New thermostat. Compressor on, fan NOT!


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Old 09-14-13, 02:43 PM
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New thermostat. Compressor on, fan NOT!

Hi just bought a Honeywell RTHL 2501C thermostat to replace older liquid mercury non programmable. I have propane heating and electric cooling. Five wires, red, white, yellow, green. Old thermostat also had black and left that disconnected per instructions( the new one is battery operated does not need power)

But It is not working.

When "cool on" comes on, it turns on the compressor but not the fan! (I only let it run about 15" like that fearing it would damage the cooling unit). But if I turn the manual switch to fan-on then fan also comes on.

Looking at the wires directly, if I connect the red to green then fan comes on. If I connect red to yellow the ONLY compressor comes on (this unit is from early 90s).

Where is the logic that makes the fan come on when cooling is requested? Is it in the thermostat? In the central unit? Both?

If this type if thermostat relies on the unit downstream to turn on fan when cooling is requested then this type of thermostat will not work for me. Or is just this one thermostat bad?

Any advice appreciated.
 
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Old 09-14-13, 03:21 PM
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Aha! Figured it out. The switch in the back where you select "gas or oil" vs "electric or heat pump" was not switched all the way left to "gas or oil". It was almost all the way left, but not quite. I turned it all the way left and it works now. A little disconcerting since you could damage your compressor that way.

So keep in mind, if you have the same model.
 
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Old 09-14-13, 07:19 PM
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You know......answering your own questions is frowned upon here

When I started reading your first post.... that switch was the first thing I thought of. It's often overlooked when installing the new thermostat.
 
 

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