L21 code rheem heat pump


Old 03-07-15, 09:34 AM
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L21 code rheem heat pump

I have posted about this before but did not get any feedback on the last post so Iím posting a version of that again hoping for some feedback.

I have a Rheem RPQL heat pump that is about 3 years old. During a recent very cold spell the heat pump would not start and displayed an L21 code on the main board which is a low pressure lock out. The only way I could get the pump to start again was to rest by turning of the breaker in the house and turning it back on. I had to do this numerous times.

I had a tech come out and he showed me on the code list that there was an ** next to the L21 code. The ** says the unit will not restart until low voltage is removed. In other words it has to be reset manually.

I canít believe a unit would deigned this way, shouldnít there be a way that the unit would come out of the L21 code when it warmed up? Most homeowners would not be able to or want to trouble shoot this on their own and would have to call a tech every time it gets very cold.

It does appear that this is built into the design, I guess what Iím looking for is confirmation that this is true or an explanation of why it works this way and if all heat pumps work this way.

thanks in Advance
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Old 03-07-15, 09:54 AM
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You would want to investigate the cause of a tripping pressure switch.

Did your tech verify that the outdoor unit was clean, the outdoor fan motor run cap measured withing 10% of specs, the defrost control was operating correctly and the refrigerant level was okay?
Old 03-07-15, 12:38 PM
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That is what it's suppose to do. If you get one of the pressure switches open , you don't want it to run. Call a pro on this one.

Did the tech find the problem?

Last edited by skaggsje; 03-07-15 at 12:40 PM. Reason: added info
Old 03-09-15, 12:22 PM
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Thanks for the replies. The tech checked out all the things you mentioned, unit was clean , gas was just right etc. He said the L21 code was caused by the very cold weather, night readings 0 and below, we have had. I think this is true because when it is just normal cold, highs in the 30-40, lows upper teens low 20's. The unit works fine.
I had another reply by Pete to my previous post that implies that the L21 code would go away when the temp goes back up. My unit must be reset to get it working again. The tech said that is the way it is. I still find that hard to accept as I said before most people would do a service call for this rather than resetting it themselves. Tech told me it is fine to reset it the way I have been doing it by turning the breaker in the house off and back on.

I guess I'll just wait and see for now as the severe cold weather is over for the year I believe.
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