Honeywell thermostat operating backwards?


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Old 09-07-15, 11:18 AM
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Honeywell thermostat operating backwards?

Unusual problem with thermostat. Furnace is set to "Cool" and A/C only operates when wall thermostat is set to "Heat" . A/C will NOT operate w thermostat set on "Cool". Naturally the air temp is going down and will not affect shut-off since thermostat is calling for 'higher' temperature? Wheph!
 
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Old 09-07-15, 12:06 PM
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Is this a new thermostat install? Is this a heat pump? (reversing valve operating backwards).

You really do have to supply as much info as possible if anyone is to help you.
 
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Old 09-07-15, 12:09 PM
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Welcome to the forums.

That sound like you have a Coleman heating/AC system. With that system.... the thermostat always stays set on heat mode and you change from heat to A/C with a switch on the air handler.
 
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Old 09-07-15, 04:30 PM
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My Heat/Cool Thermostat operates the A/C only from demand heat position.

This is an Old Miller/Nordyne (1994) Heating and Cooling system with a Split System Single Phase Oudoor A/C 230v that is installed in a Mobile Home of the same vintage. The heating section went inoperative last winter and I tried some troubleshooting with no luck, after buying a few relays and replacing a burnt out xformer I caved and called a service tech.
After correcting some wrong installs by yours truly he got the heat running again. He wrote there was still a problem with the A/C signal coming from the wall thermostat but we left it at that.
Now I've replaced the Contactor that had a bad coil and bought a CT31 Honeywell Thermostat.
Here is the weird part. Nothing will happen with tstat in "Cool" position. The wall tstat only allows the A/C to turn on when it is in "heat demand". A/C works but won't shut off. Furnace is equipped with a "Cool/Off/Heat rocker switch which is in the Cool position.
Could this be some kind of Relay glitch? I'm bummed.
 

Last edited by Saltnpepa; 09-07-15 at 04:40 PM. Reason: Wiring Diagrams attached. It is Gas fired heat.
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Old 09-07-15, 05:15 PM
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Your picture didn't come thru.

The more information that you can give the greater chance that we can offer the assistance required to correct this problem.

This is the kind of job that is much easier when one is there.

I have switched over some old mobile home systems to a standard single thermostat control without the need for the heat / cool toggle at the furnace.
 
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Old 09-07-15, 05:15 PM
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We try to keep one topic in a single thread so I combined your two threads.

I replied previously in regards to your problem. With that type of furnace setup.... the stat stays in the heat mode at all times.
 
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Old 09-07-15, 05:40 PM
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Thank you PJMax. I now have both of your replies. Am new to forums so I will try to figure out how to stay with the program. For now there is manually controlled cooling, toughest at night, but I will be back tomorrow after I clear my head, lol. This Forum is much appreciated, though.
 
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Old 09-07-15, 08:12 PM
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The switch on the furnace is a manually set switch but the thermostat in heating mode will control the temperature based on what the stat is set for.

I know... it sort of defies logic. Normally when a stat is set to heat mode..... when the temperature drops the stat closes and you get heat. Which is how that stat works.

When the unit is in cool mode and the stat is heat mode..... when the temperature drops below the set temp....the stat closes to turn the A/C off. It's done inside the unit by a reversing control relay.

A competent tech could run a new cable to the stat with more conductors and change the operation of the relay. It requires rewiring the furnace to accomplish that.
 
 

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