HVAC (gas) Question

[olds]

The pilot light won't stay lit on our furnace. I jumped the terminals for the thermocouple's lead wires but it still won't stay lit. I am assuming that the valve is shot, is this correct?

 

[Rubycon]

A thermocouple is a voltage producer not a switch. 🙂

You should read 30 mV off a good thermocouple that is HOT. Replace it otherwise.

 

[olds]

Hmmm.
I thought a thermocouple was made of two dis-similar metals. When heated, they expanded at different rates making contact and completing the circuit. Or is that 30 years ago?

 

[Rubycon]

That would be a thermostat.

A thermocouple is made of two dissimilar metals that will produce an EMF when heated on one side. The higher the temperature difference the greater the EMF produced. This is the Seebeck effect and is similar to a TE cooler in reverse.

 

[olds]

Originally posted by: C6FT7
That would be a thermostat.

A thermocouple is made of two dissimilar metals that will produce an EMF when heated on one side. The higher the temperature difference the greater the EMF produced. This is the Seebeck effect and is similar to a TE cooler in reverse.

Thanks
<--- runs off to find meter.

 

[Rastus]

Check your flue from the furnace to the roof. Sometimes, if a piece of it got knocked out of place, it can cause the wind to blow your pilot light out.

 

[Ronstang]

You can simply try a new thermocouple for a few bucks but don't be surprised if you gas valve is the culprit. In the last couple of years I have had to put a new gas valve on the hot water heater and on of the furnaces....after first trying thermocouples.

 

[skyking]

Originally posted by: Rastus
Check your flue from the furnace to the roof. Sometimes, if a piece of it got knocked out of place, it can cause the wind to blow your pilot light out.

That is some excellent advice for any gas user. Periodically check the flue path out, you can prevent all sorts of bad things from happening with some preventive maintenance.