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How to avoid ice-clogged furnace air intake pipe?



 
 
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  #1  
Old February 2nd 10, 10:22 PM posted to misc.consumers.house
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Posts: 20
Default How to avoid ice-clogged furnace air intake pipe?

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
(said the repair guy after traveling out in a blizzard on Sunday
morning the first time it happened). If I disconnect the pipe from
the furnace and let it draw air from the room instead (which I'm told,
by the repair guy, is harmless), it fires back up and runs fine. But
I hate the idea that, each year, I have to live in dread of the time
I'll wake up in the middle of the night to a disturbingly cold house
and then have to live with a furnace drawing air from a basement room
instead of outside (until temps outside climb above freezing, which
can be weeks).

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.
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  #2  
Old February 2nd 10, 11:21 PM posted to misc.consumers.house
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Posts: 613
Default How to avoid ice-clogged furnace air intake pipe?

On Tue, 2 Feb 2010 14:22:41 -0800 (PST), 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
(said the repair guy after traveling out in a blizzard on Sunday
morning the first time it happened). If I disconnect the pipe from
the furnace and let it draw air from the room instead (which I'm told,
by the repair guy, is harmless), it fires back up and runs fine. But
I hate the idea that, each year, I have to live in dread of the time
I'll wake up in the middle of the night to a disturbingly cold house
and then have to live with a furnace drawing air from a basement room
instead of outside (until temps outside climb above freezing, which
can be weeks).

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.


It sounds like your flue is tilted back towards the house so the
condensate runs back to a low spot and freezes. If this is the
problem, you should put a pretty good pitch on it so all condensate
runs out of the pipe before it can freeze. Another possibility is
that the flue is too long causing a similar problem (freezing before
running out of the pipe). In either case the fix shouldn't be too
complicated. If you can't change the pipe slope or length, perhaps
some insulation is in order.
  #3  
Old February 2nd 10, 11:41 PM posted to misc.consumers.house
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Posts: 22
Default How to avoid ice-clogged furnace air intake pipe?

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
(said the repair guy after traveling out in a blizzard on Sunday
morning the first time it happened). If I disconnect the pipe from
the furnace and let it draw air from the room instead (which I'm told,
by the repair guy, is harmless), it fires back up and runs fine. But
I hate the idea that, each year, I have to live in dread of the time
I'll wake up in the middle of the night to a disturbingly cold house
and then have to live with a furnace drawing air from a basement room
instead of outside (until temps outside climb above freezing, which
can be weeks).

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.


I suspect rain and/or snow are blowing (or being sucked) into the
intake at times, along with moist exhaust air. I'd put an extension on
one or both to move the openings further away, then possibly put
another elbow on the intake so it points downward.

Another approach would be to add a "dorade box" (used for on-deck air
vents on sailboats to prevent water from entering) over the intake
pipe. Build a simple wooden box around the pipe end (which points
sideways or upward), attached/sealed to the house, with an opening in
ther bottom of the box. Leave enough room inside the box for free
airflow through it.
  #4  
Old February 3rd 10, 12:10 AM posted to misc.consumers.house
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Posts: 6,380
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
(said the repair guy after traveling out in a blizzard on Sunday
morning the first time it happened). If I disconnect the pipe from
the furnace and let it draw air from the room instead (which I'm told,
by the repair guy, is harmless),


He's right. It's less energy-efficient, because cold air is drawn into the
house to make up for it, but it won't harm anything (other than your bank
balance).

it fires back up and runs fine. But
I hate the idea that, each year, I have to live in dread of the time
I'll wake up in the middle of the night to a disturbingly cold house
and then have to live with a furnace drawing air from a basement room
instead of outside (until temps outside climb above freezing, which
can be weeks).

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.


(You sure you don't have that backwards?) That's probably most of the problem
right the the pipes face the wrong directions. The intake should face DOWN
so that rain and snow can't get into it. And the exhaust should face east, not
west: in most of North America, the wind comes from the west much more
frequently than from the east. You want the exhaust to be moving in the same
direction as the wind, not into the wind.

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

  #5  
Old February 3rd 10, 12:12 AM posted to misc.consumers.house
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Posts: 6,380
Default How to avoid ice-clogged furnace air intake pipe?

In article , krw wrote:
On Tue, 2 Feb 2010 14:22:41 -0800 (PST), MNRebecca
wrote:

Once or twice each winter, my furnace shuts down due to a clogged air
intake pipe.

[snip]
Any advice on how I can keep the intake pipe from clogging?


It sounds like your flue is tilted back towards the house so the
condensate runs back to a low spot and freezes.


Ummmm.....no, it doesn't sound like that at all, actually. Flue != intake.
  #6  
Old February 3rd 10, 02:21 PM posted to misc.consumers.house
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Posts: 20
Default How to avoid ice-clogged furnace air intake pipe?

Thanks for all the feedback, everybody. I'll look it over thoroughly.

MNRebecca wrote:
*If I disconnect the pipe from
the furnace and let it draw air from the room instead (which I'm told,
by the repair guy, is harmless),


(Doug Miller) wrote:
He's right. It's less energy-efficient, because cold air is drawn into the
house to make up for it, but it won't harm anything (other than your bank
balance).


I'm a little confused by this. The intake pipe draws cold air from
outside. The air in the room is far warmer. Where/how is cold air
being drawn into the house to make up for the fact that I disconnected
the intake pipe and made the furnace use room air instead?

R. (really appreciates what she's learning)
  #7  
Old February 3rd 10, 03:20 PM posted to misc.consumers.house
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Posts: 6,380
Default How to avoid ice-clogged furnace air intake pipe?

In article , MNRebecca wrote:
Thanks for all the feedback, everybody. I'll look it over thoroughly.

MNRebecca wrote:
If I disconnect the pipe from
the furnace and let it draw air from the room instead (which I'm told,
by the repair guy, is harmless),


(Doug Miller) wrote:
He's right. It's less energy-efficient, because cold air is drawn into the
house to make up for it, but it won't harm anything (other than your bank
balance).


I'm a little confused by this. The intake pipe draws cold air from
outside. The air in the room is far warmer. Where/how is cold air
being drawn into the house to make up for the fact that I disconnected
the intake pipe and made the furnace use room air instead?


When the furnace uses room air instead of outside air, air has to come from
somewhere to replace it. Where do you suppose it comes from?

*All* air that the furnace uses for combustion comes from outside the house,
in the long run. The point of having an outdoor intake for the furnace is so
that the combustion air comes *directly* from outside the house, straight into
the furnace. If the furnace is burning room air instead, that creates a slight
negative pressure in the house, and cold air comes in through various cracks,
leaks, holes, etc.
  #8  
Old February 3rd 10, 06:12 PM posted to misc.consumers.house
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Posts: 253
Default How to avoid ice-clogged furnace air intake pipe?

On Feb 3, 9:21*am, MNRebecca wrote:
Thanks for all the feedback, everybody. *I'll look it over thoroughly.

MNRebecca wrote:
*If I disconnect the pipe from
the furnace and let it draw air from the room instead (which I'm told,
by the repair guy, is harmless),

(Doug Miller) wrote:
He's right. It's less energy-efficient, because cold air is drawn into the
house to make up for it, but it won't harm anything (other than your bank
balance).


I'm a little confused by this. *The intake pipe draws cold air from
outside. *The air in the room is far warmer. *Where/how is cold air
being drawn into the house to make up for the fact that I disconnected
the intake pipe and made the furnace use room air instead?


Doug's answer to this question was good, but I think he fell into the
trap of knowing too much about the issue and giving not enough
information.

Your furnace blows exhaust (air) out the "chimney" (a PVC pipe in your
case)
when it runs. This tends to decrease the air pressure inside your
house, since
there's less air inside.

Normally, your furnace pulls air in through the intake pipe and this
balances the
pressure, but when you disconnect it and use "inside air", air from
outside moves
toward the area of lower pressure (inside your house), through
whatever gaps it
can find (around windows, doors, etc.) This air is colder than the
air
inside your house, which will make your furnace run more to keep the
air in your
house at the temperature set by your thermostat.

Cindy Hamilton
  #9  
Old February 3rd 10, 11:14 PM posted to misc.consumers.house
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Posts: 5,196
Default How to avoid ice-clogged furnace air intake pipe?

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
(said the repair guy after traveling out in a blizzard on Sunday
morning the first time it happened). If I disconnect the pipe from
the furnace and let it draw air from the room instead (which I'm told,
by the repair guy, is harmless), it fires back up and runs fine. But
I hate the idea that, each year, I have to live in dread of the time
I'll wake up in the middle of the night to a disturbingly cold house
and then have to live with a furnace drawing air from a basement room
instead of outside (until temps outside climb above freezing, which
can be weeks).

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.


A downward facing intake opening would be the first thing I'd try.

You could use concentric PVC pipes, with the intake being the one in the center,
which would keep it warm to prevent freezing. Perhaps a 2" intake pipe, with a
4" exhaust pipe around it. The plumbing at the ends might be interesting. Proper
slope would be important.


 




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