Landlord

[lanemark]

I recently purchased a home in Montana. For the past several weeks we have experienced sub-zero temperatures with the temperatures dipping as low as -20 degrees. When I awoke this morning I noticed our gas fired Armstrong heater was not working. I went downstairs to investigate. The fan motor would run for about 20 seconds and then turn off. It would remain off for about another 20 seconds and then kick back on and continued this same cycle for the few minutes I was downstairs. I shut the system off and called a heating and air conditioning service.
They discovered that my exhaust pvc pipe was frozen shut. The intake and exhaust exit the house just above the basement wall and under our front deck. When I crawled under the deck with the service repairman I noticed long thick icicles hanging from the floor joists of the deck on either side of the exhaust pipe. I noticed that the intake and vent pipes entered the outside of the house directly between two floor joists (16 inch centered). It appeared to me that the exhaust was being trapped on four sides.....the decking boards, the two floor joists and the side of the house.( and the ground). My guess is that condensation was being formed by the warmer exhaust air and the icey outside air and forming ice on the floor joists until the ice built up enough to actually close the exhause pipe hole.
Here's some other information that may or not be pertinent to this problem.
1) intake and exhaust pipes only extend about 5 inches out from the foundation;
2) The end of the exhaust pipe is only about 4 or 5 inches from a floor joists and blows directly into the floor joists where the ice has built up.
3) There is only about three feet of distance from the top of the deck to the ground underneath the deck.
3

After clearing the exhaust pipe of the ice the heater worked fine.

My questions: Does this sound like a proper installation, and if not, what would be the proper installation of the pipes? Could I extend the exhaust pipe so that the exhaust is released without being restricted by the floor joists and decking boards? If so, is there a limit to the distance I could extend the pipe? Any advice would be appreciated. Thanks

[cmajerus]

depends on the model of furnace, and the length of pipe already. We have extended pvc all the way out the end of decks in situations like yours, but it all depends on the application.

[jwiehagen76]

Intake and exhaust should not be installed under any structure. Pipe length, size and application are important factors. You will have a recurring problem if not corrected. Have a qualified installer repipe system with the correct size free of obstruction. That more than likely solve issue.

[DanW13]

Those intake and exhaust pipes need to have fresh air moving the exhaust air from the building and to keep those pipes from freezing close as they have already done and should have never been installed under your porch or anyones porch with poor ventilation. Move the pipes to a different side of the home and have the up high enough to clear any snow fall and still be atleast 12" above the average snow fall for you area. Unless you like having to climb under you porch all the time I would have it moved.

[captube]

Whats landlord got to do with this?

[lanemark]

Those intake and exhaust pipes need to have fresh air moving the exhaust air from the building and to keep those pipes from freezing close as they have already done and should have never been installed under your porch or anyones porch with poor ventilation. Move the pipes to a different side of the home and have the up high enough to clear any snow fall and still be atleast 12" above the average snow fall for you area. Unless you like having to climb under you porch all the time I would have it moved.
Your recommendation makes good sense to me. To your knowledge is there a maximum distance that these pipes can extend? Right now both pipes run about 10 feet before they exit the house. I could run both pipes to the opposite side of the house but it would mean running both pipes a distance of about 30 feet from the furnace. Any problem with that?

[lanemark]

One additional question.....right now both pipes are 2 inch pvc. Would I have to use a bigger diameter pipe if I increase the distance the pipe extends?

[jrbenny]

One additional question.....right now both pipes are 2 inch pvc. Would I have to use a bigger diameter pipe if I increase the distance the pipe extends?

It depends on how long the pipe run is already. (Now you know why you should never terminate vent pipes under a deck. ;))

[pecmsg]

Your recommendation makes good sense to me. To your knowledge is there a maximum distance that these pipes can extend? Right now both pipes run about 10 feet before they exit the house. I could run both pipes to the opposite side of the house but it would mean running both pipes a distance of about 30 feet from the furnace. Any problem with that?

Please don’t do this yourself.

[lolson]

(Now you know why you should never terminate vent pipes under a deck. ;))

That happens way to often. and then again some decks get build after the fact :D

[heaterman]

On the surface the solution seems easy enough. All furnaces have different requirements as far as allowable vent length, diameter and even how they are terminated. There are also local codes that come into play in some areas. In this case, the best solution is to have a reputable HVAC contractor re-vent the system for you. They will stand behind their work and you won't do any harm to your equipment or home.

[lanemark]

Sound advice....thanks....I planned on having the work done by a professional but I like to arm myself with as much information as possible before arranging to have the work done. There are some unscrupulous companies around and I feel that the more knowledge I have when dealing with them the less likely someone is going to try to "pull the wool over my eyes".
I'm taking your advice but I do feel more reassured as a result of some of the information I've gained from some of the other posters here. Thanks again.

[Shophound]

It's not just the ice build-up under the deck that's a problem. There are no doubt times you run your furnace when outdoor temperatures are above freezing. During those times, the exhaust from your furnace is still condensing on the deck structural members, only as water vs. ice. Super-saturating your deck's wooden structural members can do no good for them...i.e. ROT!

The exhaust needs to be moved away from the deck. Ask your friends and neighbors for any positive experiences they've had with HVAC contractors, and then hire one of their recommendations to correct your problem.