Duo-Therm Furnace Issue

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Duo-Therm Furnace Issue

Postby GDufresne » Sat Dec 10, 2011 1:57 pm

Duo-Therm 900 series (90030-813) Gas Direct Vent Forced Air Furnace

Problem - the system works as it should when I turn the thermostat on with on/of switch. The fan starts, then the heat come on and the space heats up fine.

The problem is that once the space is heated, the heat will shut down but the fan continues indefinitely. It will not turn off and cycle again for a new heat cycle.

If I manually turn off at the thermostat, the fan will stop and I can get heat again by turning the unit on. I have left it on for several hours to see if the heat will turn on again, but the van just continues with no heat after the first "heat up" is finished.

What to do? Where to look?

Thanks in advance.

GARRY
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Re: Duo-Therm Furnace Issue

Postby Greg » Sat Dec 10, 2011 2:45 pm

Possibly the low temp. limit switch is bad. That should tell the fan that the unit has cooled down and turn the fan off.

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Re: Duo-Therm Furnace Issue

Postby GDufresne » Sat Dec 10, 2011 3:53 pm

Greg wrote:Possibly the low temp. limit switch is bad. That should tell the fan that the unit has cooled down and turn the fan off.

Greg


Would that prevent the gas from turning on again?

I didn't see that switch in the manual (for what it is), where would I find it.

Garry
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Re: Duo-Therm Furnace Issue

Postby Greg » Sat Dec 10, 2011 10:14 pm

It may be possible (I am not an expert on furnace issues) that if the low switch is shorted, the furnace "thinks" it is still running. When you shut it down manually at the thermostat you are tricking it into thinking it is starting up cold.

I am not sure where the switches on your furnace are located but they are usually flat,about an inch round and have 2 wires on them. there are 2, a high & low temp. switch I believe they are marked with the temp. setting on them.

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Re: Duo-Therm Furnace Issue

Postby GDufresne » Fri Dec 16, 2011 11:03 am

Hey Greg

Thanks for taking the time to answer my question. Checking your suggestion will have to wait until I'm ready to pull the unit out. Makes sense though.

For now, I'll just use it by turning the furnace off and on as needed.


GARRY

PS . . . love your signature line!! :lol:
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Re: Duo-Therm Furnace Issue

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