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HVAC Guru
HVAC Guru, HVAC TECH
Category: HVAC
Satisfied Customers: 14031
Experience:  15yrs in the HVAC industry with certificates and degrees.
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Amana pth operates in hoth cool and heat pump mode from

Customer Question

amana pth operates in hoth cool and heat pump mode from front panel and diagnostic run produces heat and cool ( not sure if in correct order - im not on site)
But with remote wired tstat it has to be shuttled between B and O valve sense to get the unit to function in heat/cool mode. Otherwise tstat only cools (or heats depending on active heat or active cool) regardless of whether tstat is calling for heat or cool. I have another identical unit having identical tstat connection that works as expected. Could the solenoid on the reversing valve have reversed polarity form the factory?
I have swapped out the control board and the tstat to no avail.
Submitted: 16 days ago.
Category: HVAC
Expert:  HVAC Guru replied 16 days ago.

Hello, one minute while I get some information together.

Expert:  HVAC Guru replied 16 days ago.

Hello and thanks for using this service! If you are a JA Member I would like to personally thank you and welcome you back! I am HVAC Guru an extremely experienced tech on the site and I try to get to as many customers as I can. NOTE it takes time for me to type research and add links so please wait for me to respond back I can only do this so fast. Secondly, I do not know your skill level so please try and let me know if I am going beyond your knowledge or comfort zone thanks! I strive for a 5 star rating from everyone especially our JA members.

Did you go into the installer menu on the thermostat and set it up for a heat pump with the correct setting for the crossover valve?

Customer: replied 16 days ago.
as I indicated I have an identical unit wired and configured the same that works as expected.
Expert:  HVAC Guru replied 16 days ago.

Then something would be wrong with the changeover valve have you tried switch the wires on the valve or at the thermostat?

Customer: replied 16 days ago.
no . I have tried all combinations of 'B' and 'O' on the tstat and the unit control board configuration . I get either heat operation regardless of tstat mode or cool mode regardless of tstat set to cool or heat.
Customer: replied 16 days ago.
Unit is heating now. But if the tstat is set to cool the unit continues to heat.
I can get the unit cool by changing either the tstat or unit to the opposite active reversal sense.
Expert:  HVAC Guru replied 16 days ago.

Do you have a separate O and B wire?

Customer: replied 16 days ago.
but if I do this it only cools regardless of whether tstat calls for heat or cooling
Expert:  HVAC Guru replied 16 days ago.

Do you have a two wires O and B or just one?

Customer: replied 16 days ago.
No. The configuration on thermostat is soft, as is the configuration on PTAC inself
Expert:  HVAC Guru replied 16 days ago.

Yes but on the thermostat do you just have an o/B terminal with one wire or two separate wires?

Customer: replied 16 days ago.
one wire
Expert:  HVAC Guru replied 16 days ago.

OK in the thermostat setting change the crossover valve to the other setting and try it.

Expert:  HVAC Guru replied 16 days ago.

Also do you have an O and B terminal on the thermostat or just an O/B terminal?

Customer: replied 16 days ago.
O/B on both ends
Expert:  HVAC Guru replied 16 days ago.

Can you reverse the wires to the valve?

Customer: replied 16 days ago.
I'm not on site. That is my question: is reversing polarity on the valve terminals inside the PTAC unit worth trying? I will be able to go onsite tomorrow and fiddle some more. I have to give the tenants notice.
Expert:  HVAC Guru replied 16 days ago.

Yes I would say reverse polarity is all you have left at this point, worth trying and it can correct that.

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Customer: replied 16 days ago.
I will try this tomorrow. From the schematic the rv solenoid is 230v. Is it possible that the line connections are the problem?
Expert:  HVAC Guru replied 16 days ago.

Yes very possible!

Customer: replied 16 days ago.
I'll check for a broken wire between the thermostat and reversing valve. That's the only thing making sense to me.
Reversing polarity on the solenoid would only matter if the core was magnetic.
Expert:  HVAC Guru replied 16 days ago.

Try it and see what happens