Duo Therm furnace 66000 series

madmedic · 08-12-2011, 11:50 AM

I have a 66000 duo therm furnace that works great until it stops calling for heat. When the burner shuts down, the pilot light also goes out. I then have to relight the pilot and it works great until it stops calling for heat again. Any help would be great.

**"007"** · 08-12-2011, 09:34 PM

Welcome madmetic to irv2.
In your burner there is a ceramic heat sensor that may have a carbon build up on it and has to be cleaned. The sensor is next to the igniter and the flame will heat the sensor to keep burner working until no more need for heat.
Just take some cleaner on cloth and wipe the sensor clean don't use anything abrasive or you could crack the ceramic.

SUMDALUS · 08-13-2011, 09:09 AM

madmedic,

The problem you are experiencing is probably one of the most frustrating when dealing with any pilot light - furnace or water heater.

A pilot light tends to go out when the burner goes out (reached set-point) for one primary reason -- the unmetered, low flow of LP to the pilot is not at it's designed flow rate and cannot sustain a flame.

Check where the pilot line attaches to the gas control valve and/or the pilot orifice. "Something" foreign may be restricting the flow. Here in Florida we have something people call "Gas Fleas" that get into the LP system. They look like little insects with wings (fleas) or possibly plant material.

Think in terms of a glogged gas filter on your car. Without pressure on the system, "something" does not affect the flow - it 'drifts/floats' out of the way. Once the system is fully pressurized (burner is lit - like stepping on the gas), "something" 'flows' towards the pilot line and/or orifice and accumulates enough to slow or block the normal flow.

Hope this helps.