heat pump not starting all the time

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Old 02-21-15, 08:15 AM
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heat pump not starting all the time

I have a Rheem RPQL heat pump that is about 3 years old. So far this winter I have had lots of problems with it. It was icing up and the sensor and main board was replaced. Still iced up and some gas was added and it seemed Ok then.

Now at times the pump won’t start but the aux heat comes on. When this has happened I go out and check the codes and get L21 which seems to be a low pressure control and something about three times same thermostat call. I turn of the unit at the thermostat and open the breaker; wait about 5 minutes turn breaker back on and the set thermostat to heat. This seems to rest thing and it works for a while and then it happens again.

This has been happening when it has been very cold, with high temps in the teens and about 0 at night. But when I reset everything the pump does start and run sometimes with and sometimes without aux heat. I do notice that when I turn the heat back on after rest that the “heat on” indictor on the thermostat blinks for quite a while before the pump starts.

I am wondering if this is normal for the kinds of temps I’m having now or if something is wrong? I have a tech scheduled for Monday but would like to have any insight you might have before he comes.

Thanks in advance
 
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Old 02-21-15, 08:52 AM
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I'm not totally familiar with your unit but it can be a slightly low refrigerant charge issue as well as the extreme cold.

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Old 02-23-15, 04:59 PM
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update

As I mentioned in the first post i was having a tech come out today to look at the system. i canceled him because yesterday it was warmer, sort of normal for here this time of year, in the 40's and 30's a night. The heat pump ran normally coming on and satisfying the stat at 68 F without aux heat. It has gotten colder as the day went on today and is now about 20F and the pumps still seems to be working normally.

Is it possible that all this trouble was just due to the extreme cold? Can you get a L21 code when there is nothing wrong with the system. I suspect the gas level is Ok since it was just topped off two weeks ago which fixed the icing problem.

any feedback much appreciated.
 
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Old 02-24-15, 11:41 AM
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I suspect the gas level is Ok since it was just topped off two weeks ago which fixed the icing problem.
I can't comment on charging on the DIY board but I can tell you it is very difficult to correctly charge a heatpump system in the extreme cold.

If you read the bottom line of the piece I posted and it states the L21 code can happen in just the extreme cold.
 
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Old 02-25-15, 02:52 PM
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Pete,

thanks for the response. I had not read your initial post carefully enough. It got very cold again on Monday night, -7F, and the pump was not running just aux heat. I was hoping as it warmed up the pump would come out of the lock out on its own but it did not. On weds am temps near 40 the pump had still not started just aux heat. I rest by turning the breaker off and back on and the pump started and has been running normally all day. So it looks like it is normal for the pump to be locked out at extreme cold temps but should come out of it when it warms up. I have to reset to get it running again. Mine doesn't seem to be doing that so I have the tech back on cal for Friday.
 
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Old 02-27-15, 07:39 AM
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update to my last post

Today, Friday, the tech came out. The pump has been running noramlly since I last reset it, temp last night got down to about 20F. Tech said gas was fine, eveything else is fine. He showed me on the error list that there is an ** next to the L21 code.

** says somehting like unit will not rest unless low voltage is removed etc.

Tech said that means you have to reset it manually it will not come out of L21 on its own even when it warms up.

this seems crazy to me, many home owners would not know how to reset the pump and would have to call for service whenever the temp get in the 10-15F range.

can anyone comment on this? make and model of pump in my first post.
 
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