Thermostat Q

seedxpress · #1 Oct 18, 2006, 07:06 AM

I just installed a NOMA 7-day programmable thermostat for an electric furnace/AC system (ceiling unit). I believe the wiring (5-wire) is correct.

When I set it to COOL with Fan set to AUTO, it turns on the A/C and the fan automatically. Good.

But when I set it to HEAT with Fan set to AUTO, it turns on the heating system but the fan doesn't. The fan does turn on when I force it by setting the switch to ON.

Any idea why?

labman · Oct 18, 2006, 08:47 AM

The heating mode uses a different winding in the fan motor controlled by a different relay than cooling or fan on. The controls activate the relay a timed delay after getting a signal the gas is on. You could have a problem with the controls, most likely the relay, or the flame sensor, or the fan motor. Finding a point to check each component can be tough. Does your furnace give trouble codes by flashing a light?

seedxpress · Oct 20, 2006, 08:42 AM

I found out I had the wrong settings on my thermostat. I have to change setting HG (gas) to HE (electric) because the electric furnace will not turn on the fan automatically. The thermostat has to force it ON.

METT · Oct 29, 2006, 11:32 PM

HE setting is needed for electric furnace. HG is for gas furnace which will turn on the fan by itself.

sucosam · Nov 6, 2006, 02:54 PM

Changing this same setting also worked for me. The fan would not run unless I changed from Auto to On. But after making this change, mine also now works.



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