Old AC unit


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Old 10-17-13, 07:28 AM
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Old AC unit

Quite recently our thermostat stopped working, and a little research led me to believe it is the transformer on our heat pump. It is a Ruud, and it is 19 years old. 10 years ago we installed a Carrier Gas furnace since then the heat pump has been used for AC only. Since the Ruud is so old we plan on replacing it as a part of a home improvement project next spring, and I am not crazy about installing parts that are not needed. So, can I disconnect the heat pump from the wall thermostat and just use it to control the furnace.

Thank you,
 
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Old 10-17-13, 09:45 AM
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If I understand correctly, your thermostat now controls both the Rudd and the Carrier. You can disconnect the Rudd - actually you basically do that when you switch the thermostat from cool to heat.
Normally your Carrier should have a transformer in it. If you were using the Rudd transformer, you will have to wire the thermostat to the Carrier transformer.

Make and model numbers for all three devices will help in sorting out what changes need to be made.
 
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Old 10-17-13, 11:36 AM
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Thank you, I will get that information tonight, and post it tomorrow.
 
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Old 10-18-13, 09:26 AM
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It is a Ruud Heat Pump Model # UPKA 030JAZ
a Carrier Gas Furmance Model # 58 MS A060 - 12
and a Carrier Thermostat that was installed with the furnace.

Thank you,
 
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Old 10-21-13, 10:29 AM
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This weekend I installed a Honeywell thermostat, with batteries to see if that would help. It did, but now the air handler fan won't stop blowing, the furnace will run wonderfully but the fan keeps churning even after the thermostat quits calling for heat. I have turned off the breaker to the AC unit, is there a way to disconnect the 24 volt to that and just run the Furnace.

Thank you,
 
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Old 10-21-13, 10:53 AM
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Is the thermostat set to "auto"? If it is set to "ON" it will run continuously.
 
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Old 10-21-13, 11:36 AM
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It is set to auto, and it works very well, except for the blower, which runs constantly. I think there is a problem in the low voltage portion of my ac unit and would like to be able to disconnect that entirely. We are replacing the unit next spring and don't want to put any more money that way.
 
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Old 10-21-13, 12:23 PM
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is there a way to disconnect the 24 volt to that and just run the Furnace.

If you want to remove the a/c compressor from the thermostat just remove the wire going to the "Y" terminal. You can also do the same at the furnace, if desired. If you only remove the "Y" wire at the thermostat make sure you tape off the bare end.

Check the low voltage wiring to make sure the bare wire going to the "G" terminal at the thermostat is not touching any other terminals. Do the same at the furnace making sure that bare wire end is not touching any others.
 
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Old 10-21-13, 12:39 PM
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I will do that tonight, thank you very much.
 
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Old 10-24-13, 08:42 AM
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I checked the wires going to G and they were complete. Also, when I unhook the wire at the G terminal on the circuit board at the furnace and turn on the power the fan still runs.

It seems to stop, or at least change significantly in volume, when the furnace kicks on. The furnace runs great, but as soon as the thermostat quits calling for heat it goes back to the constant, loud, fan.
 
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Old 10-24-13, 11:59 AM
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Sounds like the contacts in the fan relay on the control board are welded. You can try to "unweld" the contacts by tapping the relay with the handle of a screwdriver. It will be one of the black relays on the circuit board.
 
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Old 10-25-13, 11:19 AM
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Name:  Photo Oct 24, 4 53 02 PM.jpg
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Size:  35.6 KBHere is my circuit board. Which part would I be tapping?
 
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Old 10-25-13, 01:53 PM
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I believe it is to right of where all of the white wires attach to the board. There should be a single wire going to a terminal marked L1 and may be labeled BLWR.
Turn off power to the unit, locate the relay and tap on the relay. If you get lucky and it breaks loose it may operate for awhile. Odds are very great it will stick again. You will need to replace the board more than likely. I outlined the general area of the relay in white on your photo. Also, tap on the relay next to it. It is for the blower speed.
 
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