3204U1@mid.individual.net&gt:

On 2019-05-29 06:11, Joseph Gwinn wrote:
On May 28, 2019, Joerg wrote
(in article <gl51d5FftnrU1@mid.individual.net&gt:

On 2019-05-27 10:47, Joseph Gwinn wrote:
On May 27, 2019, Joerg wrote
(in article <gl2aggFsd7tU1@mid.individual.net&gt:

On 2019-05-26 12:40, Joseph Gwinn wrote:
On May 26, 2019, Joerg wrote
(in article <gl06onFeclbU1@mid.individual.net&gt:


[...]


Ok, here I meant the cooktops, of course. The pot presents
another
problem as mine isn't induction-suited.

Yep. Most of my pots aren´t either, but some do very well.

That's my issue, the brew kettle is not induction-suited so
if I can't
make that compatible with a steel plate in there induction
isn't going
to work. Mainly because it is tough and probably very
expensive to fin

an induction-suited stainless pot with such a large diameter
so it can
straddle two cooktops.

As has been discussed, one can sit the pot atop a piece of
mild steel th
t
is heated by the induction heater. But that´s way more complex
than an
electric coil, a thermocouple, and an industrial temperature
controller.

It also nixes all the advantages of induction, and then some.
You'd
incur roughly the same amount of contact losses plus the power
losses in
the electronics of the induction driver. If a steel plate must
be put
under the pot instead of inside I will stay with traditional
electric
cooktops.

Yep. KISS. Fixed thermostat and coil heater, discussed earlier.
Maybe 220
Vac, for sufficient power for a double batch. No electronics.

Oh, if I could get a large diameter 240 Vac heater at high power and
reasonable cost I'd be happy. It would need to be 3500W or more
to yield
an advantage versus my current setup.

I bet you do not require anything like 3500 watts with good
thermal contact
between pot and heater.

heating 50liters of water from say 5'C to 100'C is going to take

(50000*4,186*95) ~= 20MJ, at 3500W that is roughly 1.5 hour


5C? While we are missing our fair share of global warming it isn't
quite
that cold out here

I was guessing the water was straight from the tap


That's typically not so cold. Except maybe during a very hard winter.
Hwoever, to avoid such issues I fill up the pot before I brew and for
the 2nd batch in the afternoon I have plastic gallon bottles to fill
the kettle again. Brew equipment doesn't get much of a break here.


If I could get to 1.5h I'd jump for joy.

get a big water heater and preheat the water?


Can't do because it must be run through the big charcoal filter to
remove chlorine and stuff. I could plumb such a filter into the hot
water but that gets involved. Ours isn't that hot to begin with, you
can shower on hot-only without risking scalding. It would also nix the
evening pre-fill. When I get up in the morning I find a pre-filled
brew kettle, everything is wired up, radio thermostat at the ready,
and I just turn it all on. Then brushing teeth, breakfast, a shower,
walking the dogs.

How about some insulation for your two burner setup. I'm thinking of a
square sheet metal box with sides and bottom, with holes cut in the
bottom to clear the burners, and tall enough to go halfway up the brew
kettle or more, whatever is convenient relative to the handles on the
kettle. Set the burners on your table, set the box in place, then lower
the kettle into the box so it sits on the burners like it does now. I'd
bend it up from 20 ga 304SS but I have access to a nice shop at my last
job . You could make a lid from a flat plate with a hole cut in it
that is just a bit bigger than the kettle, and then slice that in two
through the center of the hole and put a spring clamp on each side to
hold the two halves together around the kettle. Bend the edges down
half an inch or so for stiffness. Total weight probably less than the
empty kettle. ...

I though about wrap-round insulation but that box idea could work much
better. Main reason is that you can't have anything with glass fibers or
rock wool around a brew. I could make that box out of wood, shouldn't be
harmed by the fairly modest temperature of a boil. The lower part can be
metal-clad with a spacing in case the direct radiant heat from a burner
is a bit much.

The box can be closed at the bottom and almost has to be, to avoid a
chimney effect which would cool things. I'd probably have to make it
two-piece because the burners must be shimmed precisely so the coils
snug-fit the pot and that only works if you can peek into that space
from the sides.

Thanks for the idea.

... Try it like that to see how it goes, then if you have to
maybe try adding some insulation but that could get ugly fast so I'm
hoping just the single layer box would be a big help. Hmm, you could
loosely crumple aluminum foil to fill the interior, that would help the
R-value a good bit with no temperature limits or fiber issues from other
insulation materials. If it gets spilled on, throw it out and crumple
some fresh foil . Calculate the heat loss at your running
temperature for the surface area of your kettle and compare that to your
burner power; I bet a little insulation will help a lot.

I could gauge it by the time it takes to heat to 155F and from there to
207F (boil). Shortening that time is the only thing that really matters.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 2019-05-30 16:55, Lasse Langwadt Christensen wrote:

fredag den 31. maj 2019 kl. 01.29.07 UTC+2 skrev Joerg:
On 2019-05-30 16:18, Lasse Langwadt Christensen wrote:
fredag den 31. maj 2019 kl. 01.11.08 UTC+2 skrev Joerg:

[...]

If I could get to 1.5h I'd jump for joy.

get a big water heater and preheat the water?


Can't do because it must be run through the big charcoal filter to
remove chlorine and stuff. I could plumb such a filter into the hot
water but that gets involved. Ours isn't that hot to begin with, you can
shower on hot-only without risking scalding. It would also nix the
evening pre-fill. When I get up in the morning I find a pre-filled brew
kettle, everything is wired up, radio thermostat at the ready, and I
just turn it all on. Then brushing teeth, breakfast, a shower, walking
the dogs.


I was thinking an extra water heater just for the brewing, you can get
tankless ones with 10s of kW

Then I'd have to run 240V outside and into the man cave. Doable but lots
of work, long story. For US readers: This house has Zinsco panels where
breakers have almost become unobtanium.

Then I could hang a big industrial immersion heater into the kettle
during heat-up phases. Could be done by making a port in the lid.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 2019-05-30 20:11, Joseph Gwinn wrote:

On May 30, 2019, Joerg wrote
(in article <gla8raFjvr9U1@mid.individual.net&gt:

On 2019-05-29 18:53, Joseph Gwinn wrote:
On May 29, 2019, Joerg wrote
(in article <gl7msiF3204U1@mid.individual.net&gt:

On 2019-05-29 06:11, Joseph Gwinn wrote:
On May 28, 2019, Joerg wrote
(in article <gl51d5FftnrU1@mid.individual.net&gt:

On 2019-05-27 10:47, Joseph Gwinn wrote:
On May 27, 2019, Joerg wrote
(in article <gl2aggFsd7tU1@mid.individual.net&gt:

On 2019-05-26 12:40, Joseph Gwinn wrote:
On May 26, 2019, Joerg wrote
(in article <gl06onFeclbU1@mid.individual.net&gt:

On 2019-05-26 09:14, Joseph Gwinn wrote:

[...]

Attach thermostat plate to pot using silicon rubber adhesive.

If I had a material that would improve the coupling between electric
coil and the never 100% even pot bottom that would help a lot. Not for
the thermostats in the cooktops because they are already sufficiently
accurate but for heat transfer.

A sheet of silicon rubber is traditional. Such things are sold in kitchen
stores for various purposes.

Attaching the thermostat with silicon rubber adhesive serves to thermally
connect it to the pot.

This will prevent wind disturbances.

With my cheap Walmart burners I just set the thermostat slightly higher.
Worked every single time so far.



.
[snip]
How big is this monster pot? There are pots big enough to co
k
missionaries.

It's got 16-1/2" or 42cm diameter. It could not be half an inc
sh
rter
or it woudn't straddle my two cooktops.

How deep? I have some dutch ovens that large, but no stockpots.

Total volume is 13 gallons, it's pretty deep.

And 15-3/8" or 39cm deep, from the other email.

This is 108 pounds if full to the top.

I bought it for two reasons. Mainly to straddle two cooktops and then
o
reduce the chance of a boil-over. Those are very messy in brewing.

It's filled with a little over 5-1/2 gallons of filtered water at the
beginning, then malt extract, dry malt extract and other stuff is adde

but at least 1/2 gallon of water boils off as steam.

However, yes, the two cooktops underneath must be able to support a
combined weight of up to 50lbs. I was considering brewing a double-bat
h
a few times and then it would be almost 100lbs but so far haven't done
it. Mostly because the cooktops lack heating power.

Need a jib crane for loading and unloading as well.

Nah, due to lower back issues I always siphon it into the fermenter. It
sits on a foldable dolly for the trip to the temperature-controlled
chamber.

.<https://www.northerntool.com/shop/tools/product_200651805_200651805

May exceed the budget, but the back is safe.

That would result in discussions with SWMBO. However, the siphoning
technique works very well and requires no lifting. When I remove the pot
for cleaning it's empty and light.

[snip]
Ok, here I meant the cooktops, of course. The pot presents ano
her
problem as mine isn't induction-suited.

Yep. Most of my pots aren´t either, but some do very well.

That's my issue, the brew kettle is not induction-suited so if I c
n't
make that compatible with a steel plate in there induction isn't g
ing
to work. Mainly because it is tough and probably very expensive to
fin

an induction-suited stainless pot with such a large diameter so it
can
straddle two cooktops.

As has been discussed, one can sit the pot atop a piece of mild stee
th
t
is heated by the induction heater. But that´s way more complex than an
electric coil, a thermocouple, and an industrial temperature control
er.

It also nixes all the advantages of induction, and then some. You'd
incur roughly the same amount of contact losses plus the power losses
n
the electronics of the induction driver. If a steel plate must be put
under the pot instead of inside I will stay with traditional electric
cooktops.

Yep. KISS. Fixed thermostat and coil heater, discussed earlier. Maybe 22

Vac, for sufficient power for a double batch. No electronics.

Oh, if I could get a large diameter 240 Vac heater at high power and
reasonable cost I'd be happy. It would need to be 3500W or more to yield
an advantage versus my current setup.

I bet you do not require anything like 3500 watts with good thermal contact
between pot and heater.

For heatup of brew water nothing beat kilowatts. Except more kilowatts.
But yes, good thermal contact would improve things. That isn't easy with
electric coil burners and an aluminum pot. Even with stainless pots it
isn't easy unless you have a $300+ version with a thick bottom.

If the pot bottom isn´t thick enough, glue a thicker sheet of soft aluminum
to the bottom, and then the coils to the plate.

.
By heater coil, I meant a coil intended for an electric stove; these are
readily available as spares in Home Depot et al for a few tens of dollars.
But use multiple coils connected in series, so they don´t get red hot and
burn the silicon rubber.

The problem is, this can only work if the contact is intimate and for
that you'd almost have to screw each coil to the bottom of the pot in
several places.

One glues the coils to the pot with silicon rubber adhesive. Nothing else is
required.

.
The other thing that´s needed is a safety thermostat, that will trip and
cut the power if things get too hot. Or, design it to be self limiting,
stabilizing at a safe temperature even if the thermostat is stuck in the
heat-on position.

That is the least of worries.

One problem with automation is loss of attention span.

If one has 3500 watt coils, I would not skip the safety stuff. If for
instance one accidentally turned the power on with an empty pot, the bottom
would probably melt.

The coil thermostat should then kick in just like it does on regular
electric cooktops.

Anyway, you seem happy with your current solution.

Not really but I am realizing that there may not be another solution
easily achievable.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 2019-05-30 22:43, whit3rd wrote:

On Thursday, May 30, 2019 at 7:38:25 AM UTC-7, Joerg wrote:
On 2019-05-29 18:09, Clifford Heath wrote:

What about a replacement heating coil for a 240V electric range?
There'd have to be some available at 3500W, I think?

I thought about it but that turns the whole thing into a science
project.

On that note, let me recommend wrapping flexible heat tape around the
kettle; a fiberglass wrap to serve as a kettle cozy, and it'll look JUST like
a high-vacuum bakeout in a science lab.

https://www.briskheat.com/standard-insulated-heating-tapes-b00-3810.html.

If it's not glue that can work though it would also need an insulation
wrap if I heat the outside instead of from underneath. The tape might
not take kindly to wrapping and unwrapping for each batch.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 2019-05-30 22:51, Jan Panteltje wrote:

On a sunny day (Thu, 30 May 2019 16:07:10 -0700) it happened Joerg
news@analogconsultants.com> wrote in <glb60kFq4e5U1@mid.individual.net>:

In Germany "Daniel Duesentrieb", referring to the old term
Duesentriebwerk for jet engine. Whenever a new comic book about them
came out during my childhood I had to have it.

In the Netherlands: 'Willy Wortel' later 'Willie Wortel'.
In Dutch:
https://nl.wikipedia.org/wiki/Willie_Wortel

I liked to read those strips.

I tried to keep up my Dutch yesterday, watching VRT news and Urbanus.
Well, that's not exactly Dutch I guess.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 2019-05-31 07:29, Jan Panteltje wrote:

On a sunny day (Fri, 31 May 2019 06:56:45 -0700) it happened Joerg
news@analogconsultants.com> wrote in <glcq4hF6a47U1@mid.individual.net>:

On 2019-05-30 22:51, Jan Panteltje wrote:
On a sunny day (Thu, 30 May 2019 16:07:10 -0700) it happened Joerg
news@analogconsultants.com> wrote in <glb60kFq4e5U1@mid.individual.net>:

In Germany "Daniel Duesentrieb", referring to the old term
Duesentriebwerk for jet engine. Whenever a new comic book about them
came out during my childhood I had to have it.

In the Netherlands: 'Willy Wortel' later 'Willie Wortel'.
In Dutch:
https://nl.wikipedia.org/wiki/Willie_Wortel

I liked to read those strips.


I tried to keep up my Dutch yesterday, watching VRT news and Urbanus.
Well, that's not exactly Dutch I guess.

I like short Dutch news without a lot of pictures:
https://nos.nl/teletekst#101
click on the page numbers next to the headlines.

Ah, Teletekst, that's a blast from the past. It was very efficient, my
dad used it to track our flight when we came for a visit. It was very
limited in content though because they sent it all inside the V-sync
space on TV.

You can always get pictures by selecting 'Nieuws' top left.

In the videos they all have an accent ...

Bit more info in Dutch from this site:
https://www.nu.nl/

That is nice.

I use an ad blocker....

Same here. I like it that NOS lets people decline personalized ads.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Carl]

"Joerg" wrote in message news:glcr71F6hsjU1@mid.individual.net...

On 2019-05-30 18:26, Carl wrote:
"Joerg" wrote in message news:glb79tFqdp5U1@mid.individual.net...

On 2019-05-30 16:18, Lasse Langwadt Christensen wrote:
fredag den 31. maj 2019 kl. 01.11.08 UTC+2 skrev Joerg:
On 2019-05-30 15:46, Lasse Langwadt Christensen wrote:
torsdag den 30. maj 2019 kl. 03.53.43 UTC+2 skrev Joseph Gwinn:
On May 29, 2019, Joerg wrote
(in article <gl7msiF3204U1@mid.individual.net&gt:

On 2019-05-29 06:11, Joseph Gwinn wrote:
On May 28, 2019, Joerg wrote
(in article <gl51d5FftnrU1@mid.individual.net&gt:

On 2019-05-27 10:47, Joseph Gwinn wrote:
On May 27, 2019, Joerg wrote
(in article <gl2aggFsd7tU1@mid.individual.net&gt:

On 2019-05-26 12:40, Joseph Gwinn wrote:
On May 26, 2019, Joerg wrote
(in article <gl06onFeclbU1@mid.individual.net&gt:


[...]


Ok, here I meant the cooktops, of course. The pot presents
another
problem as mine isn't induction-suited.

Yep. Most of my pots aren´t either, but some do very well.

That's my issue, the brew kettle is not induction-suited so
if I can't
make that compatible with a steel plate in there induction
isn't going
to work. Mainly because it is tough and probably very
expensive to fin

an induction-suited stainless pot with such a large diameter
so it can
straddle two cooktops.

As has been discussed, one can sit the pot atop a piece of
mild steel th
t
is heated by the induction heater. But that´s way more complex
than an
electric coil, a thermocouple, and an industrial temperature
controller.

It also nixes all the advantages of induction, and then some.
You'd
incur roughly the same amount of contact losses plus the power
losses in
the electronics of the induction driver. If a steel plate must
be put
under the pot instead of inside I will stay with traditional
electric
cooktops.

Yep. KISS. Fixed thermostat and coil heater, discussed earlier.
Maybe 220
Vac, for sufficient power for a double batch. No electronics.

Oh, if I could get a large diameter 240 Vac heater at high power
and
reasonable cost I'd be happy. It would need to be 3500W or more
to yield
an advantage versus my current setup.

I bet you do not require anything like 3500 watts with good
thermal contact
between pot and heater.

heating 50liters of water from say 5'C to 100'C is going to take

(50000*4,186*95) ~= 20MJ, at 3500W that is roughly 1.5 hour


5C? While we are missing our fair share of global warming it isn't
quite
that cold out here

I was guessing the water was straight from the tap


That's typically not so cold. Except maybe during a very hard winter.
Hwoever, to avoid such issues I fill up the pot before I brew and for
the 2nd batch in the afternoon I have plastic gallon bottles to fill
the kettle again. Brew equipment doesn't get much of a break here.


If I could get to 1.5h I'd jump for joy.

get a big water heater and preheat the water?


Can't do because it must be run through the big charcoal filter to
remove chlorine and stuff. I could plumb such a filter into the hot
water but that gets involved. Ours isn't that hot to begin with, you
can shower on hot-only without risking scalding. It would also nix the
evening pre-fill. When I get up in the morning I find a pre-filled
brew kettle, everything is wired up, radio thermostat at the ready,
and I just turn it all on. Then brushing teeth, breakfast, a shower,
walking the dogs.

How about some insulation for your two burner setup. I'm thinking of a
square sheet metal box with sides and bottom, with holes cut in the
bottom to clear the burners, and tall enough to go halfway up the brew
kettle or more, whatever is convenient relative to the handles on the
kettle. Set the burners on your table, set the box in place, then lower
the kettle into the box so it sits on the burners like it does now. I'd
bend it up from 20 ga 304SS but I have access to a nice shop at my last
job . You could make a lid from a flat plate with a hole cut in it
that is just a bit bigger than the kettle, and then slice that in two
through the center of the hole and put a spring clamp on each side to
hold the two halves together around the kettle. Bend the edges down
half an inch or so for stiffness. Total weight probably less than the
empty kettle. ...


I though about wrap-round insulation but that box idea could work much
better. Main reason is that you can't have anything with glass fibers or
rock wool around a brew. I could make that box out of wood, shouldn't be

Fibrous insulation seemed a really bad idea, that's why I suggested the
crumpled aluminum foil to fill the box around the kettle. I've baked out a
lot of stainless steel ultra high vacuum systems by wrapping with heating
tape then overwrapping with a few loose layers of foil. First time I was
shown that I thought it would be a complete waste of time given the thermal
conductivity of aluminum but it really does work, cutting the heater power
maybe in half.

harmed by the fairly modest temperature of a boil. The lower part can be
metal-clad with a spacing in case the direct radiant heat from a burner is
a bit much.

The box can be closed at the bottom and almost has to be, to avoid a
chimney effect which would cool things. I'd probably have to make it
two-piece because the burners must be shimmed precisely so the coils
snug-fit the pot and that only works if you can peek into that space from
the sides.

Yes, I envisioned a full bottom with only the two holes to fit over the
burner elements to get a decent seal at the bottom, and the simple lid to
close off the top. You could set it up by placing the burners, test fitting
with the empty kettle, then remove kettle, set box over burners, replace
kettle. I thought it best to have metal close to the burners so given that
it seemed easiest to use all metal, but if you are building from what you
have in the scrap stock pile ...

Thanks for the idea.


... Try it like that to see how it goes, then if you have to
maybe try adding some insulation but that could get ugly fast so I'm
hoping just the single layer box would be a big help. Hmm, you could
loosely crumple aluminum foil to fill the interior, that would help the
R-value a good bit with no temperature limits or fiber issues from other
insulation materials. If it gets spilled on, throw it out and crumple
some fresh foil . Calculate the heat loss at your running
temperature for the surface area of your kettle and compare that to your
burner power; I bet a little insulation will help a lot.


I could gauge it by the time it takes to heat to 155F and from there to
207F (boil). Shortening that time is the only thing that really matters.

--
Regards,
Carl Ijames

 

[Joseph Gwinn]

On May 31, 2019, Joerg wrote
(in article <glcqg3F6d64U2@mid.individual.net&gt:

On 2019-05-30 20:11, Joseph Gwinn wrote:
On May 30, 2019, Joerg wrote
(in article <gla8raFjvr9U1@mid.individual.net&gt:

On 2019-05-29 18:53, Joseph Gwinn wrote:
On May 29, 2019, Joerg wrote
(in article <gl7msiF3204U1@mid.individual.net&gt:

On 2019-05-29 06:11, Joseph Gwinn wrote:
On May 28, 2019, Joerg wrote
(in article <gl51d5FftnrU1@mid.individual.net&gt:

On 2019-05-27 10:47, Joseph Gwinn wrote:
On May 27, 2019, Joerg wrote
(in article <gl2aggFsd7tU1@mid.individual.net&gt:

On 2019-05-26 12:40, Joseph Gwinn wrote:
On May 26, 2019, Joerg wrote
(in article <gl06onFeclbU1@mid.individual.net&gt:

On 2019-05-26 09:14, Joseph Gwinn wrote:

[...]

Attach thermostat plate to pot using silicon rubber adhesive.

If I had a material that would improve the coupling between electric
coil and the never 100% even pot bottom that would help a lot. Not for
the thermostats in the cooktops because they are already sufficiently
accurate but for heat transfer.

A sheet of silicon rubber is traditional. Such things are sold in kitchen
stores for various purposes.

Attaching the thermostat with silicon rubber adhesive serves to thermally
connect it to the pot.

This will prevent wind disturbances.

With my cheap Walmart burners I just set the thermostat slightly higher.
Worked every single time so far.



.
[snip]
How big is this monster pot? There are pots big enough to co
k
missionaries.

It's got 16-1/2" or 42cm diameter. It could not be half an inc
sh
rter
or it woudn't straddle my two cooktops.

How deep? I have some dutch ovens that large, but no stockpots.

Total volume is 13 gallons, it's pretty deep.

And 15-3/8" or 39cm deep, from the other email.

This is 108 pounds if full to the top.

I bought it for two reasons. Mainly to straddle two cooktops and then
o
reduce the chance of a boil-over. Those are very messy in brewing.

It's filled with a little over 5-1/2 gallons of filtered water at the
beginning, then malt extract, dry malt extract and other stuff is adde

but at least 1/2 gallon of water boils off as steam.

However, yes, the two cooktops underneath must be able to support a
combined weight of up to 50lbs. I was considering brewing a double-bat
h
a few times and then it would be almost 100lbs but so far haven't done
it. Mostly because the cooktops lack heating power.

Need a jib crane for loading and unloading as well.

Nah, due to lower back issues I always siphon it into the fermenter. It
sits on a foldable dolly for the trip to the temperature-controlled
chamber.

.<https://www.northerntool.com/shop/tools/product_200651805_200651805

May exceed the budget, but the back is safe.

That would result in discussions with SWMBO. However, the siphoning
technique works very well and requires no lifting. When I remove the pot
for cleaning it's empty and light.

[snip]
Ok, here I meant the cooktops, of course. The pot presents ano
her
problem as mine isn't induction-suited.

Yep. Most of my pots aren´t either, but some do very well.

That's my issue, the brew kettle is not induction-suited so if I c
n't
make that compatible with a steel plate in there induction isn't g
ing
to work. Mainly because it is tough and probably very expensive to
fin

an induction-suited stainless pot with such a large diameter so it can
straddle two cooktops.

As has been discussed, one can sit the pot atop a piece of mild stee
th
t
is heated by the induction heater. But that´s way more complex
than
an
electric coil, a thermocouple, and an industrial temperature control
er.

It also nixes all the advantages of induction, and then some. You'd
incur roughly the same amount of contact losses plus the power losses in
the electronics of the induction driver. If a steel plate must be put
under the pot instead of inside I will stay with traditional electric
cooktops.

Yep. KISS. Fixed thermostat and coil heater, discussed earlier. Maybe 220
Vac, for sufficient power for a double batch. No electronics.

Oh, if I could get a large diameter 240 Vac heater at high power and
reasonable cost I'd be happy. It would need to be 3500W or more to yield
an advantage versus my current setup.

I bet you do not require anything like 3500 watts with good thermal
contact
between pot and heater.

For heatup of brew water nothing beat kilowatts. Except more kilowatts.
But yes, good thermal contact would improve things. That isn't easy with
electric coil burners and an aluminum pot. Even with stainless pots it
isn't easy unless you have a $300+ version with a thick bottom.

If the pot bottom isn´t thick enough, glue a thicker sheet of soft
aluminum
to the bottom, and then the coils to the plate.

.
By heater coil, I meant a coil intended for an electric stove; these are
readily available as spares in Home Depot et al for a few tens of dollars.
But use multiple coils connected in series, so they don´t get red hot
and
burn the silicon rubber.

The problem is, this can only work if the contact is intimate and for
that you'd almost have to screw each coil to the bottom of the pot in
several places.

One glues the coils to the pot with silicon rubber adhesive. Nothing else is
required.

.
The other thing that´s needed is a safety thermostat, that will trip
and
cut the power if things get too hot. Or, design it to be self limiting,
stabilizing at a safe temperature even if the thermostat is stuck in the
heat-on position.

That is the least of worries.

One problem with automation is loss of attention span.

If one has 3500 watt coils, I would not skip the safety stuff. If for
instance one accidentally turned the power on with an empty pot, the bottom
would probably melt.

The coil thermostat should then kick in just like it does on regular
electric cooktops.

Not really, as the thermal path is laterally in the aluminum pot bottom, and
the lack of fluid prevents convection, further isolating sensor area from
coil area. And the sensor cannot be too close to the coil, to ensure that in
normal operation the sensor is dominated by the fluid temperature, versus the
coil temperature.

In safety, one also covers the various failure modes, like the sensor
breaking or losing thermal contact with the pot bottom. Industrial
temperature controllers generally incorporate shorted or open sensor trips.
Mechanical loss of thermal contact is hard for the controller to detect. A
common approach is a second sensor that the controller uses to declare
over-temperature and shut down.

For home appliances, a standard requirement is that the appliance not set the
house on fire, even if the controller has shorted so the heater is stuck at
full power for hours. The appliance may or may not survive.

..
Hmm. Would something like this 220-volt European electric hob work:

..<http://www.ecg-electro.eu/products/ecg-ev-2502/>

Or this:

..<https://www.ebay.co.uk/itm/New-Double-Electric-Hot-Plate-Hob-Pro-Portable-
Kitchen-2000w-Cooker-
Hotplate/253460692507?epid=17015796574&hash=item3b036f3e1b:g:hrsAAOSwyz5amDCx>


One could mount the sensor or sensors somewhere between the two hobs.

If the pot bottom is not flat enough, sand it flat using wet-dry sandpaper
face-up on a stone counter.

..

Anyway, you seem happy with your current solution.

Not really but I am realizing that there may not be another solution
easily achievable.

Maybe it’s easier to just buy a microbrewery?

Joe Gwinn

 

[Joerg]

On 2019-05-31 09:31, Joseph Gwinn wrote:

On May 31, 2019, Joerg wrote
(in article <glcqg3F6d64U2@mid.individual.net&gt:

On 2019-05-30 20:11, Joseph Gwinn wrote:
On May 30, 2019, Joerg wrote
(in article <gla8raFjvr9U1@mid.individual.net&gt:

On 2019-05-29 18:53, Joseph Gwinn wrote:
On May 29, 2019, Joerg wrote
(in article <gl7msiF3204U1@mid.individual.net&gt:

On 2019-05-29 06:11, Joseph Gwinn wrote:
On May 28, 2019, Joerg wrote
(in article <gl51d5FftnrU1@mid.individual.net&gt:

[...]

It also nixes all the advantages of induction, and then some. You'd
incur roughly the same amount of contact losses plus the power losses in
the electronics of the induction driver. If a steel plate must be put
under the pot instead of inside I will stay with traditional electric
cooktops.

Yep. KISS. Fixed thermostat and coil heater, discussed earlier. Maybe 220
Vac, for sufficient power for a double batch. No electronics.

Oh, if I could get a large diameter 240 Vac heater at high power and
reasonable cost I'd be happy. It would need to be 3500W or more to yield
an advantage versus my current setup.

I bet you do not require anything like 3500 watts with good thermal
contact
between pot and heater.

For heatup of brew water nothing beat kilowatts. Except more kilowatts.
But yes, good thermal contact would improve things. That isn't easy with
electric coil burners and an aluminum pot. Even with stainless pots it
isn't easy unless you have a $300+ version with a thick bottom.

If the pot bottom isn´t thick enough, glue a thicker sheet of soft
aluminum
to the bottom, and then the coils to the plate.

.
By heater coil, I meant a coil intended for an electric stove; these are
readily available as spares in Home Depot et al for a few tens of dollars.
But use multiple coils connected in series, so they don´t get red hot
and
burn the silicon rubber.

The problem is, this can only work if the contact is intimate and for
that you'd almost have to screw each coil to the bottom of the pot in
several places.

One glues the coils to the pot with silicon rubber adhesive. Nothing else is
required.

.
The other thing that´s needed is a safety thermostat, that will trip
and
cut the power if things get too hot. Or, design it to be self limiting,
stabilizing at a safe temperature even if the thermostat is stuck in the
heat-on position.

That is the least of worries.

One problem with automation is loss of attention span.

If one has 3500 watt coils, I would not skip the safety stuff. If for
instance one accidentally turned the power on with an empty pot, the bottom
would probably melt.

The coil thermostat should then kick in just like it does on regular
electric cooktops.

Not really, as the thermal path is laterally in the aluminum pot bottom, and
the lack of fluid prevents convection, further isolating sensor area from
coil area. And the sensor cannot be too close to the coil, to ensure that in
normal operation the sensor is dominated by the fluid temperature, versus the
coil temperature.

On my current cheap cooktops that's different. If the thermal contact
between coil and pot diminshes or is lost the burner thermostat turns it
off very quickly.

In safety, one also covers the various failure modes, like the sensor
breaking or losing thermal contact with the pot bottom. Industrial
temperature controllers generally incorporate shorted or open sensor trips.
Mechanical loss of thermal contact is hard for the controller to detect. A
common approach is a second sensor that the controller uses to declare
over-temperature and shut down.

For home appliances, a standard requirement is that the appliance not set the
house on fire, even if the controller has shorted so the heater is stuck at
full power for hours. The appliance may or may not survive.

OFten there is a thermofuse in it for such events. That can be a
non-resettable one so if there was no pot and the regular thermostat
failed at the same time the burner would turn off and could never be
used again.

.
Hmm. Would something like this 220-volt European electric hob work:

.<http://www.ecg-electro.eu/products/ecg-ev-2502/

It would but not much power advantages versus my current 2x 1kW. Also,
the large diameter pot would cover the control knobs, makes the hot and
hard to control.

Or this:

.<https://www.ebay.co.uk/itm/New-Double-Electric-Hot-Plate-Hob-Pro-Portable-
Kitchen-2000w-Cooker-
Hotplate/253460692507?epid=17015796574&hash=item3b036f3e1b:g:hrsAAOSwyz5amDCx

Same power as my current burners so no advantage. Two of these, however,
that would give my brew kettle a 50% power boost:

https://www.ebay.co.uk/itm/New-Double-Electric-Hot-Plate-Hob-Pro-Portable-Kitchen-2000w-Cooker-Hotplate/253460692507?epid=17015796574&hash=item3b036f3e1b:g:hrsAAOSwyz5amDCx

Look at the orange glow they drove the coil into. I'd never do that.

One could mount the sensor or sensors somewhere between the two hobs.

If the pot bottom is not flat enough, sand it flat using wet-dry sandpaper
face-up on a stone counter.

The thermostat isn't my problem, that works well. The lack of power is
the issue. That is partly due to the wimpy power circuits in the US. In
America everything is bigger, except that. When we moved here I was
happily setting up a den. When I wanted to print a few pages with my old
European printer ... PHUT ... I sat in the dark. What the heck? Then I
learned that typical residential ciruits over here are a measly
120V/15A. No wonder.

.
Anyway, you seem happy with your current solution.

Not really but I am realizing that there may not be another solution
easily achievable.

Maybe it’s easier to just buy a microbrewery?

Nah, those don't provide much advantage but take a chunk out of the bank
account. I like to brew "by hand" like in the old days.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[whit3rd]

On Friday, May 31, 2019 at 7:00:32 AM UTC-7, Joerg wrote:

On 2019-05-30 22:43, whit3rd wrote:

On that note, let me recommend wrapping flexible heat tape around the
kettle; a fiberglass wrap to serve as a kettle cozy...

If it's not glue that can work though it would also need an insulation
wrap if I heat the outside instead of from underneath. The tape might
not take kindly to wrapping and unwrapping for each batch.

The tapes are commonly re-used; for some apparatus, it is normal to stitch
up a garment (very much like a tea cozy) and lace or snap it into place
for each bake-out. Sidewall heating might work best, however, with a
stirring arrangement so the bottom doesn't get cold.