Question about Ruud UBHC Air Conditioner
Brand new heat pump just installed all wiring is correct high voltage and low voltage but while its in cooling mode the back up heat is running. Why is the back up heat coil coming on while the heat pump is in cooling mode?
If back-up heat comes on when a/c is turned on and then the back up heat turns off shortly after the a/c turns off, then the low voltage wiring is NOT correct. Your "R" terminal is basically your "hot" and your "C" terminal is basically your "neutral" to simplify explanation. The Furnace supplies the "R" power to the thermostat and then depending on what wire the thermostat sends the power back on determines what the system does. The thermostat terminals are as follows "G" is fan, "W" or "aux" is elect heat, "Y" tells the outdoor unit to run, "O" or "B" tells the outdoor unit whether it is heating or cooling, and "E" is emergency heat. "G" should connect from the t-stat directly to the furnace and go no further. "W" or "aux" AND "E" should both connect to your "W" or "W1" terminal in the furnace, there should also be a "W" connection to the heat pump ( this allows the H/P to turn on the elect heat when the unit defrosts) "Y" and "O" or "B" may or may not connect to a terminal in the furnace, usually they just pass through the furnace from the t-stat to the H/P and get wire nutted in the furnace. Now, here is the key. As I mentioned previously "O" or "B", a system will only use one or the other. The entire industry (except for Rheem and Ruud) uses the "O" terminial which has 24v on it when you are cooling and no power when you are heating. Rheem and Ruud use the "B" terminal which is just backwards, 24v in heating and no power in cooling. this could also be your problem if the t-stat thinks it is telling the H/P to cool but the H/P is actuall interpreting the signal to heat. Check your amp draw on the furnace, if you have anything drawing 15 amps+ then it is most likely the actual elect heat running, if not then check the "B" terminal. Most universal t-stats come set from the factory to use the "O" terminal which is more common. Usually this can be changed in the installer setup menu on the stat or sometimes the stat will have separate "O" and "B" terminals
Posted on Jun 15, 2008
Check all of the factory wiring and compare to diagram. they do mess up at the factory
Posted on Jan 08, 2010
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Posted on Jan 02, 2017
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