Heat Pump Relay Chatters

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  #1  
Old 01-19-06, 06:07 AM
T
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Heat Pump Relay Chatters

Ruud heat pump. Works fine in AC. Works fine in heat until heat goes below about 40 degrees. Then it starts a rapid changeover from heat to defrost mode. This happens about every second. I am afraid it is going to ruin the reversing valve or some other component. I looked inside the control box and it has an Essex type control 621-110. There is a change-oever relay and another relay mounted separately from the circuit board and there is also a bulb sensor mounted on the outdoor coil tubing. I feel certain that one of these controls is acting up but need to confirm which one.

Help appreciated to test or determine problem.

Thanks
 
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Old 01-23-06, 05:26 PM
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It sounds like it is going in and out of defrost rapidly. On most units the defrost is initiated by time and terminated by either time or temperature. With your control, it can be used for timed defrost OR temperature controlled defrost. I would suspect the defrost board if it is configured for timed defrost and the defrost thermostat if there is one. I'm not exactly sure if the thermostat you described would be the defrost thermostat or the balance point thermostat. You may have to do a little more checking to see where things are connected.

Ken
 
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Old 01-24-06, 10:21 AM
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The booklet on my unit does say that the board has a timer that operates on 30-60-90 minutes depending on the jumpers. At the end of the 90 minute timing period the timer sends 24V to the defrost relay through the defrost sensor for 10 minutes. It would seem that if the sensor (closes at 28 F and opens at 50-70F) were open the defrost cycle would never really begin and if the sensor were shorted, the cycle would end after 10 minutes. I think, in my limited knowledge, that the board must be causing this problem since the unit just continues to chatter for more than 10 minutes and the aux heat light on the thermostat comes on and off just as rapidly as the chatter. Would like your opinion on this. The rain has prohibited by getting to the outside unit for the past 2 days so will check some more when I can.

Thanks
 
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Old 01-24-06, 10:41 AM
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It is the board. If your unit has the board with the yellow wire on it, that you move to adjust the timer, right next to the test pins what you need is protech part #47-21776-06, or for a few dollars more you could get the kit that comes with the board and sensor. It's # is 47-21776-86.

Hope this helps.
 
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Old 01-24-06, 01:33 PM
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Smile

Shank
Thanks for the info. I will check this out. Sounds like you have it nailed.

Tony Cooper
 
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Old 12-16-13, 12:48 PM
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I know this thread is like 7 years old, but thanks to the power of the internet and searching I was able to find this post.

I have a 1.5 ton Ruud Heatpump that is doing the same thing as the OP. I had replaced the relay and was trying to figure out what was next.

I had mentioned the problem to my HVAC guy, even sent him a recording of what it was doing (at 245am) and he said he had never heard a Heatpump do that before.

After a little more research and stumbling to here, he agreed the defrost board is the most likely problem and I will replace it soon.

Thanks for the great help......even if it is 7 years old!
 
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