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Old 12-04-2015, 08:43 PM   #1
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Thermostat, Air Handler, and Compressor check


I rent my old place out and the tenant reported that the heat isn't working. The wiring seems a bit off but I know the heating was working about 1 year ago so I'm not sure what could have changed. I'll likely get a new T-stat but was interested in the opinions of some more intelligent wiring people.

The heat is electric so it does have a reversing valve. I mapped out the color of the wires and where they all go. The weird thing is there is a blue wire from the air handler that looks like it should be attached at the T-stat but it isn't even out of the wall like the other wires. Does something seem off to anyone here or do you think simply changing the T-stat will do the trick?

I did wire all the wires together at the thermostat (White, Yellow, Red, and Green) and turned it on and the A/C worked (it didn't work when I got there).
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Last edited by wyomble; 12-04-2015 at 08:50 PM.
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Old 12-04-2015, 09:15 PM   #2
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There isn't enough wires at the outdoor unit to work right.
If it did work and now suddenly doesn't, it's likely something else besides being midwired.

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Old 12-05-2015, 06:13 AM   #3
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- Your wiring diagram is either incomplete or your AH and compressor each have their own transformer. (you are showing no Common connection (C) ).
- If each has their own transformer then you SHOULD have two 24volt lines (R) at the Tstat (there should be 24V coming from R on the compressor when not connected to the AH)
- The top connection on the AH... is that "R"? (having trouble reading the writing)

- R on the compressor should not be connected to the Y on the Tstat. Y should connect to Y. It looks like it has been connected in reverse in order to deal with dual transformers?

- The blue *MAY* have been an old common connection at one time which is now being reused, but that's just a guess. Either way it looks to be a bit of a mess and more detail would be needed. Some actual pictures of the wiring block connections would help.
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Old 12-05-2015, 03:22 PM   #4
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The funny this is it was just the thermostat batteries. I had tried (2) new sets of batteries (one from a remote the tenant was using and one set out of a package she said she just bought). They were already low on juice. I brought a new thermostat and my own batteries and the new batteries worked.

It turns out the wiring is just super weird. Their is actually another yellow wire tied in with the red at the condenser which must run the compressor. The entire circuit board shuts down when the unit is not in use. Essentially, the 24V compressor line also runs the 24v power to the circuit board.
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Old 12-05-2015, 03:41 PM   #5
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Wyomble list the manufacturer and model numbers of the inside and outside unit, including the thermostat. You are sure that the thermostat is Heat Pump capable?

You can look up pictures of common wiring for thermostat to furnace/air handler to a/c or heat pump. Sometimes the heat pumps have a circuit board inside, that you only need a few wires to that controller, and the controller handles all of the work.

If you place the unit into aux heat and have the thermostat set up properly, it should kick on the heat strips.

Hang tight. One of the mod's that work in this area, should be along. It may not be until later today when they reply. update with the information at the top.

You can in the meantime take a look at the following on what each terminal means. http://www.behvac.com/troubleshooter41.htm
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Old 12-05-2015, 09:36 PM   #6
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Quote:
Originally Posted by wyomble View Post
The funny this is it was just the thermostat batteries.
If it's running on batteries then you don't need a common (c). It also won't really matter if the red and yellow are reversed. It will be a problem though if you ever decide to upgrade to a non battery thermostat.

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