furnace condensation freezing up

doglover3November 16, 2006

A non-profit club that I belong to has a furnace that has the condensation drain(clear plastic tubing) running through the wall and draining outside. We have usually only had a problem with the drain tube freezing up in extended and very cold periods(midwest winters). We installed a programmable thermostat this year and were told that we would have probably have more problems with the drain tube freezing up since the furnace probably wouldn't be running as much. We thought about putting in a condensate pump but have no floor drain or standpipe to run it to, which is why it drains outside in the first place. Someone suggested wrapping the drain tubing with some of that pipe wrap that has an electric current running through it to keep pipes from freezing, figuring that it would warm up the water enough that it should run freely. We could replace a portion of the tubing with pvc if that would work better with the pipe wrap. Looking for comments on how this would work or other ideas on how to solve this problem?

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Is this the condensate that is left over in the drain pan/pipe from when the AC was on in the summer? Something doesn't add up here - heating cycles don't usually produce condensation. Is this furnace in a cold attic? Or basement?

    Bookmark   November 16, 2006 at 9:35PM
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markiz37, where have you been for the past umpteen years? The newer heating units most certainly do produce condensate. Where do you think the term high efficiency condensing furnace comes from?
doglover, its never a good idea to put heat tape on any kind of plastic pipe. Does this pipe run horizontally where it exits the building? Maybe you can modify it to ternimate from a vertical position and your problems might be solved. Or maybe go from the plastic to copper inside the building then you can heat tape wrap the copper section outside.

    Bookmark   November 16, 2006 at 10:25PM
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Wow, I stand corrected. Live and learn.

    Bookmark   November 17, 2006 at 9:59AM
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This is condensation from the furnace that is freezing up. When the condensation freezes up in the tubing and blocks it, the furnace stops working. Unfortunately, the drain tube exits the building very close to the ground so there really isn't any room to make it go vertical and go with gravity. I like the idea of replacing at least some of the indoor section of the tubing with copper pipe, but I am not sure that we could actually make the copper pipe run outdoors and also have it wrapped with electrical tape. I am not sure how much copper pipe we would actually have to run to allow the tape to heat it up enough to keep it from freezing. Thanks for your input.

    Bookmark   November 17, 2006 at 10:20AM
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Can you drill a hole in the concrete floor and let the heating condensate drain into the stone under the slab? That wouldn't be that unusual. You could let the AC condensate continue to drain outside and connect a seperate tube/pipe from the furnace to the slab.

    Bookmark   November 17, 2006 at 1:46PM
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I love Rube Goldberg types of things. A bit wierd but they work.

If I had this situation and knew that I only had a problem during the coldes periods and wanted the furnace to run then, and, that the condensate backing up to the furnace was the cause of the shut down, I would:

Find an alternate route for the condensate should the outside tubing freeze. I might add a Y connect in the condensate line prior to it's exiting the wall. Maybe even near the furnace. Run a piece of tubing from the second outlet of the Y into a bucket or large container like a large cat liter pan. Even a five gallon bucket would work if the tubing was below the level of the tube exiting the furnace secondary heat exchanger (where the condensate comes from). That's what I would try and the wife would come down, take one look, shake her head and mumble something and exit, stage left.

    Bookmark   November 18, 2006 at 8:37AM
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deweymn, I think your wife and my wife took that "TREAT YOUR HUSBAND LIKE AN IDIOT" course together. LOL

    Bookmark   November 19, 2006 at 5:14PM
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Well, those are some pretty good ideas. I am not sure how much condensation actually comes out, I have never measured it. I might try it at home and see. Floor space is minimal as the closet where the furnace is also has shelving and cleaning supplies like buckets, mops, broom, vacumn. I had another idea to run by. The hose comes out of the outside wall near the ground so there isn't really a way to make any vertical turns. I thought that maybe if I could dig a small drainage hole, like with a bulb planter, down to below the frost line, cover the plastic tubing with some insulated foam pipe wrap and place the top of the hose inside the drainage hole I might be able to get it to drip down into the ground far enough that it won't get completely blocked with ice like it does when it is just laying on the ground. I could also cover the whole thing with something insulated and waterproof. If I am going to do this, I would need to do it quick before the ground freezes.

    Bookmark   November 20, 2006 at 9:04AM
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I may be missing something that will prevent your doing this, but here goes:

Install a condensate pump. Use the plastic line. Arrange the line so that it runs straight up, more or less, and then drops from there to the lowest point which is the opening outside. Make sure that the line is wide enough so that it will not air lock. Use as short an extension outside that you can and insulate it.

    Bookmark   November 20, 2006 at 7:05PM
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It sounds as if a condensate pump is needed. You will need to remove the check valve at the condensate pump. As the pump is emptied the water will be forced to the outdoors. When the pump shuts off the water in the line will return to the pump and not freeze at the exit of the building.

    Bookmark   November 21, 2006 at 11:35AM
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Our Heating & AC guy had suggested putting in a condensate pump in but we don't have a stand pipe or a floor drain to drain it in. They had said we could run pipe across walls to drain in the sink, but that would be ugly to look at, so I said no to that idea. He never suggested discharging it outside. I'll have to call them back up and see if that would work. Thanks for the suggestions. Now that I have read a little more about condensate pumps, we just might be able to do that. THANK YOU VERY MUCH!

    Bookmark   November 22, 2006 at 8:14PM
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I have the condensate pump and my line still freezes when it get really cold outside. It only sticks out about 6 inches outside my brick..It used to lay on ground..cutting it back to 6" helped but for some reason really cold nights it will freeze up..It is pointing vertically but just inside the wall (finished basement) it is horizontal.
I like the Y connector idea for backup

    Bookmark   December 9, 2006 at 9:48AM
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Yeah, the Y connector might work as backup, but you will need to point the backup end of the Y up (and maybe add an extra length of tubing vertically from the Y) to keep from filling your backup bucket with normal flow.

I also have a similar problem, except my furnace is in my well-insulated attic and has a condensate pump. Well, the pump line apparently froze up a couple of nights ago and cracked the tubing fitting, causing spray/leak inside my attic.

Removing the check valve in the pump as someone suggested previously might be the answer to my problem, as this will allow any extra water to drain back into the pump and not be as subject to freezing.

Any other ideas?

I think someone also asked the question of how much condensate a furnace will generate. I used a 5-gallon bucket as a backup the past couple of days, and my system generates about 1.5 gallons per day (nightime temp has been in the mid-teens, and daytime around 40-50 - thermostat kept on 68).

    Bookmark   December 9, 2006 at 7:30PM
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My condensing furnace drains about 3 gallons per day in colder weather . . . . assuming I cut it back to 57 degrees overnight - It would probably fill a 5 gallon bucket everyday otherwise

I know this because I put the furnace into service a week or two before I got all the drain plumbing done, and I had to empty the bucket down in the garage every day or it would overfill

I fashioned P traps (one for the furnace and another for the A/C) with removable plugs on both ends from 3/4 inch PVC and ran the condensate into the house septic system, just as all other water exiting the house does. Works just fine, with no danger of freezing . . . . or seeping under the foundation - I'll drain and clean the P traps once per season and pour a little bleach into the one not being used for the season


    Bookmark   December 9, 2006 at 10:29PM
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How do I remove the check valve in the pump?
My furnace just froze up again last night..I was out with hot water de-icing the line. I haven't done the Y connector idea because I'm afraid of forgetting about the bucket filling up. How do I remove the check valve in the pump? What is a check valve? It would be great if the water was removed from the line after dispensing and worked it's way back to the pump. Believe it or not I just put antifreeze in the reservoir of the pump for a temporary fix. Eventually, I suppose, it will all get pumped out. Also, may try to drain this line out my regular drain lines (via tapping into a bathroom drain) Would this be a HVAC service call or a plumber?

    Bookmark   January 29, 2007 at 3:26PM
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My hardware store manager has recomended that I run heat tape that is insulated with steel braid thru the indside of the PVC pipe to keep it thawed. My only concern on this is the device stated "do not submurge in water" on the attached information. Anyone have experience with this suggestion?

    Bookmark   December 23, 2010 at 9:53AM
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I am having smae problem, installer stated it would not freeze but it has now twice this winter, with extended days of sub 10 degree weatehr. I have resorted to using a turkey baster to empty the pump so the heater is still running. I am considering sometime of mainfold system to turn off the line up into the attic to the outside and bypass that line to a five gallon bucket that could be used during the 10 degree below days. My furnace produces enough condensation in 2 hours to fill the pump. The pump will then run continously trying to pump but won't empty. Thus the use of a turkey baster to empty the pump and then the heater kicks back on. There has got to be some easier method to solve this problem.

In searching for answers on another board an HVAC suggested getting a heat tape made for DRAIN LINES ( not regular heat tape and wrapping the the drain line to keep it from freezing.

    Bookmark   February 5, 2011 at 11:16PM
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I have this same problem. my plumber is going to install a water heating cable to keep drain pipe from freezing.

    Bookmark   February 27, 2015 at 12:29PM
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Also until heating cable gets here, plumber told me to put a little anti freezer in pipe and cup thst initially holds water coming out and that helps lots. When it's gotten very cold I ran a small space heater next to the place where water comes out. Works like a charm but I'm not comfortable leaving heater on for a long time.

    Bookmark   February 27, 2015 at 12:32PM
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Gee, we are getting responses to a post that is about 6 years old.

A couple of things to keep in mind. Fluid from a condensing furnace is very acidic. It will probably chew through copper pipes very quickly if not neutralized before it enters them. Likewise, you don't want it irrigating your slab. There is simple equipment to do this with percolation through limestone chips or similar material.

The condensate from a furnace comes from the combustion chamber. Be careful if you mess with this. If you do something ignorant, you might get combustion gas released where it is not supposed to be.

    Bookmark   February 27, 2015 at 5:04PM
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