My garage has a studio with electric baseboard heat in one room and an
electric wall heater in the entryway. It's expensive to run - something like
22 kW - so I mainly use that room in warm weather.
The entryway thermostat is an "Electromode Model M7-D double line break"
with a huge bimetallic strip. At random intervals, a kind of
screeching/hissing sound comes from it. (At least, I think that's where it
comes from. It never happens when I'm right near it.) I pulled the double
breaker than powers the baseboards, and turned the thermostat built into the
wall heater all the way down. So there shouldn't be any current flowing,
right? So where does the noise come from, and can I do anything about it w/o
Your info is a little sketchy. Does the wall thermostat control all the
heat? Is there only one breaker that feeds all the heat? The wall heater
most likely is not 22KW, but probably has a blower in it, which could squeal
on occasion. It's also possible that bad contacts in an electric heat line
voltage thermostat, could make a hissing sound when closing. If so, I'd have
Sorry about that. As far as I can tell, that thermostat only controls the
wall heater, which is a fan unit - probably 2 kW or so. The thermostats that
control the big baseboards don't seem to squeal.
I actually need to keep that wall system working in the winter to keep some
pipes from freezing, or I'd just disconnect it. If it might be the
thermostat contacts, I'll try cleaning them with a point file or emery
paper, or just replace the unit. BTW, the sound lasts about 3-5 seconds, and
sounds like sandpaper on metal.
That actually does sound like a bad thermostat. The bi-metal plate should
bend slowly, then quickly snap the contacts closed or open. If it doesn't
snap, but slowly closes its contacts, it'll hiss and spark at the point that
they begin to make contact
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