The baseboard heat in one of the bedrooms trips the breaker as soon as
I turn the thermostat on. We didn't know this until now because it
didn't get cold enough to need it until now.

But wait, there's more. The house (we just moved) had fuses until the
panel was replaced with a modern looking circuit breaker panel. We
tested that heater on inspection but that was while it was still on
fuses. I never thought to try it with the new panel.

The electrician says most likely bad thermostat, he'll come back and
look when he can schedule it, may be a while.

If so, I'd like to know what in a thermostat goes bad like that. I'm
not sure how they're wired inside.

I put a meter on the thermostat. The stat has four terminals, two
marked line and two marked load. With breaker off and stat off, I
read 28 ohms across load. That sounds reasonable, it should pull 8.6
amps if my math is correct, and the 20 A breaker should be fine.
Breaker off and stat on, 26.7 ohms appears across both load terminals
and line terminals, that sounds okay to me too, .8 and .7 ohms from
line to load across the contacts.

With the power on, I read 242 VAC across line, 0 across load, 120 from
each line terminal to load terminal, 120 from each line terminal to
ground. I didn't expect that. I thought a thermostat this old would
be single pole, and so one load terminal would read zero. That's with
the thermostat turned off, if I turn it on it trips the breaker
immediately. Can this be a double pole stat? or am I just
misunderstanding the readings?

Curious symptom: with the breaker off, I still read 1.12 VAC across
line, 2.66 from line to one load terminal, 1.48 to another. It's a
radio shack DMM, and I've always assumed low voltage readings like
that were due to some kind of capacitative coupling, not real. Maybe
not?

Anyway, heater sounds okay at 28 ohms, so it should be the thermostat
or the breaker. But there would have to be a dead short in it to trip
the breaker immediately, shouldn't that show up on the resistance
readings?

Any more diagnostic suggestions? What else to try? I'm still
suspicious of the breaker, that's the only thing known to have
changed.

TimR wrote:
The baseboard heat in one of the bedrooms trips the breaker as soon as
I turn the thermostat on. We didn't know this until now because it
didn't get cold enough to need it until now.

But wait, there's more. The house (we just moved) had fuses until the
panel was replaced with a modern looking circuit breaker panel. We
tested that heater on inspection but that was while it was still on
fuses. I never thought to try it with the new panel.

The electrician says most likely bad thermostat, he'll come back and
look when he can schedule it, may be a while.

If so, I'd like to know what in a thermostat goes bad like that. I'm
not sure how they're wired inside.

I put a meter on the thermostat. The stat has four terminals, two
marked line and two marked load. With breaker off and stat off, I
read 28 ohms across load. That sounds reasonable, it should pull 8.6
amps if my math is correct, and the 20 A breaker should be fine.
Breaker off and stat on, 26.7 ohms appears across both load terminals
and line terminals, that sounds okay to me too, .8 and .7 ohms from
line to load across the contacts.

With the power on, I read 242 VAC across line, 0 across load, 120 from
each line terminal to load terminal, 120 from each line terminal to
ground. I didn't expect that. I thought a thermostat this old would
be single pole, and so one load terminal would read zero. That's with
the thermostat turned off, if I turn it on it trips the breaker
immediately. Can this be a double pole stat? or am I just
misunderstanding the readings?

Curious symptom: with the breaker off, I still read 1.12 VAC across
line, 2.66 from line to one load terminal, 1.48 to another. It's a
radio shack DMM, and I've always assumed low voltage readings like
that were due to some kind of capacitative coupling, not real. Maybe
not?

Anyway, heater sounds okay at 28 ohms, so it should be the thermostat
or the breaker. But there would have to be a dead short in it to trip
the breaker immediately, shouldn't that show up on the resistance
readings?

Any more diagnostic suggestions? What else to try? I'm still
suspicious of the breaker, that's the only thing known to have
changed.
Hi,
Be logical. If it worked with fuse OK and now breaker trips wouldn't it
mean the breaker is under rated? What is in there now?

TimR wrote:

The baseboard heat in one of the bedrooms trips the breaker as soon as
I turn the thermostat on. We didn't know this until now because it
didn't get cold enough to need it until now.

But wait, there's more. The house (we just moved) had fuses until the
panel was replaced with a modern looking circuit breaker panel. We
tested that heater on inspection but that was while it was still on
fuses. I never thought to try it with the new panel.

The electrician says most likely bad thermostat, he'll come back and
look when he can schedule it, may be a while.

If so, I'd like to know what in a thermostat goes bad like that. I'm
not sure how they're wired inside.

I put a meter on the thermostat. The stat has four terminals, two
marked line and two marked load. With breaker off and stat off, I
read 28 ohms across load. That sounds reasonable, it should pull 8.6
amps if my math is correct, and the 20 A breaker should be fine.
Breaker off and stat on, 26.7 ohms appears across both load terminals
and line terminals, that sounds okay to me too, .8 and .7 ohms from
line to load across the contacts.

With the power on, I read 242 VAC across line, 0 across load, 120 from
each line terminal to load terminal, 120 from each line terminal to
ground. I didn't expect that. I thought a thermostat this old would
be single pole, and so one load terminal would read zero. That's with
the thermostat turned off, if I turn it on it trips the breaker
immediately. Can this be a double pole stat? or am I just
misunderstanding the readings?

Curious symptom: with the breaker off, I still read 1.12 VAC across
line, 2.66 from line to one load terminal, 1.48 to another. It's a
radio shack DMM, and I've always assumed low voltage readings like
that were due to some kind of capacitative coupling, not real. Maybe
not?

Anyway, heater sounds okay at 28 ohms, so it should be the thermostat
or the breaker. But there would have to be a dead short in it to trip
the breaker immediately, shouldn't that show up on the resistance
readings?

Any more diagnostic suggestions? What else to try? I'm still
suspicious of the breaker, that's the only thing known to have
changed.


Quote: "With the power on, I read 242 VAC across line, 0 across
load, 120 from each line terminal to load terminal"

120 from Line to Load may be the clue.

Difficult to be certain with a sensitive meter though.
Repeat that test using a 120V lamp in place of the meter.

If the test lamp lights, the heater element is shorted to
the sheath (or there is a wiring fault to Ground).

Jim

On Nov 21, 8:02�pm, Speedy Jim wrote:
TimR wrote:
The baseboard heat in one of the bedrooms trips the breaker as soon as
I turn the thermostat on. �We didn't know this until now because it
didn't get cold enough to need it until now.

But wait, there's more. �The house (we just moved) had fuses until the
panel was replaced with a modern looking circuit breaker panel. �We
tested that heater on inspection but that was while it was still on
fuses. �I never thought to try it with the new panel.

The electrician says most likely bad thermostat, he'll come back and
look when he can schedule it, may be a while.

If so, I'd like to know what in a thermostat goes bad like that. �I'm
not sure how they're wired inside.

I put a meter on the thermostat. �The stat has four terminals, two
marked line and two marked load. �With breaker off and stat off, I
read 28 ohms across load. �That sounds reasonable, it should pull 8.6
amps if my math is correct, and the 20 A breaker should be fine.
Breaker off and stat on, 26.7 ohms appears across both load terminals
and line terminals, that sounds okay to me too, .8 and .7 ohms from
line to load across the contacts.

With the power on, I read 242 VAC across line, 0 across load, 120 from
each line terminal to load terminal, 120 from each line terminal to
ground. �I didn't expect that. �I thought a thermostat this old would
be single pole, and so one load terminal would read zero. �That's with
the thermostat turned off, if I turn it on it trips the breaker
immediately. �Can this be a double pole stat? �or am I just
misunderstanding the readings?

Curious symptom: �with the breaker off, I still read 1.12 VAC across
line, 2.66 from line to one load terminal, 1.48 to another. �It's a
radio shack DMM, and I've always assumed low voltage readings like
that were due to some kind of capacitative coupling, not real. �Maybe
not?

Anyway, heater sounds okay at 28 ohms, so it should be the thermostat
or the breaker. �But there would have to be a dead short in it to trip
the breaker immediately, shouldn't that show up on the resistance
readings?

Any more diagnostic suggestions? � What else to try? �I'm still
suspicious of the breaker, that's the only thing known to have
changed.

� � Quote: �"With the power on, I read 242 VAC across line, 0 across
� � load, 120 from each line terminal to load terminal"

120 from Line to Load may be the clue.

Difficult to be certain with a sensitive meter though.
Repeat that test using a 120V lamp in place of the meter.

If the test lamp lights, the heater element is shorted to
the sheath (or there is a wiring fault to Ground).

Jim- Hide quoted text -

- Show quoted text -

yeah DONT use digital meters for this sort of testing......

light bulb or analog meter

digitals too sensitive give capacitive coupled readings

On Nov 21, 8:02*pm, Speedy Jim wrote:
TimR wrote:
The baseboard heat in one of the bedrooms trips the breaker as soon as
I turn the thermostat on. *We didn't know this until now because it
didn't get cold enough to need it until now.

But wait, there's more. *The house (we just moved) had fuses until the
panel was replaced with a modern looking circuit breaker panel. *We
tested that heater on inspection but that was while it was still on
fuses. *I never thought to try it with the new panel.

The electrician says most likely bad thermostat, he'll come back and
look when he can schedule it, may be a while.

If so, I'd like to know what in a thermostat goes bad like that. *I'm
not sure how they're wired inside.

I put a meter on the thermostat. *The stat has four terminals, two
marked line and two marked load. *With breaker off and stat off, I
read 28 ohms across load. *That sounds reasonable, it should pull 8.6
amps if my math is correct, and the 20 A breaker should be fine.
Breaker off and stat on, 26.7 ohms appears across both load terminals
and line terminals, that sounds okay to me too, .8 and .7 ohms from
line to load across the contacts.

With the power on, I read 242 VAC across line, 0 across load, 120 from
each line terminal to load terminal, 120 from each line terminal to
ground. *I didn't expect that. *I thought a thermostat this old would
be single pole, and so one load terminal would read zero. *That's with
the thermostat turned off, if I turn it on it trips the breaker
immediately. *Can this be a double pole stat? *or am I just
misunderstanding the readings?

Curious symptom: *with the breaker off, I still read 1.12 VAC across
line, 2.66 from line to one load terminal, 1.48 to another. *It's a
radio shack DMM, and I've always assumed low voltage readings like
that were due to some kind of capacitative coupling, not real. *Maybe
not?

Anyway, heater sounds okay at 28 ohms, so it should be the thermostat
or the breaker. *But there would have to be a dead short in it to trip
the breaker immediately, shouldn't that show up on the resistance
readings?

Any more diagnostic suggestions? * What else to try? *I'm still
suspicious of the breaker, that's the only thing known to have
changed.

* * Quote: *"With the power on, I read 242 VAC across line, 0 across
* * load, 120 from each line terminal to load terminal"

120 from Line to Load may be the clue.

Difficult to be certain with a sensitive meter though.
Repeat that test using a 120V lamp in place of the meter.

If the test lamp lights, the heater element is shorted to
the sheath (or there is a wiring fault to Ground).

Jim- Hide quoted text -

- Show quoted text -

If I'm understanding this correctly, you suspect an actual heater
problem? Not inside the thermostat?

Does that make sense with the resistance reading on the element?

On Fri, 21 Nov 2008 16:48:36 -0800 (PST), TimR
wrote:


The heater is grounded. (shorted to ground)

Pull the cover to the junction box on the heater (one end or the
other) and disconnect both L1 and L2. Cap the wires with wirenuts.
Chech resistance from eack L terminal to ground. You should read
infinity. Then turn the stat on, with the heater disconnected. If the
fuse still blows it could be the stat. If you have continuity to
ground on the heater, it's the heater. Other possibility is a short to
ground in the cable from the stat to the heater. With powewr off,
check continuity from both L wires in turn to the neutral or bare
ground.
The baseboard heat in one of the bedrooms trips the breaker as soon as
I turn the thermostat on. We didn't know this until now because it
didn't get cold enough to need it until now.

But wait, there's more. The house (we just moved) had fuses until the
panel was replaced with a modern looking circuit breaker panel. We
tested that heater on inspection but that was while it was still on
fuses. I never thought to try it with the new panel.

The electrician says most likely bad thermostat, he'll come back and
look when he can schedule it, may be a while.

If so, I'd like to know what in a thermostat goes bad like that. I'm
not sure how they're wired inside.

I put a meter on the thermostat. The stat has four terminals, two
marked line and two marked load. With breaker off and stat off, I
read 28 ohms across load. That sounds reasonable, it should pull 8.6
amps if my math is correct, and the 20 A breaker should be fine.
Breaker off and stat on, 26.7 ohms appears across both load terminals
and line terminals, that sounds okay to me too, .8 and .7 ohms from
line to load across the contacts.

With the power on, I read 242 VAC across line, 0 across load, 120 from
each line terminal to load terminal, 120 from each line terminal to
ground. I didn't expect that. I thought a thermostat this old would
be single pole, and so one load terminal would read zero. That's with
the thermostat turned off, if I turn it on it trips the breaker
immediately. Can this be a double pole stat? or am I just
misunderstanding the readings?

Curious symptom: with the breaker off, I still read 1.12 VAC across
line, 2.66 from line to one load terminal, 1.48 to another. It's a
radio shack DMM, and I've always assumed low voltage readings like
that were due to some kind of capacitative coupling, not real. Maybe
not?

Anyway, heater sounds okay at 28 ohms, so it should be the thermostat
or the breaker. But there would have to be a dead short in it to trip
the breaker immediately, shouldn't that show up on the resistance
readings?

Any more diagnostic suggestions? What else to try? I'm still
suspicious of the breaker, that's the only thing known to have
changed.

On Fri, 21 Nov 2008 17:29:44 -0800 (PST), TimR
wrote:

On Nov 21, 8:02Â*pm, Speedy Jim wrote:
TimR wrote:
The baseboard heat in one of the bedrooms trips the breaker as soon as
I turn the thermostat on. Â*We didn't know this until now because it
didn't get cold enough to need it until now.

But wait, there's more. Â*The house (we just moved) had fuses until the
panel was replaced with a modern looking circuit breaker panel. Â*We
tested that heater on inspection but that was while it was still on
fuses. Â*I never thought to try it with the new panel.

The electrician says most likely bad thermostat, he'll come back and
look when he can schedule it, may be a while.

If so, I'd like to know what in a thermostat goes bad like that. Â*I'm
not sure how they're wired inside.

I put a meter on the thermostat. Â*The stat has four terminals, two
marked line and two marked load. Â*With breaker off and stat off, I
read 28 ohms across load. Â*That sounds reasonable, it should pull 8.6
amps if my math is correct, and the 20 A breaker should be fine.
Breaker off and stat on, 26.7 ohms appears across both load terminals
and line terminals, that sounds okay to me too, .8 and .7 ohms from
line to load across the contacts.

With the power on, I read 242 VAC across line, 0 across load, 120 from
each line terminal to load terminal, 120 from each line terminal to
ground. Â*I didn't expect that. Â*I thought a thermostat this old would
be single pole, and so one load terminal would read zero. Â*That's with
the thermostat turned off, if I turn it on it trips the breaker
immediately. Â*Can this be a double pole stat? Â*or am I just
misunderstanding the readings?

Curious symptom: Â*with the breaker off, I still read 1.12 VAC across
line, 2.66 from line to one load terminal, 1.48 to another. Â*It's a
radio shack DMM, and I've always assumed low voltage readings like
that were due to some kind of capacitative coupling, not real. Â*Maybe
not?

Anyway, heater sounds okay at 28 ohms, so it should be the thermostat
or the breaker. Â*But there would have to be a dead short in it to trip
the breaker immediately, shouldn't that show up on the resistance
readings?

Any more diagnostic suggestions? Â* What else to try? Â*I'm still
suspicious of the breaker, that's the only thing known to have
changed.

Â* Â* Quote: Â*"With the power on, I read 242 VAC across line, 0 across
Â* Â* load, 120 from each line terminal to load terminal"

120 from Line to Load may be the clue.

Difficult to be certain with a sensitive meter though.
Repeat that test using a 120V lamp in place of the meter.

If the test lamp lights, the heater element is shorted to
the sheath (or there is a wiring fault to Ground).

Jim- Hide quoted text -

- Show quoted text -

If I'm understanding this correctly, you suspect an actual heater
problem? Not inside the thermostat?

Does that make sense with the resistance reading on the element?


Yup - makes sense, and would be first thing to check,

As for the digital meter, just load it and it will be accurate.
Put a half watt 1 megohm resistor across the leads at the meter plugs.

In article , TimR wrote:
I put a meter on the thermostat. The stat has four terminals, two
marked line and two marked load. With breaker off and stat off, I
read 28 ohms across load. That sounds reasonable, it should pull 8.6
amps if my math is correct, and the 20 A breaker should be fine.
Breaker off and stat on, 26.7 ohms appears across both load terminals
and line terminals, that sounds okay to me too, .8 and .7 ohms from
line to load across the contacts.

With the power on, I read 242 VAC across line, 0 across load, 120 from
each line terminal to load terminal, 120 from each line terminal to
ground. I didn't expect that. I thought a thermostat this old would
be single pole, and so one load terminal would read zero. That's with
the thermostat turned off, if I turn it on it trips the breaker
immediately. Can this be a double pole stat? or am I just
misunderstanding the readings?

Have you checked the rating plate on the heater to make sure it really is a
240V heater? Sounds more to me like it's a 120V unit connected to a 240V
circuit, which of course would explain the instant breaker trip.

In article , Tony Hwang wrote:
Hi,
Be logical. If it worked with fuse OK and now breaker trips wouldn't it
mean the breaker is under rated? What is in there now?

Hi,
Be logical. Do the math. What is in there now is the 20A breaker he said was
in there. 240V / 28 ohms is less than 9 amps; how do you figure a 20A breaker
is under-rated for a 9-amp load?

In article , " wrote:

yeah DONT use digital meters for this sort of testing......

light bulb or analog meter

digitals too sensitive give capacitive coupled readings

Oh, fer cryin' out loud, haller, a digital meter is just fine for telling the
difference between 120V and 240V. The 1- and 2-volt readings that he got have
absolutely nothing to do with the breaker tripping.

On Nov 21, 9:04*pm, wrote:
On Fri, 21 Nov 2008 16:48:36 -0800 (PST), TimR
wrote:

The heater is grounded. (shorted to ground)

Pull the cover to the junction box on the heater (one end or the
other) and disconnect both L1 and L2. Cap the wires with wirenuts.
Chech resistance from eack L terminal to ground. You should read
infinity. Then turn the stat on, with the heater disconnected. If the
fuse still blows it could be the stat. If you have continuity to
ground on the heater, it's the heater. Other possibility is a short to
ground in the cable from the stat to the heater. With powewr off,
check continuity from both L wires in turn to the neutral or bare
ground.



The baseboard heat in one of the bedrooms trips the breaker as soon as
I turn the thermostat on. *We didn't know this until now because it
didn't get cold enough to need it until now.

But wait, there's more. *The house (we just moved) had fuses until the
panel was replaced with a modern looking circuit breaker panel. *We
tested that heater on inspection but that was while it was still on
fuses. *I never thought to try it with the new panel.

The electrician says most likely bad thermostat, he'll come back and
look when he can schedule it, may be a while.

If so, I'd like to know what in a thermostat goes bad like that. *I'm
not sure how they're wired inside.

I put a meter on the thermostat. *The stat has four terminals, two
marked line and two marked load. *With breaker off and stat off, I
read 28 ohms across load. *That sounds reasonable, it should pull 8.6
amps if my math is correct, and the 20 A breaker should be fine.
Breaker off and stat on, 26.7 ohms appears across both load terminals
and line terminals, that sounds okay to me too, .8 and .7 ohms from
line to load across the contacts.

With the power on, I read 242 VAC across line, 0 across load, 120 from
each line terminal to load terminal, 120 from each line terminal to
ground. *I didn't expect that. *I thought a thermostat this old would
be single pole, and so one load terminal would read zero. *That's with
the thermostat turned off, if I turn it on it trips the breaker
immediately. *Can this be a double pole stat? *or am I just
misunderstanding the readings?

Curious symptom: *with the breaker off, I still read 1.12 VAC across
line, 2.66 from line to one load terminal, 1.48 to another. *It's a
radio shack DMM, and I've always assumed low voltage readings like
that were due to some kind of capacitative coupling, not real. *Maybe
not?

Anyway, heater sounds okay at 28 ohms, so it should be the thermostat
or the breaker. *But there would have to be a dead short in it to trip
the breaker immediately, shouldn't that show up on the resistance
readings?

Any more diagnostic suggestions? * What else to try? *I'm still
suspicious of the breaker, that's the only thing known to have
changed.- Hide quoted text -

- Show quoted text -

Heater shorted to ground.

I can't check that. Well, I can't check that tonight, I've had
several beers while thinking about it, and I've got this rule about
mixing beer and 240 V. Wish I'd stuck to wine, but I really don't
like wine. humor

Anyway, thinking about it, your explanation makes perfect sense if the
thermostat is a double pole. Then we'd have 120 V from each hot leg
to ground, and heater is at ground.

I still have two logic problems with that. One is that I have trouble
believing a thermostat this old is a double pole. If it's a single
pole, it doesn't make as much sense. One hot leg ought to be
connected to ground all the time. So it should trip before the stat
makes, unless the short is on the other side of the heater. But in
that case I shouldn't get 120 V to both load terminals, I should just
get some kind of ratio. And if the short were in the middle of the
heater, I should have enough resistance in the circuit to avoid
tripping the breaker. Could be I just misunderstand how these things
are wired though.

The other problem is the timing - it worked a month ago, we replaced
the main panel, now it doesn't work........ oh, and I did check for
nail holes, but nothing has been hung in the room yet.

gotta have another beer and think about this some more.

thanks for the help, by the way. I take it your diagnosis is most
likely a heater problem, next likely short in the thermostat, least
likely bad breaker.

Doug Miller wrote:
In article , Tony Hwang wrote:
Hi,
Be logical. If it worked with fuse OK and now breaker trips wouldn't it
mean the breaker is under rated? What is in there now?

Hi,
Be logical. Do the math. What is in there now is the 20A breaker he said was
in there. 240V / 28 ohms is less than 9 amps; how do you figure a 20A breaker
is under-rated for a 9-amp load?



Hi,
Yup, be logical. If nothing changed and fuse is replaced with a breaker
which can feed 240V or 120V depending what type breaker is installed.

On Nov 21, 9:22*pm, (Doug Miller) wrote:


Have you checked the rating plate on the heater to make sure it really is a
240V heater? Sounds more to me like it's a 120V unit connected to a 240V
circuit, which of course would explain the instant breaker trip.

That's a reasonable guess, but I didn't supply all the information.
The house is from 1960 with no changes.

And I'm not sure that would have to trip the breaker immediately.
That would double the amps, but 8.6 doubled is only 17.2, within the
breaker rating and the 22 amp thermostat rating. I think it would
overheat and trip something in short order, but not instantly.

No, something either goes to ground or shorts hot to hot the instant
the stat makes.

Or something is wrong in the breaker panel. But it's not obvious to
me what that could be. Or why a fuse did not trip but a breaker
does.

TimR wrote:
The baseboard heat in one of the bedrooms trips the breaker as soon as
I turn the thermostat on. We didn't know this until now because it
didn't get cold enough to need it until now.

But wait, there's more. The house (we just moved) had fuses until the
panel was replaced with a modern looking circuit breaker panel. We
tested that heater on inspection but that was while it was still on
fuses. I never thought to try it with the new panel.

The electrician says most likely bad thermostat, he'll come back and
look when he can schedule it, may be a while.

If so, I'd like to know what in a thermostat goes bad like that. I'm
not sure how they're wired inside.

I put a meter on the thermostat. The stat has four terminals, two
marked line and two marked load. With breaker off and stat off, I
read 28 ohms across load. That sounds reasonable, it should pull 8.6
amps if my math is correct, and the 20 A breaker should be fine.
Breaker off and stat on, 26.7 ohms appears across both load terminals
and line terminals, that sounds okay to me too, .8 and .7 ohms from
line to load across the contacts.

With the power on, I read 242 VAC across line, 0 across load, 120 from
each line terminal to load terminal, 120 from each line terminal to
ground. I didn't expect that. I thought a thermostat this old would
be single pole, and so one load terminal would read zero. That's with
the thermostat turned off, if I turn it on it trips the breaker
immediately. Can this be a double pole stat? or am I just
misunderstanding the readings?


Assuming that it is really a 240V heater, then it sounds like the load
(heating element) is shorted to ground. What is the ohms reading from a
load terminal to ground with t-stat off? If you don't have a nearby
ground then use an extension cord to get a ground near the t-stat. The
fault could be either in the t-stat or at the heater or the wiring
in-between. Isolate the fault by removing the load wires then measure
again.

Note that you can't calculate the amp draw or wattage by using the
'cold' ohm readings of heating elements or light bulbs. The resistance
goes up as the element heats up.

Kevin


Curious symptom: with the breaker off, I still read 1.12 VAC across
line, 2.66 from line to one load terminal, 1.48 to another. It's a
radio shack DMM, and I've always assumed low voltage readings like
that were due to some kind of capacitative coupling, not real. Maybe
not?

Anyway, heater sounds okay at 28 ohms, so it should be the thermostat
or the breaker. But there would have to be a dead short in it to trip
the breaker immediately, shouldn't that show up on the resistance
readings?

Any more diagnostic suggestions? What else to try? I'm still
suspicious of the breaker, that's the only thing known to have
changed.

On Nov 21, 9:58*pm, Kevin Ricks wrote:


Note that you can't calculate the amp draw or wattage by using the
'cold' ohm readings of heating elements or light bulbs. The resistance
goes up as the element heats up.

Kevin

Blindingly obvious - and yet I never thought of it. Good point.

Seems like an ampmeter on the main panel would be a useful tool.
Wonder why there aren't any.

"TimR" wrote in message

The electrician says most likely bad thermostat, he'll come back and
look when he can schedule it, may be a while.

If so, I'd like to know what in a thermostat goes bad like that. I'm
not sure how they're wired inside.


Bypass the stat with jumper wires. If the breaker trips, it is not the stat.
If the heater heats properly, it may be the stat. A line voltage thermostat
is nothing buy a heat operated switch. While it may be bad, why not do the
simple diagnostic with a couple of short wires and wire nuts?

"TimR" wrote in message
...
The baseboard heat in one of the bedrooms trips the breaker as soon as
I turn the thermostat on. We didn't know this until now because it
didn't get cold enough to need it until now.

But wait, there's more. The house (we just moved) had fuses until the
panel was replaced with a modern looking circuit breaker panel. We
tested that heater on inspection but that was while it was still on
fuses. I never thought to try it with the new panel.

The electrician says most likely bad thermostat, he'll come back and
look when he can schedule it, may be a while.

If so, I'd like to know what in a thermostat goes bad like that. I'm
not sure how they're wired inside.

I put a meter on the thermostat. The stat has four terminals, two
marked line and two marked load. With breaker off and stat off, I
read 28 ohms across load. That sounds reasonable, it should pull 8.6
amps if my math is correct, and the 20 A breaker should be fine.
Breaker off and stat on, 26.7 ohms appears across both load terminals
and line terminals, that sounds okay to me too, .8 and .7 ohms from
line to load across the contacts.

With the power on, I read 242 VAC across line, 0 across load, 120 from
each line terminal to load terminal, 120 from each line terminal to
ground. I didn't expect that. I thought a thermostat this old would
be single pole, and so one load terminal would read zero. That's with
the thermostat turned off, if I turn it on it trips the breaker
immediately. Can this be a double pole stat? or am I just
misunderstanding the readings?

Curious symptom: with the breaker off, I still read 1.12 VAC across
line, 2.66 from line to one load terminal, 1.48 to another. It's a
radio shack DMM, and I've always assumed low voltage readings like
that were due to some kind of capacitative coupling, not real. Maybe
not?

Anyway, heater sounds okay at 28 ohms, so it should be the thermostat
or the breaker. But there would have to be a dead short in it to trip
the breaker immediately, shouldn't that show up on the resistance
readings?

Any more diagnostic suggestions? What else to try? I'm still
suspicious of the breaker, that's the only thing known to have
changed.



*I would go to the heater and disconnect the feed wires and cap them off.
Then go turn on the thermostat and circuit breaker and see what happens. If
the breaker doesn't trip replace the heater. If it still trips then go
remove the thermostat, connect the wires together and reconnect the heater
and see what happens. If the breaker still trips then you've got a problem
somewhere else on the circuit.

Aparently a lower rating than the fuse with the penny behind it? What's
really need is ammeter, to see what is the current draw. Also check the wire
size at the breaker. And wire type. If it's aluminum wire, that's a problem.
Different wire gage rated for different amperage of breakers. 10 gage, 30
amps. 12 gage, 20 amps. 14 gage, 15 amps.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Tony Hwang" wrote in message
...

Hi,
Be logical. If it worked with fuse OK and now breaker trips wouldn't it
mean the breaker is under rated? What is in there now?

Might want to read from the element to ground. Isolate both ends of the
element, and then read from element to ground. Should be OL (over limit) or
infinity resistance.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"TimR" wrote in message
...

If the test lamp lights, the heater element is shorted to
the sheath (or there is a wiring fault to Ground).

Jim- Hide quoted text -

- Show quoted text -

If I'm understanding this correctly, you suspect an actual heater
problem? Not inside the thermostat?

Does that make sense with the resistance reading on the element?

Resistance of filaments changes, when the temp goes up. Thus, the big
starting current. Can't calculate wattage like you can with smaller devices.

I'm thinking short to ground, or undersized breaker. Might also be wired
wrong.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Doug Miller" wrote in message
...


Hi,
Be logical. Do the math. What is in there now is the 20A breaker he said was
in there. 240V / 28 ohms is less than 9 amps; how do you figure a 20A
breaker
is under-rated for a 9-amp load?

For the same reason there is no pump on most sprinkler systems. For fire
protection in buildings. If there is a need, the fire department comes, and
brings a pump. In your case, you're the electrician, and you bring the
ammeter.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"TimR" wrote in message
...
On Nov 21, 9:58 pm, Kevin Ricks wrote:


Note that you can't calculate the amp draw or wattage by using the
'cold' ohm readings of heating elements or light bulbs. The resistance
goes up as the element heats up.

Kevin

Blindingly obvious - and yet I never thought of it. Good point.

Seems like an ampmeter on the main panel would be a useful tool.
Wonder why there aren't any.

Just went to a known good thermostat/heater combination in another
room, and took the same meter readings.

And got the same results. 240 across line, 0 across load, 120 from
each line to load terminal. Had the stat make, then 240 across line,
240 across load, 0 from line to load terminals.

What that tells me is the meter readings in the bad room are not
diagnostic of a grounded element because a good one reads the same,
but logically it seems a likely place to start.

Except for the fact that it worked fine before the panel was changed,
and doesn't work now. And going around the house i found two more
heaters that don't work, though they don't trip anything. Seems more
and more likely the installer did something wrong, but I'm not sure
what it would be. you don't touch the stat to change out the main
panel.

It's time to turn this over to a pro and see what he comes up with.

TimR wrote:
Just went to a known good thermostat/heater combination in another
room, and took the same meter readings.

And got the same results. 240 across line, 0 across load, 120 from
each line to load terminal. Had the stat make, then 240 across line,
240 across load, 0 from line to load terminals.

What that tells me is the meter readings in the bad room are not
diagnostic of a grounded element because a good one reads the same,
but logically it seems a likely place to start.

Except for the fact that it worked fine before the panel was changed,
and doesn't work now. And going around the house i found two more
heaters that don't work, though they don't trip anything. Seems more
and more likely the installer did something wrong, but I'm not sure
what it would be. you don't touch the stat to change out the main
panel.

It's time to turn this over to a pro and see what he comes up with.

Is there a pilot light either on the t-stat or wall heater?
If there is a 120V light, (or any other 120V device), on the load side
to neutral then that would make the meter read 120V between a hot
terminal and a load terminal when the t-stat switch is off.
I would still check for short to ground/neutral in the failing unit.
Ever find a label to tell brand model# and ratings?

Kevin

In article , TimR wrote:
On Nov 21, 9:22=A0pm, (Doug Miller) wrote:


Have you checked the rating plate on the heater to make sure it really is=
a
240V heater? Sounds more to me like it's a 120V unit connected to a 240V
circuit, which of course would explain the instant breaker trip.

That's a reasonable guess, but I didn't supply all the information.
The house is from 1960 with no changes.

Well, obviously there was one change, at least: from fuses to a breaker. And
it looks to me as though there's a decent chance that change was done
incorrectly.

And I'm not sure that would have to trip the breaker immediately.
That would double the amps, but 8.6 doubled is only 17.2, within the
breaker rating and the 22 amp thermostat rating. I think it would
overheat and trip something in short order, but not instantly.

No, something either goes to ground or shorts hot to hot the instant
the stat makes.

Exactly. Suppose you have, as I suggested, a 120V heater, not a 240V heater,
and the neutral is bonded to the ground in the heater -- not a particularly
far-fetched supposition for a heater original to a home built in 1960.

Then when a 240V supply is connected to that, one leg of the 240 goes to the
hot side of the heater, and the other leg to the (grounded) cold side. Wham!
Instant breaker trip.

Or something is wrong in the breaker panel. But it's not obvious to
me what that could be. Or why a fuse did not trip but a breaker
does.

HAVE YOU CHECKED THE RATING PLATE AS I SUGGESTED?

In article
, TimR
wrote:
The other problem is the timing - it worked a month ago, we replaced
the main panel, now it doesn't work.....

From here, it seems perfectly obvious that something was wired incorrectly at
the time the main panel was replaced -- like connecting a 240V circuit to a
120V device. CHECK THE RATING PLATE.

"TimR" wrote in message
...
Just went to a known good thermostat/heater combination in another
room, and took the same meter readings.

And got the same results. 240 across line, 0 across load, 120 from
each line to load terminal. Had the stat make, then 240 across line,
240 across load, 0 from line to load terminals.

What that tells me is the meter readings in the bad room are not
diagnostic of a grounded element because a good one reads the same,
but logically it seems a likely place to start.

Except for the fact that it worked fine before the panel was changed,
and doesn't work now. And going around the house i found two more
heaters that don't work, though they don't trip anything. Seems more
and more likely the installer did something wrong, but I'm not sure
what it would be. you don't touch the stat to change out the main
panel.

It's time to turn this over to a pro and see what he comes up with.

Are the 20A breakers you are talking about 2 pole 20's? Assuming 2 wire with
ground was the white wire accidently hooked up to be a neutral in stead of
the second hot? Just asking because we just wired up some 240v heaters with
12/2. Used 2 pole 20A breakers and marked the white as hot. I would think it
would have to be wires crossed some how in the new panel.

On Fri, 21 Nov 2008 19:07:50 -0800 (PST), TimR
wrote:

On Nov 21, 9:58Â*pm, Kevin Ricks wrote:


Note that you can't calculate the amp draw or wattage by using the
'cold' ohm readings of heating elements or light bulbs. The resistance
goes up as the element heats up.

Kevin

Blindingly obvious - and yet I never thought of it. Good point.

Seems like an ampmeter on the main panel would be a useful tool.
Wonder why there aren't any.

What you are forgetting, however, is the cold resistance will be the
lowest resistance and therefore the highest current. The Ohmeter will
give you "worst case".

On Sat, 22 Nov 2008 11:46:38 -0800 (PST), TimR
wrote:

Just went to a known good thermostat/heater combination in another
room, and took the same meter readings.

And got the same results. 240 across line, 0 across load, 120 from
each line to load terminal. Had the stat make, then 240 across line,
240 across load, 0 from line to load terminals.

What that tells me is the meter readings in the bad room are not
diagnostic of a grounded element because a good one reads the same,
but logically it seems a likely place to start.

Except for the fact that it worked fine before the panel was changed,
and doesn't work now. And going around the house i found two more
heaters that don't work, though they don't trip anything. Seems more
and more likely the installer did something wrong, but I'm not sure
what it would be. you don't touch the stat to change out the main
panel.

It's time to turn this over to a pro and see what he comes up with.


Was the panel installed by a qualified electrician?

If not, he likely mixed up some wiring, puttingboth sides of the
heater on the same side of the panelor something stupid like that.
Replacing a panel is a job for an expert, or at least someone who
understands how it is SUPPOSED to be done and is smart enough to
figure out how to make it work the way it is supposed to.

If not, he likely mixed up some wiring, puttingboth sides of the
heater on the same side of the panelor something stupid like that.
Replacing a panel is a job for an expert, or at least someone who
understands how it is SUPPOSED to be done and is smart enough to
figure out how to make it work the way it is supposed to.- Hide quoted text -

- Show quoted text -

I don't know how expert the guy was. But I got him back out to look
at his work.

He pulled the power wire off the heater, the breaker still tripped.
So not the heater.

Then he pulled the load wire off the thermostat. It no longer
tripped. So not the thermostat. So I have a short between the
thermostat and the heater, and it's going to be really difficult to
get to. But at least I know the next step.

In article , TimR wrote:

I don't know how expert the guy was. But I got him back out to look
at his work.

He pulled the power wire off the heater, the breaker still tripped.
So not the heater.

Then he pulled the load wire off the thermostat. It no longer
tripped. So not the thermostat. So I have a short between the
thermostat and the heater, and it's going to be really difficult to
get to. But at least I know the next step.

Uh-huh. Did you ever check the rating plate on the heater?

On Tue, 25 Nov 2008 23:05:10 GMT, (Doug Miller)
wrote:

In article , TimR wrote:

I don't know how expert the guy was. But I got him back out to look
at his work.

He pulled the power wire off the heater, the breaker still tripped.
So not the heater.

Then he pulled the load wire off the thermostat. It no longer
tripped. So not the thermostat. So I have a short between the
thermostat and the heater, and it's going to be really difficult to
get to. But at least I know the next step.

Uh-huh. Did you ever check the rating plate on the heater?
Not necessary. With the heater disconnected it still trips. Sounds
like a mail through the Romex somewhere.

Never let your mail man install heaters.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


wrote in message
...
Not necessary. With the heater disconnected it still trips. Sounds
like a mail through the Romex somewhere.

In article , wrote:
On Tue, 25 Nov 2008 23:05:10 GMT, (Doug Miller)
wrote:

In article
, TimR
wrote:

I don't know how expert the guy was. But I got him back out to look
at his work.

He pulled the power wire off the heater, the breaker still tripped.
So not the heater.

Then he pulled the load wire off the thermostat. It no longer
tripped. So not the thermostat. So I have a short between the
thermostat and the heater, and it's going to be really difficult to
get to. But at least I know the next step.

Uh-huh. Did you ever check the rating plate on the heater?
Not necessary. With the heater disconnected it still trips.

He doesn't have the heater disconnected yet. Not all the way. He says the
"electrician" pulled "the power wire" off the 'stat. But it's a 240V circuit.
There are *two* power wires. Only one of them is disconnected.

Sounds
like a mail through the Romex somewhere.

Or a 120V heater connected to a 240V circuit -- which a quick look at the
rating plate would confirm or disprove. Think about it: we already know
it's a 240V circuit. If the heater is 120V, and the neutral side of it is
bonded to the chassis -- entirely possible for original equipment in a home
built in 1960 -- then when *either* leg of the circuit is connected to the
heater, the breaker trips.

On Nov 25, 6:05*pm, (Doug Miller) wrote:

Uh-huh. Did you ever check the rating plate on the heater?

Well, no, I didn't. There's not one in an obvious location.

But do you realistically think this could be the problem?

These aren't plug in portable heaters. They are installed baseboard
heat, have been in place since the house was built c. 1960. They all
appear to be the identical make and model. I've put a meter on
several thermostats, ones that work and ones that don't. All have 240
volt power. All the thermostats are rated for 240.

Do they even make a 110 V model? I guess it's possible but I've
certainly never seen one.

In article , TimR wrote:
On Nov 25, 6:05=A0pm, (Doug Miller) wrote:

Uh-huh. Did you ever check the rating plate on the heater?

Well, no, I didn't. There's not one in an obvious location.

Keep checking until you find one.

But do you realistically think this could be the problem?

Yes, I do, as I've explained several times. If you have a 120V heater,
original to a home that's nearly 50 years old, it's entirely possible, maybe
even likely, that the neutral (cold) side of that heater is bonded to the
chassis -- a home that old is likely to have been wired with 2-conductor Romex
*without* a separate grounding conductor.

What do you suppose happens when a grounded 240V circuit is connected to
something like that?

In case it's not instantly clear, I'll explain.

One hot leg of the 240 is connected to the hot side of the heater. The other
hot leg is connected to the cold side -- where there's *supposed* to be a
neutral conductor, not another hot. The grounding conductor of the 240V
circuit is connected to the chassis of the heater. And that makes a dead short
to ground from the second hot leg.

These aren't plug in portable heaters. They are installed baseboard
heat, have been in place since the house was built c. 1960. They all
appear to be the identical make and model.

But, without finding the rating plate, you don't know, do you?

I've put a meter on
several thermostats, ones that work and ones that don't. All have 240
volt power. All the thermostats are rated for 240.

That would argue against this particular one being 120V, I admit, but it's
still possible. Maybe even possible that the same unit can be used as either
120 or 240, by changing the posistion of an internal jumper wire.

Do they even make a 110 V model? I guess it's possible but I've
certainly never seen one.

There are *many* 120V baseboard heaters.

Bottom line is that you need a competent, qualified electrician to look at
this and find out what's wrong -- and that description clearly does not
include either you or the guy you've had working on it. You need to get
somebody out there who knows what he's doing.

replying to Doug Miller, DIY guy wrote:
Didn't he say thermostat had two in, two out? 240 volt feed should have
thermostat to break current to both legs, similar to how double pull switch
works? 20A breaker is code for baseboard heater using 12/2ga in Minnesota I
believe. (I'm not electrician)

--
for full context, visit https://www.homeownershub.com/mainte...at-343471-.htm

On Tuesday, December 19, 2017 at 12:44:12 PM UTC-6, DIY guy wrote:
replying to Doug Miller, DIY guy wrote:
Didn't he say thermostat had two in, two out? 240 volt feed should have
thermostat to break current to both legs, similar to how double pull switch
works? 20A breaker is code for baseboard heater using 12/2ga in Minnesota I
believe. (I'm not electrician)
--


You're too late. The house burned down 9 years ago. O_o

[8~{} Uncle Flaming Monster