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bobbya 12-12-2011 08:12 PM

Ruud defrost boards
I have a ruud heat pump condenser that keeps freezing up. The defrost board has been replaced 3 timesand it's a 2005 these systems have a reputation of this problem?

Done That 12-13-2011 07:37 AM

The odds that three boards were all bad is extremely low, so I suspect you have another problem. Are these the versions of controls with the coil and air temp sensors hard wired to them? Was the coil temp sensor placed back in the correct location?

bobbya 12-13-2011 08:05 AM

Yes they are hard wired into the board. The replacement board is different though,they have plugs on the board. I put the coil senser back where it was on the top right of the coils?

Done That 12-13-2011 08:13 AM

Yeah they switched to removeable sensors over the last few years. Charge, metering device problem, airflow, stuck reversing valve (rv), lots of things could be wrong....unless you know what you are doing I would suggest quit changing out parts and call a service tech....unless you are saying a tech did the first three replacements??

BTW those boards have a max defrost time of 14 minutes. Have you observed the unit when it goes into defrost to see how long it stays in that mode? Do the suction/liquid line temps change indicating that the rv is indeed shifting, or can you hear the "whoosh" sound of a shift?

bobbya 12-13-2011 12:17 PM

I am a tech,one of my co-workers went out and diagnosed it as a bad board,because it wasnt going into defrost mode(test cycle). Since everything was hardwired in I figured this would be a safe replacement. Usually these 3 things have been the problems that I have come across.This is the first time we have serviced this system.the home owner is the one that told us he has been having problems with it from the start. So im kinda stuck on it now,just seeing if there is anything else I could or should check before calling it a manufacturers defect?

bobbya 12-13-2011 01:09 PM

Sorry,I forgot to mention that the reversing valve is working, and when I installed the board the defrost cycle did work. Because it was warm that day I had to make it freeze by disconnecting the condenser fan. It did everything it was suposed to do. Now that I gave you the answers to the questions you asked, any thoughts?

Done That 12-13-2011 01:09 PM

OK, understand. All else I know it that Y and B must be present for test mode to work, but the test pins are ignored for the first 6 seconds after a power up. If you have Y and B and short the pins the short cycle delay is bypasssed and the rv should shift immediately, and keeping the pins shorted continouosly will make the unit remain in defrost until it terminates on time. On these demand defrost units they normally terminate on temperature which is selected by the on-board dipswitches. You might be able to slightly improve deforst performance by picking the highest temp, 80 degrees once you get it working right.

The Rheem district tech reps are pretty helpful if you can contact them for help??

Good luck.

bobbya 12-13-2011 01:22 PM

I really appreciate all your help

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