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Heat Pump frosted up. What's going on, and should I be worried?
Posted by: clay
Date: December 27, 2018 12:28PM
Old heat pump. Outdoor unit is frosted up on the fins. Never done it in the 3 years we've lived here. Has been very wet here recently. Usually in 40's during the day, down into the 20s at night. Unit is still heating the house, though it seems to be running pretty much constantly, with some breaks during the day when it is sunny and the house is warmed a bit more with the sun. Yesterday afternoon I turned it off and hosed down the fins...melted all of the external frost, and was able to shoot the water inside and remove a bunch of that as well. It had started to frost up by evening and is now again completely frosted.

Something failing here? Weird weather situation? Old unit that needs to be replaced (I expect this is part of it, and we're planning for replacement. However, I'd like to delay as long as possible)?

I will post photos in a bit, but thought I'd get it going with this post to start. Need to leave for a bit, and will check back again later this afternoon.

Thanks!
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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: space-time
Date: December 27, 2018 01:40PM
when we were renting and I had a heat pump and it did that, my management company sent the repairman to defrost it. I don't recall if it did that again or not, but I do recall two things: electric bill was much higher that month, approximately $100-150 higher than usual. I think auxiliary heat kicked in a lot (this happens when heat pump cannot keep up). Then in Spring we learned the AC no longer worked, I don't recall exactly what as it was not my unit and we were moving very soon after that.


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Edited 1 time(s). Last edit at 12/27/2018 01:42PM by space-time.
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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: clay
Date: December 27, 2018 01:47PM
thanks, s-t. I had googled a bit yesterday and saw that link as well.
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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: clay
Date: December 27, 2018 01:49PM
pics:



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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: Speedy
Date: December 27, 2018 01:52PM
Green leaves on the ground in the first pic and you need heat?



Saint Cloud, Minnesota, where the weather is wonderful even when it isn't.
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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: clay
Date: December 27, 2018 02:09PM
Quote
Speedy
Green leaves on the ground in the first pic and you need heat?

yup :-) just the remnants of summer/fall. It will get cold enough that they will completely dry out. But for now they still look green.
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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: archipirata
Date: December 27, 2018 02:46PM
We had one that did that once and it was the fan motor that had failed. The compressor just kept running and since there wasn't enough air movement over the coils they just iced up until it was solid ice.



Athens, OH
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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: clay
Date: December 27, 2018 02:47PM
fan is still blowing as normal (at least to my eyes). I'm thinking it may be a defrost control board issue. Looking into ordering the part now. Under $50 for the part.
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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: Filliam H. Muffman
Date: December 27, 2018 03:05PM
Do you know the long term weather stats for your neighborhood? Have the low temps been that low on a regular basis every year you have lived there? If so, the unit needs service. Without doing more research on that specific model, (Edit: assuming the outside fan is operating properly) two issues that come to mind first are a low freon charge or a plugged orifice/expansion valve.



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Edited 1 time(s). Last edit at 12/27/2018 03:11PM by Filliam H. Muffman.
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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: Turboman
Date: December 27, 2018 03:07PM
Most likely low on refrigerant. This was the case on our unit.
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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: testcase
Date: December 27, 2018 03:34PM
I thought heat pumps lost effectiveness once the air temp hit ~ 40ºF. dunno smiley
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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: JoeH
Date: December 27, 2018 03:48PM
Quote
testcase
I thought heat pumps lost effectiveness once the air temp hit ~ 40ºF. dunno smiley

They get less effective at lower temps, but where they drop off depends on the design of a particular unit and installation. For installations in colder areas they can be set up to be effective down to 15-20ºF. That is enough to handle normal cold days, choice of auxiliary heat can be electric resistance, gas or other.



Edited 1 time(s). Last edit at 12/27/2018 03:52PM by JoeH.
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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: jh
Date: December 27, 2018 03:56PM
In our experience with our heat pumps they should be defrosting. As you suspect there is something amiss. Our previous heat pump froze over and was determined to not be defrosting properly. The age of the unit and the cost of the repair meant it was time to replace the unit. You need to check to see if it is kicking in aux. heat a lot and if so expect an increase in your electric bill.
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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: AllGold
Date: December 27, 2018 05:01PM
Although I know nothing about heat pumps and can't tell you what is wrong, even I know "that ain't right."



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Re: Heat Pump frosted up. What's going on, and should I be worried?
Posted by: TLB
Date: December 27, 2018 06:30PM
Just had the same Lennox unit with the same issue. Defroster valve or relay had failed. There is a test jumper on the board next to the contractor that will initiate defrosting if is the board, check the web for details. Mine was the valve which is deep in the unit. The repair cost was high and required evacuation of the refrigerant which I couldn't do myself. First stage heat did not work at all, so it was all emergency (resistive for me) heat and electric bill was elevated. My system was 25 years old, plus with the HCFC-22 ban in 2020, I opted for replacement.



Edited 1 time(s). Last edit at 12/27/2018 06:36PM by TLB.
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