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Old 10-31-2012, 08:12 PM   #1
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Heat pump not working properly after hurricane power outage


First post here on DIY, but after recently purchasing a home built in 1988, I am sure I will be on here more often.
The home came with a nice 16kW Generac generator and on Monday night before the power went out, we were experiencing some brownouts. The voltage was dipping pretty hard. It went out shortly after and the generator kicked in, but it does not power the heating system, so I don't think that affected it. When the power came back on today, I noticed that the Aux heat was running, which I expected because of the drastic temperature dip, but it has continued to cycle on/off to maintain temperature. I also have installed a TED5000 energy meter a few weeks ago, and I know when the heat pump used to operate before, the total house kW usage was around 8kW. Today I am seeing it operate around only 3.6kW and then after it fails to heat the home, it jumps to 17kW when the strip heaters kick in.
The inside circulation blower is functioning and the outside condenser fan is running, but am I safe to assume that the compressor is not running and I should check the contactor?
Thanks in advance.

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Last edited by phuz; 10-31-2012 at 08:14 PM.
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Old 10-31-2012, 08:25 PM   #2
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Heat pump not working properly after hurricane power outage


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Originally Posted by phuz View Post
First post here on DIY, but after recently purchasing a home built in 1988, I am sure I will be on here more often.
The home came with a nice 16kW Generac generator and on Monday night before the power went out, we were experiencing some brownouts. The voltage was dipping pretty hard. It went out shortly after and the generator kicked in, but it does not power the heating system, so I don't think that affected it. When the power came back on today, I noticed that the Aux heat was running, which I expected because of the drastic temperature dip, but it has continued to cycle on/off to maintain temperature. I also have installed a TED5000 energy meter a few weeks ago, and I know when the heat pump used to operate before, the total house kW usage was around 8kW. Today I am seeing it operate around only 3.6kW and then after it fails to heat the home, it jumps to 17kW when the strip heaters kick in.
The inside circulation blower is functioning and the outside condenser fan is running, but am I safe to assume that the compressor is not running and I should check the contactor?
Thanks in advance.
or call a contractor....

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Old 10-31-2012, 08:26 PM   #3
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Heat pump not working properly after hurricane power outage


yes see if contactor pulled in....
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Old 10-31-2012, 08:31 PM   #4
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Heat pump not working properly after hurricane power outage


Thanks. I had a circuit board,transformer, and contactor all go at my old townhouse from a surge but I figured the board was running since the fan and aux het came on. I'll check the contactor and control voltage tomorrow.
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Old 11-01-2012, 05:26 AM   #5
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Heat pump not working properly after hurricane power outage


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yes see if contactor pulled in....
The contactor is probably pulling in since the outdoor fan is running.

Could be the capacitor got weak on the compressor side.
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Old 11-01-2012, 06:56 AM   #6
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Heat pump not working properly after hurricane power outage


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The contactor is probably pulling in since the outdoor fan is running.

Could be the capacitor got weak on the compressor side.
Anyway to verify that without replacing it?
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Old 11-01-2012, 03:54 PM   #7
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Heat pump not working properly after hurricane power outage


With a meter that can read microfarads.

its a pretty cheap part to try.
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Old 11-01-2012, 08:58 PM   #8
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Heat pump not working properly after hurricane power outage


Well, I was wrong...it is NOT the compressor.
I pulled the panel off and both compressor and condenser fan are running.
After a few minutes, there is frost on the larger line coming from the compressor and it is obviously very cold.
The smaller line is hot and can be touched for a few seconds before needing to pull away.

A friends father works in HVAC so he gave a few things to try.
I turned on the A/C for a few minutes, then turned it off for 15 minutes, then turned the heat back on, in case the reversing valve was stuck or not properly seated.
When the A/C was on, the air coming out of the vents was cool, but definitely not cold. When I turned the heat back on, the air was luke warm again with just the heat pump running.
I measured a duct temperature on the first floor to be 81F. After a bit, the electric strips kicked in again, and within a minute the duct temperature was at 108F and slowly increasing.

He thinks something with either the expansion valve, reversing valve, or low refrigerant.
The unit is a Carrier 38YZA and refrigerant is R410A.

Not sure where to go from here.
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Old 11-01-2012, 09:23 PM   #9
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Heat pump not working properly after hurricane power outage


Need a the to check it.
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Old 11-01-2012, 09:34 PM   #10
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Heat pump not working properly after hurricane power outage


How cold was the room when you got that 81 deg. air? Heat pumps never put out a great amount of heat but they put out less when they are low on refrigerant. Only guages will tell you if that is the case. Your energy calculations are a bit confusing. A heat pump will use the same energy whether it's low on charge or not. Only when the resistance heat kicks in will it go up. It's time to pick up the phone and decide who is getting the check........
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Old 11-01-2012, 09:57 PM   #11
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Heat pump not working properly after hurricane power outage


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How cold was the room when you got that 81 deg. air? Heat pumps never put out a great amount of heat but they put out less when they are low on refrigerant. Only guages will tell you if that is the case. Your energy calculations are a bit confusing. A heat pump will use the same energy whether it's low on charge or not. Only when the resistance heat kicks in will it go up. It's time to pick up the phone and decide who is getting the check........
The room that was getting the 81F air was around 70F. I am not sure why the system would have lost refrigerant all of the sudden, but I am not convinced that is the problem. The energy monitor would show around 8kW anytime the heat pump was running prior to losing power on Monday. Now when the heat pump runs, it shows around 4kW and the house does not heat, so after a bit the electric strips kick in and it will jump to around 18-19kW. I know that a low refrigerant won't affect the current draw like that, but if one of the valves is failing to operate, would that prevent a load being put on the system, hence the reason I am only seeing half of the power consumption?
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Old 11-01-2012, 10:12 PM   #12
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Heat pump not working properly after hurricane power outage


Being low on charge does reducer current draw.
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Old 11-01-2012, 10:32 PM   #13
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Heat pump not working properly after hurricane power outage


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Being low on charge does reducer current draw.
...by 1/2?
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Old 11-02-2012, 05:52 AM   #14
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Heat pump not working properly after hurricane power outage


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...by 1/2?
That would depend on how low it is. The lower it is, the lower the amp draw since its not doing much work.


Until charge is checked. its all speculation.
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Old 11-02-2012, 07:08 AM   #15
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Heat pump not working properly after hurricane power outage


Thanks guys. I'm having it checked ASAP anyway, so we'll see.

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