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Posted by JOHN F on December 28, 2006, 10:57 am
I have a forced hot air system and I have had to replace the limit switch 4
times in last 11 months. Part number HH 12zB and it has 200 degree rating.
All power feeds measure correctly. This is in town house with 3 floors of
ductwork. System works fine between limit switch replacements. I have
lined out limit switch for short durations ( middle of night and heat
needed), but I consider this a fire hazard over long term, plus unit runs
continually in that mode. With defective limit switch, fan runs
continuously when themostat calls for heat, but naturally the unit doesn't
actuate the pilot, so get cold air only.
Parts are fairly cheap..like less than $10, but more an irritation and
concern when traveling.
Thanks
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Posted by Eric in North TX on December 28, 2006, 11:29 am
First, I'm no HVAC tech, but I do maintain mine.
Just a thought;
I wonder what would happen if you put 2 in parallel.
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Posted by Tony Hwang on December 28, 2006, 11:58 am
Eric in North TX wrote:
> First, I'm no HVAC tech, but I do maintain mine.
> Just a thought;
> I wonder what would happen if you put 2 in parallel.
>
Hmmm,
Not a good idea.
They won't work in unison and defeat the purpose.
Can you increase blower speed?
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Posted by on December 28, 2006, 12:12 pm
"I have lined out limit switch for short durations ( middle of night
and heat
needed), but I consider this a fire hazard over long term, plus unit
runs
continually in that mode."
Can you use the fan switch in your thermostat instead of doing this?
And where are you getting $10 limit switches from? I thought they cost
more like $40?
Link?
I had a problem with mine once, and it turned out to be the crappy push
in terminals on the switch. Replacement models have both the crappy
push in terminals and regular screw terminals (like the back of an
electrical outlet).
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Posted by on December 28, 2006, 3:16 pm
>I had a problem with mine once, and it turned out to be the crappy push
>in terminals on the switch. Replacement models have both the crappy
>push in terminals and regular screw terminals (like the back of an
>electrical outlet).
I had the same problem or similar. The push in connectors were
different on the new switch compared to the original.The furnaces
wiring would go into the push in connector but didn't appear to be
very secure, so I soldered on larger gauge pigtails to the original
wiring. I then plugged the proper sized wire into the connectors.
I wonder if his connectors are arcing and failing?
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