Fixing an Ice-Frozen Heat Pump / Air Conditioner
About a week ago, we awoke to a horrible grinding sound coming from our outside compressor unit for our heating system. We immediately turned our electric heat pump system to emergency heat (which powers down the outside compressor) and then went outside to discover this:
Our compressor was completely frozen over. We’d had a rainstorm overnight, and while the temperature outside was just above freezing, the fan chilled the air just enough that the rain froze to the unit and then built up overnight. The sound we heard was the fan blades chipping against the accumulated ice chunks on the inside of the unit.
I called Mike, our HVAC mechanic, and he recommended removing all the ice, then turning the unit back on for a minute to check for the noise. If the fan ran smoothly, all was well. If it continued to make the rattling sound, that meant that the blades had been bent by the ice, and we would have a somewhat costly repair on our hands. So I headed out into the rain with my hairdryer and a scraper and de-iced the unit.
I turned the system back on, prepared to cut it back off immediately if necessary. Fortunately for us, clearing the ice did the trick, and we had no further damage.
To be safe, I left the heat on the emergency setting until the rain stopped mid-day, so it would not freeze back over while we were out. And in the future we will pay more attention to freezing-rain forecasts. Running emergency heat over night may be an expensive proposition – but NOT as expensive as a compressor-parts replacement!
Getting Help with Your Heat Pump or Air Conditioner
If you’d like to get help with your heat pump or HVAC technician from a professional, we partner with ServiceMagic to help people find contractors in their area who can help. There’s a few short questions to diagnose your problem and then they match you up. Here’s the link (the service is 100% free for the consumer):
What do you think? Have you run across similar problems with this extra-cold winter?
Comments & Conversation on this Article...
18 Responses to Fixing an Ice-Frozen Heat Pump / Air Conditioner
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January 15th, 2009 10:09 am
I would call your HVAC guy back and ask him to figure out why the unit did not de-ice itself…they are supposed to “figure out” that there is icing conditions and cycle in such a way as to defrost themselves.
I’ve had heat pumps for years and although I’ve seen the beginnings of ice on mine on occasion, it always defrosted itself before the ice became a performance problem.
My opinion is that yours is not working right or it would not have reached that state.
Good luck!
CUAgain,
Daniel Meyer
January 15th, 2009 12:59 pm
Turn the lemon into lemonaide, I says. Now you have a valid reason to purchase a nice heat gun!
-Jon
January 15th, 2009 1:22 pm
I would call him out to find out why it didn’t go into a de-ice mode. That is suppose to keep the ice from building up. Our heat pump stopped de-icing a few years ago and they came out and replaced a circuit board, then all was well again.
January 15th, 2009 1:28 pm
Glad you posted this– we had the very same thing happen a few weeks ago. Our unit sits right where water runs off the roof and icicles were building up above the blades; I’m not sure the unit would recognize icy conditions since our coils were fine It was just icicles on the grate that protects the blade. Anyway, we did basically what you did and then hung a tarp from the roof to temporarily protect the unit from large quantities of water. I think in the spring we’ll build an extension of the roof that just barely covers the unit, but is high enough to allow sufficient airflow.
January 15th, 2009 1:51 pm
We installed a new heat pump/ac and gas furnace this past summer.
Our p/h guy said to switch to the furnace when outside temps got down to 20 degrees. Since we’ve been staying below 0 for quite a while now, the heat pump hasn’t been used.
I do see snow on the unit and wonder if it will damage it.
January 15th, 2009 2:20 pm
I have never had this particular problem, but I will tell you about a related problem that took forever for us to figure out: The pipe that drained condensation from the propane gas burner in our previous house would freeze up and eventually clog, causing our system to just stop working! Anyone who has a furnace that drains off condensation in that way needs to keep a close eye on it during super-cold weather.
Wrapping the drain line with insulating tape where it ran through unconditioned spaces helped, and if it was going to be super-cold for an extended amount of time we’d set up a simple work light to keep it warm enough to not freeze. But don’t do anything stupid like I did: Electric pipe tape is NOT compatible with plastic pipes!!! One of my more embarrassing Stupid Homeowner Tricks….
January 15th, 2009 11:20 pm
Hi all – Kim’s a little busy printing out more of our adoption paperwork, so I thought I’d throw in our comments….
@Dan – definitely true that in most normal situations the compressor will run in a defrost mode that will fix the problem. In this particular instance, we had gotten about 3 inches of rain in 32-33 deg. temperatures. The result was a flash-freezing effect as the rain trickled from our deck down onto the HVAC. I had some concerns about the defrost cycle not running properly but the HVAC guy said that in “the perfect storm” of weather, where rain hits the unit and freezes right away, this kind of icing can occur. I actually sat outside for about 30 minutes a few days later and listened – the unit is properly cycling to defrost mode periodically, so that satisfied me. If we experience the problem and further (e.g., when snows hit later this year), we’ll definitely have someone in to take a look.
@Carol – your HVAC guy is right. When the temperature gets too cold, the heat pump can actually pump colder air into your house, which will make your furance turn on in auxillary mode. Plus, additional air circulating in the house creates more heat loss. So, when its below 20 (or maybe 15 if you have a great unit), you should run indoor-only.
@Leslie – too funny about the heating wire – I can imagine that wouldn’t work. But we all make stupid homeowner mistakes … who cares – that’s what makes ownership so exciting
January 18th, 2009 8:08 pm
Freezing rain has always been a problem. Super cold air is coming out of the unit which is normal. Typically the air will be at least 20 degrees colder than outside air temperature. So you can see if it is near freezing and you get rain freezing on unit is going to occur. A simple way for the homeowner to rid the unit of ice is to shut the unit down and run water over the unit. Ice on grill and fan will melt quickly and you can resume normal operation. This makes short work of it. If freezing rain persists, and you don’t want to do this you can run system in emergency heat until freezing rain stops. Sometimes fan blades will ice up and cause out of balance, vibrations and noise will occur, the fan blades can break. Shut down and simply pour warm water over blades and return unit to service.
January 23rd, 2009 2:28 pm
I have been having a problem with my new heat pump all this winter and have lived at two previous houses in the same town that were heated with a heat pump and have never encountered the icing up that I have this year. My electric bill has tripled with this problem.
February 11th, 2009 2:01 pm
I just stumbled across this site while researching heat pumps. I have a heat pump in my cottage in Eastern Ontario. The installer put the fear of God into me about freezing rain and how it could stick to the fan blades causing them to go out of balance which in turn could ruin the unit. I switch to emergency heat when I am going to be away but that kind of deafeats the purpose of a heat pump. A friend of mine just had a heat pump installed and the installed looked at him sideways when he asked him about potential problems with freezing rain. Who is right?
February 11th, 2009 3:53 pm
Colin – having asked around a bit more, we’re pretty sure that this CAN happen when there’s a “perfect storm” (pardon the pun) of conditions – the air temp, the volume of rain (or if the unit is below an area where the water pools), the prior existing conditions.
We have had no problems with our unit since that day, and there WAS a tremendous amount of freezing rain falling, plus our unit sits under our deck, and the water was running directly onto it from the crack in the deck floor above. This winter has been an average of 10 degrees cooler than normal in our area, so that’s probably why we hadn’t run into the issue before.
Also, our HVAC guy is a friend, and he advised me over the phone – meaning he got paid nothing. It was certainly not to his advantage to make that up – for the friendship or for business. So we’re confident that the freezing rain was the problem.
If we find out otherwise, we will of course post an update, but so far what we’re finding is that this does happen – rarely. If it happens repeatedly, then there probably IS a problem with the de-icer, as a few people have mentioned above.
September 13th, 2009 7:15 pm
Just noticed this issue after not feeling any cool air in the house during heavy rain. Went outside and to my surprise the compressor? inside the outside unit under the fan was frozen over. The copper pipe coming from the compressor was also iced over and the ice was thick. I followed the white iced over pipe until it ended and went into the wall. I turned the unit off for the night and checked it again the next morning. All the ice was gone. The unit is currently working but what can i do to avoid this again? Was it the drizzling rain exponentially freezing as soon as it hit the pipe that caused this issue or am I running out of freon. I guess I’ll run it for 1 hour or so while it’s ccurrently not raining to see if the pipes start to freeze over again.
December 13th, 2009 5:47 pm
I ran into this problem today. I am so glad that I found this site. My heat pump was identical to the pic above. Thanks for the helpul info!!!
January 10th, 2010 10:36 am
What about putting a awning about 8 feet over the unit to keep most of the freezing rain out?
January 13th, 2010 11:46 am
Thanks for this timely information. We’re in Florida and it’s been uncustomarily freezing. Our unit is outside and has a big fence around it because of the HOA requirements to keep the area ‘good looking’. Our unit is frozen on the outside and a light coating on the inside. We’ve been lowering the temp in the house during the day and only using it at night. Everyone’s comments have been extremely helpful. Is there anything you can do if you don’t get full sun and can’t put in the de-ice wiring? My circuit board dies every 2 years (I was told they are very senstive) and the pipes are very close to the house so there isn’t alot to insulate.
February 6th, 2010 3:35 pm
While outside shoveling snow, I noticed that the heat pump sounded like it was struggling to run. I looked inside and saw a big chunk of ice the size of a soccer ball forzen on the compressor unit underneath the blades. The blades are not touching the ice. We recently put a metal roof on our house and we have had some huge snows in Virgina the past couple of months and the snow and ice is coming off the house down on the unit. How to you reccommend I correct this problem and would it be ok, for now, to pour hot water over the compressor to melt the ice that is there now. The heat pump was installed in 1996
February 6th, 2010 3:52 pm
Ronald,
It’s pretty cold out, so hot water could potentially freeze on an ice ball that size before it manages to melt it. Definitely turn the outside unit off, switch to your emergency heat for now (if you need it) inside, and see if you can get the ice to melt (a hair dryer would be better than hot water … can you borrow one?).
February 6th, 2010 6:45 pm
Ronald, Kim,
I do get the occasional ice build up on my blades when we have freezing rain here in Ottawa. You folks refer to it as sleet I believe. At any rate I have poured warm, not hot, water on the fan blades until the the ice melts and is completely gone. Sometimes one bucket does it but never more than three. The point is, it only has to be warm enough to melt the ice. It doesn’t have to come straight out of a boiling kettle. Water that is warm enough to comfortably leave your hand in is fine. Repeat until all the ice is gone. Since it’s water it will run away w/o freezing before you reach your objective. And yes, turn off your compressor and use only the emergency heating unit of your system. It may cost a couple of dollars more to run it that way but it will still be cheaper than having to replace your fan motor and blades.
Also, you might want to think about ice guards on your new metal roof to prevent the snow from sliding off onto your unit.
Colin