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Author Topic: Need Help a/c blowing hot air  (Read 2283 times)

Offline ddavis263

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Need Help a/c blowing hot air
« on: July 22, 2010, 04:54:57 AM »
No good deed goes unpunished.  My neighbor asked me to install her new programmabel t-stat.  Well after much trial and tribulation(and blowing of hot air) we noticed that the one she bought is not compatible with heat pump systems.  So we put the original back on and guess what...it is still blowing hot air. 

What did i do?  and how do i reverse it?
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Offline Repair-man

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Re: Need Help a/c blowing hot air
« Reply #1 on: July 22, 2010, 05:49:39 AM »
It is possible that you burned out the board at the outside unit, causing it to run in the heat mode. There is a reversing valve on all heat pumps which is pre-set to run on Heat until it is activated by the thermostat circuit. Unfortunately, there are solid state control boards on these units that do not toloerate being wired up wrong (wrong t'stat will do the same)

Now it's time to  have a real A/C person come trace down the problem. There are several more wires and things involved with heat pumps that do not correspond with a simple A/C system.
« Last Edit: July 22, 2010, 05:51:38 AM by Repair-man »
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Offline ddavis263

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Re: Need Help a/c blowing hot air
« Reply #2 on: July 22, 2010, 07:23:44 PM »
FYI the red wire goes to the RC terminal NOT the RH terminal like the directions clearly state.
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Offline JWWebster

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Re: Need Help a/c blowing hot air
« Reply #3 on: July 23, 2010, 08:48:29 AM »
A heat pump has to have extra terminals for the reversing valve and defrost functions. Emergency heat and all that. A regular thermostat won't "cut it"
 It is best to get the thermostat recommended by the manufacturer and have a qualified tech connect it up like Jimbo said. You might have it working now but when that heat switch gets thrown something is gonna get fried. Then the tech gotta TRY and straighten out the mess.
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Offline jumptrout51

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Re: Need Help a/c blowing hot air
« Reply #4 on: July 23, 2010, 05:41:35 PM »
Also,if it is the correct thermostat,there is a factory jumper wire from RC to RH.
For a heat pump to operate they both have to be energized.
If you have a 2 transformer system you remove the jumper and wire in one transformer to RC and the other transformer to RH.
Just make sure the correct transformer goes to the correct terminal.

That is,if you have a heat pump thermostat that will have the O and C terminals.
Unless of course,you have a Lennox system that is color coded and terminal coded on the secret Lennox system.
« Last Edit: July 23, 2010, 05:46:59 PM by jumptrout51 »
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