Ice forming around exhaust/intake pipes outside

[Bunny Laroche]

Hi. We installed a new hot water heating (hydronic) system this year and it has been running deliriously fantastic. However, my GF has noticed that a considerable amount of ice is starting to build up around the 2" exhaust and air intake pipes immediately where they exit the house.

The pipes exit through a piece of treated plywood that covers an old basement window. The pipes come out of holes in the plywood about 12 inches above grade. A 90 degree elbow in each pipe, installed immediately upon exiting the house, orients the pipes vertically for an additional 24 inches. 45 degree fittings are then positioned the end of each pipe, oriented in opposite directions (about 5 and 7 o'clock), about 6-8 inches apart.

Although there is a noticeable drip of condensate from the exhaust pipe, the dripping condensate is captured and does not pose any problems (so far). The ice build up that is somewhat concerning is forming all around the two pipes right where they exit the house. In addition to forming between the pipes, the ice is also adhering to the plywood through which the pipes exit. Insulation in the framework on the interior side of this plywood also has enough frost/ice build up to have frozen the batted insulation to the interior side of the plywood so that it cannot be pulled back.

Our primary concern is whether or not there is any ice build up inside either of the pipes. If so, how we might best go about melting it in order that the boiler does not go into a protective shut down mode if it can not either exhaust or intake?

My GF tried to fish a tape through the pipes to determine whether or not she could detect any ice build up on the inside of the pipes. As far as she could get the fish tape, past two 90 degree elbows to right about where the pipe exists the plywood, the fish tape did not appear to be hitting upon any ice, but we are not absolutely convinced since the fish tape stopped short.

Is the ice build up outside the pipes anything to be overly concerned about? Could the ice crack the pipes maybe? Or might ice around the pipes induce ice to form on the inside of the pipes if it has not already begun or done so?

Would it be a good idea to try and melt the ice build up around the pipes outside? My GF is an electrician and is proficient using both a heat gun as well as a propane torch if it is required or could help. Perhaps just pouring boiling hot water over the ice formation and pulling the ice away from the pipes and plywood, drying whatever moisture is left behind afterward, would be a better way to deal with the problem?

We are also concerned about the possibility that melting moisture could at some point run down inside the air intake pipe where the gas combustion occurs, causing possible problems later on?

Do you think the ice build up is simply due to condensation building up on the outside of the exhaust pipe as the warm air in the pipe meets the cold air outside?

Thank you for taking the time to read my post and happy New Year everybody.

 

[FullySprinklered]

I don't work on boilers and they're not that common in my part of the world, but I will say that after reading your post I've tried putting my pipe wrench back in my tool box, but the lid won't close.

 

[Sponsor]

 

[Smooky]

Only thing I can say is: For new sidewall-vented appliances always follow manufacturer installation instructions and adhere to your local codes such as: mechanical, building, city, etc.

I would want a good carbon monoxide detector with fresh batteries.
See if any of this helps:
http://inspectapedia.com/chimneys/Direct_Vent_Flue_SNAFU.php

 

[NY_Rob]

Ice buildup around the exhaust vent area of a mod-con is fairly common in areas where there is no time for it to thaw.

I doubt ice could form inside the exhaust pipe because it's usually pumping 100-140F+ air, and the intake is just pulling in outdoor air at fairly low velocity. With that in mind, I do recall reading there were maximum recommended outdoor lengths for PVC exhaust piping on mod-cons to prevent ice buildup inside the pipes.

If you can post photos of the intake and exhaust piping where it exits the house it would be helpful.

 

[Jadnashua]

You must ensure you have the proper slope to the exhaust line so that any condensate flows back to the sump. And, the terminal fittings and their positions must be correct. When I had my condensing boiler installed, the terminal vent was installed upside down, and the exhaust was above the intake (might seem logical) but when the exhaust condensed outside, it dripped down on the inlet side of the vent, and on a really cold day, caused the boiler to shut down because the inlet was then frozen closed from sucking in and being dripped on, the moisture from above (the vent has a baffle in it to prevent mixing of the intake and outlet when installed properly). The instructions clearly showed it installed opposite to how it was installed, and when I called them back, they changed it, and it has worked fine for years since.

You need to follow ALL of the instructions for routing, overall length, slope, and termination of the venting in the manual, or you can have problems. SO, yes, if not installed properly, it could cause the boiler to shut down.

 

[Dana]

The minimum separation between the intake & exhaust venting may have been violated if they're really only 6-8" apart. On page 21 of the UFT installation manual it reads:

"For sidewall venting, the minimum horizontal distance between adjacent exhaust vent terminations is 1 foot. It is recommended this distance be greater than 1 foot to better avoid frost damage to building surfaces."