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#4596716 - 12/07/17 12:46 AM any hvac/heat pump experts here?
mikeinaustin Offline


Registered: 04/30/03
Posts: 350
Loc: austin, texas
i have a 7 year old carrier heat pump. tonight was the first night cold enough to turn heater on (about 40 outside). by chance, i happened to be near the outdoor unit when it came on. it turned on and fan spun for about 10 seconds then shut off for 5 seconds then back on, etc. i then turned thermostat way down and attempted to get it to output cold air instead of heat. this worked fine, the unit outside turned on and stayed on, no problems at all. i then retested heat mode and it once again started short cycling.

any ideas?

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#4596797 - 12/07/17 06:53 AM Re: any hvac/heat pump experts here? [Re: mikeinaustin]
Rolla07 Offline


Registered: 11/05/11
Posts: 4740
Loc: MTL, CANADA
I would try resetting the breaker and see if it somehow resets itself. As long as you set a temp indoors that is high enough (higher than indoor ambient air, it should work. Im not a hvac tech though.
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2007 Corolla Red Pearl 155k miles
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#4596804 - 12/07/17 07:03 AM Re: any hvac/heat pump experts here? [Re: mikeinaustin]
dnewton3 Offline



Registered: 05/14/07
Posts: 7392
Loc: Indianapolis, IN
It's hard to diagnose from several states away.

Which of the two motors was coming on and going off? Fan or compressor? Or both?

If the compressor is coming on and staying on, and only the fan is cycling, it could be a motor problem (thermal overload tripping in the motor itself).
It could be a system problem (pressure switch not sensing, or low refrigerant for the HP cycle).
It could be a host of other small things.

I realize that's not what you want to hear; makes it hard to DIY this problem. But it's not easy to troubleshoot without being there to poke and observe.
_________________________
The act of preventative maintenance, in and of itself, is FAR MORE important than brand/grade/base choices among lubes and filters.
- under maintaining something is akin to abuse/neglect; that can kill equipment by shortening the lifespan
- over maintaining something has never been proven to be anything but a waste of time and money

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#4596827 - 12/07/17 07:32 AM Re: any hvac/heat pump experts here? [Re: mikeinaustin]
Donald Offline


Registered: 03/21/04
Posts: 20469
Loc: Upstate NY
The electric booster coils are in the air handler inside the house. You need an HVAC guy with a schematic. The heat pumps are sophisticated units. There is also some defrost that happens. Maybe that's happening.
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#4596879 - 12/07/17 08:35 AM Re: any hvac/heat pump experts here? [Re: mikeinaustin]
mk378 Offline


Registered: 09/27/15
Posts: 1421
Loc: USA
In a defrost cycle, the compressor runs with the reversing valve in the cooling mode (to pump heat outside and thaw the outdoor coil) with the outside fan stopped. Also the electric heaters inside are turned on so cold air doesn't come from the vents in the house. This should only happen for a few minutes at a time then it will switch back to pumping heat inside.

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#4596934 - 12/07/17 09:12 AM Re: any hvac/heat pump experts here? [Re: mikeinaustin]
TTK Offline


Registered: 10/23/07
Posts: 566
Loc: TN
What he described is not the defrost cycle. A defrost cycle does not turn on and off like that. When it turns on it continues for the prescribed time( usually a few minutes) then reverses back to heating. May be a reversing valve issue.


Edited by TTK (12/07/17 09:14 AM)
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#4597176 - 12/07/17 02:02 PM Re: any hvac/heat pump experts here? [Re: mikeinaustin]
mikeinaustin Offline


Registered: 04/30/03
Posts: 350
Loc: austin, texas
just to close this thread. it was low on refrigerant. too low for heat cycle to work, but just high enough for cooling to work. cooling would have started to short cycled too as more refrigerant was lost over time.

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#4597453 - 12/07/17 07:27 PM Re: any hvac/heat pump experts here? [Re: mikeinaustin]
Nick1994 Online   content


Registered: 02/19/13
Posts: 10130
Loc: Phoenix, AZ
Originally Posted By: mikeinaustin
just to close this thread. it was low on refrigerant. too low for heat cycle to work, but just high enough for cooling to work. cooling would have started to short cycled too as more refrigerant was lost over time.
Where did the refrigerant go?

I too have a Carrier heat pump. 6 years old and A/C wasnít cooling that well this summer. Turns out the evaporator is leaking. 10 year warranty on parts so Iím working on that.
_________________________
2015 Hyundai Sonata 2.4L 79k PU 5w30 & OEM
2000 Toyota Camry 2.2L 228k M1 AFE 0w30 & Wix
1996 Jeep Cherokee 4.0L 146k M1 HM 10w40 & Fram Ultra

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#4597591 - 12/07/17 09:52 PM Re: any hvac/heat pump experts here? [Re: dnewton3]
dnewton3 Offline



Registered: 05/14/07
Posts: 7392
Loc: Indianapolis, IN
Originally Posted By: dnewton3
... or low refrigerant for the HP cycle).


Originally Posted By: mikeinaustin
just to close this thread. it was low on refrigerant. too low for heat cycle to work, but just high enough for cooling to work.


Well maybe I was a bit more accurate in diagnosis than I first imagined!

Glad it's working now.



Edited by dnewton3 (12/07/17 09:53 PM)
_________________________
The act of preventative maintenance, in and of itself, is FAR MORE important than brand/grade/base choices among lubes and filters.
- under maintaining something is akin to abuse/neglect; that can kill equipment by shortening the lifespan
- over maintaining something has never been proven to be anything but a waste of time and money

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