From: MNRebecca on
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.
From: krw on
On Tue, 2 Feb 2010 14:22:41 -0800 (PST), MNRebecca
<webbrl(a)morris.umn.edu> 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.
From: John Weiss on
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.
From: Doug Miller on
In article <671b26b7-ea5d-4494-bd26-847a01ebe99d(a)z41g2000yqz.googlegroups.com>, MNRebecca <webbrl(a)morris.umn.edu> 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 there: 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.
From: Doug Miller on
In article <rjchm59vre4fp1t82f5hlls5anr89up44k(a)4ax.com>, krw <krw(a)att.bizzzzzzzzzzz> wrote:
>On Tue, 2 Feb 2010 14:22:41 -0800 (PST), MNRebecca
><webbrl(a)morris.umn.edu> 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.