Iced Furnance Air Intake


M

MC

Dear All,

Outside winter temperature often reached -30 C. The fresh air intake iced up
resulting in furnace shut down. The furnace is 1 year old, high efficiency,
forced air furnace.

The intake is a 2.5" OD black PVC pipe.

The cloth dryer's exhaust vent is about 6' below and 3' displaced from the
furnace air intake.

Other than moving the clothing exhaust vent elsewhere, any suggestion to
avoid having to remove the loose ice from the air intake?

No problem when the cloth dryer is not running.

Thanks,
MC
 
P

PeterD

Dear All,

Outside winter temperature often reached -30 C. The fresh air intake iced up
resulting in furnace shut down. The furnace is 1 year old, high efficiency,
forced air furnace.

The intake is a 2.5" OD black PVC pipe.

The cloth dryer's exhaust vent is about 6' below and 3' displaced from the
furnace air intake.

Other than moving the clothing exhaust vent elsewhere, any suggestion to
avoid having to remove the loose ice from the air intake?

No problem when the cloth dryer is not running.

Thanks,
MC
My first thought is that you should consider whether it is possible to
recycle the dryer exhaust and use that heat (and moisture) in the
building...

Other than that, extend the dryer exhaust above the furnace intake, or
more the furnace intake down below the drier?
 
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W

willshak

Dear All,

Outside winter temperature often reached -30 C. The fresh air intake iced up
resulting in furnace shut down. The furnace is 1 year old, high efficiency,
forced air furnace.

The intake is a 2.5" OD black PVC pipe.

The cloth dryer's exhaust vent is about 6' below and 3' displaced from the
furnace air intake.

Other than moving the clothing exhaust vent elsewhere, any suggestion to
avoid having to remove the loose ice from the air intake?

No problem when the cloth dryer is not running.

Thanks,
MC
I'm not a furnace expert, but what does the dryer vent have to do with
the furnace fresh air intake? Are they connected?
Where does the furnace air intake draw the air from?
 
W

Wayne Whitney

I'm not a furnace expert, but what does the dryer vent have to do with
the furnace fresh air intake? Are they connected?
The point is that the dryer vent is exhausting warm, moist air; as the
exhaust cools to ambient below freezing temperature, some of the
moisture condenses out and freezes. Since this is all happening near
the furnace intake, some of that ice ends up at the furnace intake
vent or in the intake pipe; over time it can build up and restrict the
pipe enough to cause a problem.

Cheers, Wayne
 
W

willshak

The point is that the dryer vent is exhausting warm, moist air; as the
exhaust cools to ambient below freezing temperature, some of the
moisture condenses out and freezes. Since this is all happening near
the furnace intake, some of that ice ends up at the furnace intake
vent or in the intake pipe; over time it can build up and restrict the
pipe enough to cause a problem.

Cheers, Wayne
I'm still at a loss.
Shouldn't the clothes dryer have an exhaust vent to the outside? Is it
exhausting into the room?
Is this the same guy that's over in alt.home.repair that complains of
having to clean lint out of his bathroom fan once a month? :)
 
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W

Wayne Whitney

Shouldn't the clothes dryer have an exhaust vent to the outside? Is it
exhausting into the room?
This is a sealed combution furnace, so its air intake is outside.

Wayne
 
M

MC

To Group,

I seem to get two suggestions so far:
1) Heat traced it.
2) Heat trace not suitable because the pipe is plastic.

Questions:
a) How hot can the heat trace wire get to? Can the PVC pipe (the kind one
can buy from any construction outfit) take the heat safely?
b) If it is safe, how shall one proceed to heat trace it. The loose ice
accumulates near the entrance grill only. The body of the pipe is never
plug. It is the accumulation of loose ice from the moisture of the dryer
vent at the intake grill that will eventually restrict the air intake so
much that the safety mechanism of the furnace shuts down the heating cycle.

Thanks in advance,
MC
 
D

Dennis

If you paid to have the furnace installed, contact the seller and ask him to
make the necessary changes (I believe that you are supposed to maintain 6'
from a dryer exhaust for just this problem). If not, it appears you have two
choices. One is to install an elbow and run the intake to a higher level.
The second is to close off the existing inlet and route a new one to a
different location. (Or perhaps you could reroute the dryer. But do not
terminate the dryer exhaust inside the home. The additional moister load
will cause untold problems inside the walls.)
 
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Joined
Feb 11, 2014
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Hello, I have propane furnace venting to roof that has thick heavy ice buildup.
The intake freezes up and shuts down furnace and all pipes etc frozen. We have used poles to knock ice off chimney each year. But only takes one mistake to freeze up house. Twice now in 12 years. There are no other sewer or dryer or kit/bath fans venting near the chimney. Near International Peace Gardens in ND. Put in new furnace two years ago to fix the problem. It did not. Contractors said some federal regulation requires newer furnaces to have exhaust vent pipe inside the combustion air intake pipe on the roof. Any ideas on how to "fix" this?
 

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