Calling all heating and air conditioner guys.... I have a serious question....

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Forum topic by Rick Dennington posted 01-07-2010 09:42 PM 1236 views 0 times favorited 5 replies Add to Favorites Watch
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Rick Dennington

5909 posts in 3218 days

01-07-2010 09:42 PM

Greetings guys:

I have a serious question for anyone who can give me an answer.
The unit on the outside of my shop keeps freezing up , and iceing over. It started doing this a few days ago when the bad weather and snow hit. It has never did this before—ever. I keep the heat on about 67-68 inside, and it feels plenty warm in the shop. I can feel the warm air comeing through the registers. I shut the unit off, and took a look inside it. The condinser is clear of ice, but the smaller cylinder(the one that looks like a blowtourch size) is froze over. It has two lines coming out of it…one goes to the condinser, and the other goes up to the top somewhere. I think this is the freon tank.. tank and lines frozen over. All the black “fins” for air curculation(I think).......... frozen over. What’s going on, and what do I need to do? I’ve got the unit OFF now trying to get it to thaw out. But with 10 degrees outside now, don’t know if it’s gonna do anything.

Inquiring minds need to know, and all help appreciated…............I need to take care of it…. I need heat.. lol.

-- " At my age, happy hour is a crap and a nap".....

5 replies so far

View ajosephg's profile


1880 posts in 3584 days

#1 posted 01-07-2010 09:56 PM

Hi Rick
That’s a normal thing with heat pumps. I could go into a long dissertation on how they work if your interested, but don’t sweat it (pun intended). If it is working properly it will defrost automatically.

As a practical matter heat pumps don’t put out much warmth when the temp goes below 25 or so (depending on their age and whether or not they are a high efficiency unit). (The warm air you feel coming from the registers when it’s 10 outside is being supplied by the backup resistance heaters.) What I do when the temp gets cold enough that the heat pump runs continually is to manually switch the thermostat to emergency heat. The heat pump will then shut off and switch to electrical (resistance) heat and save some wear and tear on your compressor and outdoor fan.

-- Joe

View CharlieM1958's profile


16275 posts in 4242 days

#2 posted 01-07-2010 10:02 PM

Here is some info I found on another forum that might help:

I am familiar with your problem and I am gonna say you have one or maybe two possibility that will make your unit freeze when it gets cold outside. Textbooks will tell you that freezing starts to occur around the 40 degree F mark, but this is a general statement, as there are many factors that can contribute to this situation.
to get rid of this ice, most heat pumps have a time temperature defrost system. This system usually uses a timer; either a clock motor or an electronic timer. The timer will have a mechanical stops or electronic jumpers with times at 30,60, 90 etc. minutes dependant on the manufacturer. Some systems will use a pressure switch to detect that the coils have become stopped up with ice but this is not the norm on residential units.

There is some more info I will need from you, but I am going to assume the unit is not very old and give you a few sinarios until I hear back from you. First open up the panel on the side of your outside unit. I am asuming you are going to see a board inside, usually located toward the top. You should see a jumper, kinda like on on a hard drive that attaches two pins. you should see something like 30, 60, 90, and test written on the board. So you have this? Test is used to force the defrost mode. You should hear the reversing valve kick in and the fan should stop running. Does this happen? Ok, assuming all is working now comes the hard part. First of all I want to say your ac person is an idiot and you need a new one. Many people will say heat pumps are no good when the temp gets below 50 and to be frank with you that is bs. And to tell you to run your aux heat defeats the perpuse of having the heat pump. you will have to determine wheather you need the jumper on 30 60 or 90 etc. Obviously this is based on how cold it gets. the colder it is the sooner you want it to defrost so the setting would be the 30 and so on. Dont automatically assume 30 though as you want your unit to be as effecient as possible. if the test does not start the defrost cycle (give it a few minutes) then you have an issue with the board or the sensor that is on the board. However, (assuming the 24 volts in on the r terminal) if it does work but will not cycle defrost at specified times, It still could be the sensor but probably going to be an issue with the thermostat inside the unit usually attached to a loop on the copper of the coil. Make sure all power is of proir to accessing this. I have never been empressed with how these are mounted. they use a clip to hold the thermostat on the copper and sometimes are loose or have become looose or broken from previous ice build up.
This should be enough info to get you started. Please update me on your findings and we will go from there. Good luck.

-- Charlie M. "Woodworking - patience = firewood"

View Rick  Dennington's profile

Rick Dennington

5909 posts in 3218 days

#3 posted 01-07-2010 10:04 PM

Hi Joe: Hey, thanks a bunch for the reply and explanation on heat pumps. Before moving over here, I’ve never owned a heat pump. Always had gas. When I built the shop, they put in a brand new heat pump, and it’s only 7 years old. Narry a problem. But I’m glad to know about the ice build-up and freezing. I’ve really come to quite HATE a heat pump. To me, they ain’t worth two dead flys…. no worries.. gas is better… thanks again, Joe.

-- " At my age, happy hour is a crap and a nap".....

View Todd A. Clippinger's profile

Todd A. Clippinger

8901 posts in 4123 days

#4 posted 01-07-2010 10:15 PM

I’ve got gas!

Uhm, that is I’ve got a natural gas fired furnace in my shop and love it.

-- Todd A. Clippinger, Montana,

View ajosephg's profile


1880 posts in 3584 days

#5 posted 01-07-2010 10:22 PM

I have a dual fuel HP about 4 years old that uses propane instead of electricity for backup heat. If the house temp falls 2 degrees below the set temp. the propane furnace kicks on. That’s ok except that propane is outrageously expensive. (We can’t get natural gas where I live) Lucky for me the builder put in a woodburning fireplace insert that has its own set of ductwork that goes to every room in the house. So when it gets colder than about 30 I build a fire and let the old heat pump rest.

Following up on what Charlie said. If your outside unit is turning into a ball of ice, it may well not be defrosting properly. However, if you are having freezing rain like we did yesterday with the temp around 30 or so, they will get a lot of ice on them. (I’m pretty sure my unit has a pressure switch instead of a timer, but I’ve never opened it up to see.

-- Joe

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