Air conditioner problem

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It is me with problem with the upstairs heat pump again. When the compressor comes on, the fan on the compressor starts. Usually within a few seconds, the fan motor shuts off but the compressor keeps running. Before the fan can completely spin down, the fan motor comes on again. It often keeps repeating this, so it is only blowing out the hot air about half the time the compressor is running. I think this must hurt efficiency. What could be the problem?
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On Thu, 21 Apr 2011 16:42:32 -0400, Jan Philips wrote:

Has it always done this? Does it coincide with the outdoor temperature? Also the fan doesn't need to force air through the condenser at certain temperatures say below 50F
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The title says AC problem, the body talks about heat pump. Which is it doing when the problem is ocurring, heating or cooling. If it's doing this in cooling mode, I'd say it's almost certainly a bad fan or the wiring going to the fan. Not sure how the fan is used in heating mode.
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Or possibly a high or low limit switch. I'm confused also on whether or not he is heating or cooling.
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On Thu, 21 Apr 2011 18:53:05 -0400, "Ed Pawlowski"

I've only noticed it when cooling, but this unit goes to the upstairs, so it doesn't get used much as a heater.
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On Thu, 21 Apr 2011 15:29:01 -0700 (PDT), " snipped-for-privacy@optonline.net"

It is a heat pump in A/C mode. I had a lot of problems with this unit about 2 years ago and they replaced the fan motor twice, the capacitor, and the thermostat. It doesn't act like a loose connection because the on/off times seem consistent.
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On Thu, 21 Apr 2011 21:41:28 +0000 (UTC), "A. Baum"
I am pretty sure it has not (but I can't be certain).

It is hard to tell since we haven't had any really hot weather yet. Highs have been mid 80s to low 90s.

This is when it is at least mid 80s.
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wrote:

I would think if it's in the mid 80s and in cooling mode the condenser fan should be running 100% of the time the compressor is on. A circuit diagram that shows how the fan is powered would be the place to start, or you could just follow the wires and/or put a voltmeter on the fan and see if it's the power to the fan or the fan that's the issue.
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On Thu, 21 Apr 2011 16:25:09 -0700 (PDT), " snipped-for-privacy@optonline.net"

That is beyond what I can do. I probably need to have a qualified A/C repairman check it.
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On Thu, 21 Apr 2011 19:16:21 -0400, Jan Philips wrote:

I'd say then and others might agree there might be a problem with the fan/ fan control especially if the indoor temp is considerably higher than the thermostat setting. In this scenario the demand for cooling would still be high and I see no reason for condenser fan cycling on/off unless the motor has a built in thermal shutoff that is acting up. Also if the fan isn't pulling enough heat out of the refrigerant it's not going to condense enough back into liquid and your cooling will suffer. I'd get someone to have a look that services that make of unit.
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On 4/21/2011 4:42 PM, Jan Philips wrote:

Could be a 2 speed fan with only the high speed working.
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Great thought. IF the OP could contact the mfgr and get a wiring diagram and post it, we could probably settle things quickly, but right now everyone is shooting in the dark.
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On Thu, 21 Apr 2011 18:56:56 -0700 (PDT), "hr(bob) snipped-for-privacy@att.net"

It is a Rheem RPKA-031JAZ. I googled and couldn't find the info. I went to the Rheem website and searched there, didn't find it. I emailed Rheem, but they don't seem to have it.
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On 4/21/2011 3:42 PM, Jan Philips wrote:

Most heat pumps are setup to cycle the condenser fan motor which will cut on and off during moderate to cold outdoor temperatures. I include a condenser fan cycling control on all standard AC units I install for restaurants because the AC is usually run year round and the pressure in the liquid line from the condenser needs to be kept high enough for the AC to operate properly. Some conventional straight AC condensing units have a two speed condenser fan motor and the control may actually cycle the fan on and off if it's cold enough outdoors. You can spend even more money and get a heat pump that has variable speed compressor and fan motors. :-)
TDD
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On Thu, 21 Apr 2011 22:41:41 -0500, The Daring Dufas

I need to time it, but I estimate that it is on for 10 seconds, off for 10 seconds, etc. Would it cycle that quickly? And it is about 85F outside.
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On 4/21/2011 11:41 PM, Jan Philips wrote:

If it's a pressure control, the rapid cycling at that temperature could indicate a low refrigerant charge. Model number and information on operation including diagram may show a pressure switch.
TDD
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On Fri, 22 Apr 2011 00:12:57 -0500, The Daring Dufas

It is a Rheem RPKA-031JAZ. I searched for more info but didn't find it.
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wrote:

She made it clear a while back that it's cooling mode that she's concerned about. And the very first post indicated that the compressor stays on, while the FAN shuts off. That is most certainly NOT a low refrigerant problem.
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On 4/22/2011 9:46 AM, snipped-for-privacy@optonline.net wrote:

Do you know anything about condenser fan cycling controls that operate on what's commonly called head pressure? Look it up, try to understand it then get back to someone like me who has about four decades experience with refrigeration and HVAC equipment. Search "head pressure" and "condenser fan cycling controls". If you have a problem understanding it, I can explain it without calling you names or questioning your parentage or brain power. ^_^
TDD
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wrote:

I never questioned your parentage or brain power. I do question your ability to read and follow a thread or provide usefull answers. Within a few posts, the OP stated that what she is talking about occurs during COOLING. Yet you come along posting:
"Most heat pumps are setup to cycle the condenser fan motor which will cut on and off during moderate to cold outdoor temperatures."
She said it's mid 80's outside, so what does that have to do with Jan's question?
" I include a condenser fan cycling control on all standard AC units I install for restaurants because the AC is usually run year round and the pressure in the liquid line from the condenser needs to be kept high enough for the AC to operate properly."
Which has what to do with Jan's question?
" Some conventional straight AC condensing units have a two speed condenser fan motor and the control may actually cycle the fan on and off if it's cold enough outdoors. You can spend even more money and get a heat pump that has variable speed compressor and fan motors. :-) "
Which has what to do with Jan's question?
Since you have 40 years experience, presumably you can pull up a schematic for this heat pump. If you can show us where it has a fan control that relies on cycling the fan based on refrigerant pressure in cooling mode, I'll conceed your point. Until then, I doubt it does.
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