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Furnace - High Efficiency Furnace Exhaust Pipe Ices during Winter

wp2's picture

We had a high efficiency furnace installed about 10 years ago, which was installed with a PVC exhaust pipe vented from the side of the house, approximately 3 feet above ground.

Each winter water/condensate drips from the exhaust pipe and forms an ice pillar/stalagmite which I fear could clog the exhaust pipe and cause the furnace to shut off.

Because this is a summer home in northern Michigan, our neighbor was kind enough, in past years, to check the pipe periodically and knock the ice pillar down when needed. However, our neighbor has moved (victim of the recession) and we no longer have a neighbor who can check the pipe in winter.

Does anyone have an idea for preventing this type of ice build up?

I'm sorry, but I have tried to contact the furnace installer (out of business) and the furnace manufacturer (also out of business), and I cannot find out if any other company bought the furnace brand -- it was a brand I did not recognize, but the installer was reputable and recommended it. (We were told it was a HVAC "generic" brand -- just as good, but we would not be paying for the name brand -- yes, we were probably young and naive; but the installer was well known.)

We have had no problems with the furnace itself. I just worry about potential problems from the ice build up.

I tried insulating the outside part of the pipe last winter with a pipe wrap (no effect) -- probably a dumb idea, but it was suggested by a radio Handyman I called in desperation.

I've thought of putting on an extention to the pipe, pointing it up, but this is probably a dumb idea, too; snow and rain could get into the pipe and cause who knows what kind of problems.

Any ideas?


Get another HVAC tech (post #194656, reply #1 of 5)

out there to modify the vent pipe. It may be possible to run it uphill so that condensation runs back to the furnace and is drained inside rather than outside. 

I doubt that the ice buildup (post #194656, reply #2 of 5)

I doubt that the ice buildup will ever reach the point of actually clogging the exhaust vent. This is because the only time condensation forms and drips is during the times when the furnace is also exhausting hot exhaust gases, which will keep the ice from forming high enough to block the the exhaust.

There are thousands of houses in this area with the same exhaust configuration, and the winter temps can get to -30, which is probably almost as low as N. Mich.

For $70/$80 bucks you can get (post #194656, reply #3 of 5)

For $70/$80 bucks you can get a device that monitors temp in the house and will dial two or three phone numbers to alert you to a problem.  The one I saw tracks a min temp a max temp and has a water sensor too that you could put near a sump pump or water heater depending on which is more critical to your situation.  I think it also monitored the power and would dial you if the power was out for more than a hour.

Regardless of what you do with the furnace, I would think putting in something like this would be cheap insurance for a home that isn't lived in daily.  I would guess googling home monitors would bring them up.

Yeah, it's pretty unlikely (post #194656, reply #4 of 5)

Yeah, it's pretty unlikely that it will clog, since the (relatively) hot air will prevent ice from forming close to the outlet.

But you can see if an HVAC guy can slant the pipe a little more towards the furnace, so that it wll drain back more of the condensate vs having it drip out.  (And, though I've never seen such a thing, I suspect that someone somewhere makes a special safe condensate drain for these things, that you could place at a low spot in the pipe.)

And one of the autodialers is probably a good idea -- your furnace can fail for a dozen reasons besides ice buildup.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

   (And, though I've never (post #194656, reply #5 of 5)

   (And, though I've never seen such a thing, I suspect that someone somewhere makes a special safe condensate drain for these things, that you could place at a low spot in the pipe.)

Like maybe what is recommended for power vent water heaters that vent in pvc or abs--the instructions show a tee in the line with the small branch pointing down and connected to a flex line that has about an 8"  loop in it to act as a trap that stops exhaust gas from blowing past.