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How to avoid ice-clogged furnace air intake pipe?



 
 
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  #11  
Old February 4th 10, 01:32 AM posted to misc.consumers.house
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Posts: 91
Default How to avoid ice-clogged furnace air intake pipe?

In article ,
MNRebecca wrote:
Once or twice each winter, my furnace shuts down due to a clogged air
intake pipe. The pipe clogs in subzero weather or during/after a
blizzard, presumably because of snow/ice building up inside the pipe

[ ... ]

The intake and exhaust pipes (white plastic PVC pipes) vent to the
outside right next to each other, just a few inches apart, about 2.5
feet above the ground. Each bends 90 degrees in opposite
directions...the intake faces east and the exhaust faces west.


Any advice on how I can keep the intake pipe from clogging? Thanks so
much if you can help.


Cheap possible fix: Get an elbow that can be attached to your intake
pipe outside the house, pointing it down. That will keep snow, sleet,
hail, etc. from getting in. No need to glue it, just slide it on. If
it's loose and tends to fall off, secure it with a stainless steel
screw through the top, or drill a small hole through and drop in a
galvanized nail.

I really doubt that you have a condensation problem, as winter air is
generally very dry and wouldn't condense going into a warmer environment.
If, however, you're getting condensation from somewhere, you could
disconnect it from the furnace, cut a slot into that end an inch or so
longer than the flange on the furnace, and feed a heat tape through the
pipe to the outside. Use the slot to bring it out at the furnace, and
seal the slot with furnace tape.

The intake should slope down from the furnace end to the outside;
otherwise condensate would flow into your furnace, which would not
be good for it. (This could be a concern in warm weather, unless the
furnace blocks inlet/flue airflow when it's not running.)

If possible, adding a few feet of exhaust stack with an elbow and a
rain cap will help your furnace avoid pulling exhaust back into the
intake.


Gary

--
Gary Heston http://www.thebreastcancersite.com/

"It's kind of hard to rally 'round a math class."
Paul "Bear" Bryant
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  #12  
Old February 4th 10, 03:42 PM posted to misc.consumers.house
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Posts: 20
Default How to avoid ice-clogged furnace air intake pipe?

Thanks again, all, for the suggestions and the physics lessons!
R.
  #13  
Old February 4th 10, 05:05 PM posted to misc.consumers.house
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Default How to avoid ice-clogged furnace air intake pipe?

In article , MNRebecca wrote:
Thanks again, all, for the suggestions and the physics lessons!
R.



The installers are simple minded. Sometimes snow then water will get
into the switch. First the switch may shut off if there is no air flow,
but if there is some flow the switch can be damaged, and
you have to deal with getting parts. Just like my brothers
up maybe a couple feet, and snow drifts can get higher than that, and have in Md.,
and the forcast is for up to 36 inches in Md this weekend.
There is also a rule of staying away from chinneys and other walls, and optimun
pipe spacing between the 2 pipes is 3 feet.




greg
  #14  
Old February 9th 10, 10:30 PM posted to misc.consumers.house
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Posts: 20
Default How to avoid ice-clogged furnace air intake pipe?

Another question. Is it possible the builder/installer (furnace went
in during a major house renovation) made the intake pipe face east
(instead of down) to achieve a 180 degree variance with the exhaust
pipe? They're only a few inches apart. If I add some pipe and change
the intake direction from east to straight down, it'll only be 90
degrees different from the exhaust pipe opening. Have I just greatly
increased my likelihood of carbon monoxide poisoning (from the intake
pipe sucking in exhaust) or doesn't it matter much since it's only
going to get burned up in the furnace anyway?

By the way, I double-checked.
1) They really do face east (intake) and west (exhaust). I generally
think of the wind as coming primarily from the NW in my area, but I
guess it does come from E or SE about half the time.
2) The pipes are about 1 foot above the ground, not 2.5. Maybe the
intake doesn't face down for fear of a drift forming beneath it.
  #15  
Old February 9th 10, 10:49 PM posted to misc.consumers.house
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Default How to avoid ice-clogged furnace air intake pipe?

In article , MNRebecca wrote:
Another question. Is it possible the builder/installer (furnace went
in during a major house renovation) made the intake pipe face east
(instead of down) to achieve a 180 degree variance with the exhaust
pipe? They're only a few inches apart.


Very likely that's the reason.

If I add some pipe and change
the intake direction from east to straight down, it'll only be 90
degrees different from the exhaust pipe opening. Have I just greatly
increased my likelihood of carbon monoxide poisoning (from the intake
pipe sucking in exhaust)


Slightly increased, perhaps, but:
(a) if you don't already have a CO detector in the house, you should anyway;
(b) it's not rocket science to add elbows and extensions to the pipes to
increase the separation; and...

or doesn't it matter much since it's only
going to get burned up in the furnace anyway?


(c) most of it is going to get burned up in the furnace anyway.

By the way, I double-checked.
1) They really do face east (intake) and west (exhaust). I generally
think of the wind as coming primarily from the NW in my area, but I
guess it does come from E or SE about half the time.


You could check with the National Weather Service; they keep records of that
sort of thing.

2) The pipes are about 1 foot above the ground, not 2.5. Maybe the
intake doesn't face down for fear of a drift forming beneath it.


I'm sure that's the reason. It shouldn't be too hard to extend the pipe
upward, though, then put two elbows on it so the opening faces down but is
much higher above the ground.
  #16  
Old February 10th 10, 01:01 AM posted to misc.consumers.house
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Posts: 22
Default How to avoid ice-clogged furnace air intake pipe?

MNRebecca wrote:

Another question. Is it possible the builder/installer (furnace went
in during a major house renovation) made the intake pipe face east
(instead of down) to achieve a 180 degree variance with the exhaust
pipe? They're only a few inches apart. If I add some pipe and change
the intake direction from east to straight down, it'll only be 90
degrees different from the exhaust pipe opening. Have I just greatly
increased my likelihood of carbon monoxide poisoning (from the intake
pipe sucking in exhaust) or doesn't it matter much since it's only
going to get burned up in the furnace anyway?


First, there should be little to no CO in the exhaust unless the
furnace is defective. If the heat exchanger leaks, the intake air will
not be your problem. When the furnace is operating properly, the
exhaust is high in CO2 and water, and low in Oxygen. So, you have a
higher probability of sucking water into the intake, where it will
condense and freeze.

You might ask your gas company repair department what the code says
about this type of furnace. I suspect the installation is not up to
code, or is marginal.


By the way, I double-checked.
1) They really do face east (intake) and west (exhaust). I generally
think of the wind as coming primarily from the NW in my area, but I
guess it does come from E or SE about half the time.
2) The pipes are about 1 foot above the ground, not 2.5. Maybe the
intake doesn't face down for fear of a drift forming beneath it.


At that level a drift could cover either pipe regardless of
orientation...
  #17  
Old February 10th 10, 03:56 AM posted to misc.consumers.house
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Posts: 91
Default How to avoid ice-clogged furnace air intake pipe?

In article ,
MNRebecca wrote:
Another question. Is it possible the builder/installer (furnace went
in during a major house renovation) made the intake pipe face east
(instead of down) to achieve a 180 degree variance with the exhaust
pipe? They're only a few inches apart.


Unless the horizontal pipes are of significant length (say at least
two feet each), which direction they're pointing is not going to
matter much. In still air, some of the exhaust will get sucked into
the intake. Same if you have a breeze from the west.

If I add some pipe and change
the intake direction from east to straight down, it'll only be 90
degrees different from the exhaust pipe opening. Have I just greatly
increased my likelihood of carbon monoxide poisoning (from the intake
pipe sucking in exhaust) or doesn't it matter much since it's only
going to get burned up in the furnace anyway?


An elbow pointing down shouldn't make much difference; if you're worried
splice in a few feet of pipe to extend the horizontal separation, then
the elbow.

By the way, I double-checked.
1) They really do face east (intake) and west (exhaust). I generally
think of the wind as coming primarily from the NW in my area, but I
guess it does come from E or SE about half the time.
2) The pipes are about 1 foot above the ground, not 2.5. Maybe the
intake doesn't face down for fear of a drift forming beneath it.


There's not much difference if you only add an elbow, and it'd be
easier to clear a drift out from under it than to clean ice out of
the intake.

And, I concur with the recommendation that you should have a carbon
monoxide detector. For that matter, two wouldn't hurt--they're a lot
cheaper than a funeral. I've had them for years (I have gas convection
wall heaters).


Gary

--
Gary Heston http://www.thebreastcancersite.com/

"It's kind of hard to rally 'round a math class."
Paul "Bear" Bryant
  #18  
Old February 10th 10, 05:09 PM posted to misc.consumers.house
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Default How to avoid ice-clogged furnace air intake pipe?

The extra elbows and extenders...they're not going to make it too hard
for the furnace to get air through the intake pipe, are they?
  #19  
Old February 10th 10, 05:43 PM posted to misc.consumers.house
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Posts: 5,226
Default How to avoid ice-clogged furnace air intake pipe?

MNRebecca wrote:
The extra elbows and extenders...they're not going to make it too hard
for the furnace to get air through the intake pipe, are they?


A couple elbows shouldn't matter unless you have a lot of piping getting there.

On my house, the intake pipe comes out of the wall , with a downward facing
elbow to prevent water/dirt entry. The exhaust pipe has 2 elbows so it jogs
down, then points straight out from the wall so the exhaust is directed away
from the house and intake. A short length of pipe on the downward jog can be
used to keep it from hitting plants that might be damaged.

CO should not be an issue. If some exhaust gets drawn into the intake, it will
just go through the burner and right back out. It won't stay in the house.


  #20  
Old February 10th 10, 09:40 PM posted to misc.consumers.house
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Posts: 20
Default How to avoid ice-clogged furnace air intake pipe?

On Feb 10, 10:43*am, "Bob F" wrote:

A couple elbows shouldn't matter unless you have a lot of piping getting there.


Like 12 to 14 feet? The furnace is not against an external wall.
It's in an interior room surrounded by a basement addition. The
intake and exhaust pipes run about a dozen feet or so across the
basement ceiling before breaking through an external wall. Still okay
to add some extension and a few elbows outside?
 




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