How to avoid ice-clogged furnace air intake pipe?
MNRebecca
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.
krw
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.
John Weiss
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.
Doug Miller
>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.
Doug Miller
>On Tue, 2 Feb 2010 14:22:41 -0800 (PST), MNRebecca
><web...@morris.umn.edu> wrote:
>
>>Once or twice each winter, my furnace shuts down due to a clogged air
>>intake pipe.
>>Any advice on how I can keep the intake pipe from clogging?
>
>condensate runs back to a low spot and freezes.
Ummmm.....no, it doesn't sound like that at all, actually. Flue != intake.
MNRebecca
MNRebecca <web...@morris.umn.edu> 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),
spamb...@milmac.com (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)
Doug Miller
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.
Cindy Hamilton
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
Bob F
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.
krw
wrote:
Good point. I'd seen the issue with flues before.
Gary Heston
MNRebecca <web...@morris.umn.edu> wrote:
>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 ghe...@hiwaay.net http://www.thebreastcancersite.com/
"It's kind of hard to rally 'round a math class."
Paul "Bear" Bryant
MNRebecca
R.
GregS
>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
MNRebecca
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.
Doug Miller
>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.
John Weiss
> 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...
Gary Heston
MNRebecca <web...@morris.umn.edu> wrote:
>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).
MNRebecca
for the furnace to get air through the intake pipe, are they?
Bob F
> 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.
MNRebecca
> 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?
Doug Miller
>On Feb 10, 10:43=A0am, "Bob F" <bobnos...@gmail.com> 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?
If you're really concerned about that, add an adapter just outside to
transition to the next larger size of pipe, and make the extensions and elbows
in the larger size.
Bob F
That sounds very similar to mine.
You might be getting close to the limits. Reading the installation manual for
your furnace should give you the necessary info. I managed to get these for two
used furnaces by contacting the manufacturer. In one case, I had to talk to a
distributer in the end to get it. The other was easily downloaded.
You shouldn't need to add many elbows. At most, 2 on the exhaust outside, and
probably 1 on the intake should be all you need.
You could try just pressing the elbows on and see how it works. The furnace has
sensors that cause it to shut down if things aren't right. But don't go much
over waht the manual says.
Gary Heston
MNRebecca <web...@morris.umn.edu> 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?
I doubt it. You should have an owners' manual or some technical material
for your furnace (or look it up by searching for the model number). That
should have some information on the maximum intake/exhaust piping and
what diameter it should be.
John Weiss
> 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?
In general, no. However, check with your gas company or the
installation docs for the furnace. There may be stated limits or codes
that govern.
db3...@gmail.com
Bert
news:671b26b7-ea5d-4494...@z41g2000yqz.googlegroups.com
> 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.
the ground, like yours seems to be.
We've had a high-efficiency furnace with PVC intake and exhaust like
yours for more than 20 years and have never had a problem with snow
blocking the intake. We'll have icicles hanging from the exhaust, but
they don't block the pipe.
--
be...@iphouse.com St. Paul, MN
Bob F
warm the intake pipe so freezing could not occur. The trick would be how to
properly direct the exhaust air away from the intake inlet. Perhaps a "T"
fitting for the exhaust around the intake pipe, with the exhaust directed out at
a right angle away from the inlet.
mmaggi...@gmail.com
> 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.
ric...@comcast.net
ric...@comcast.net
web...@gmail.com
Toward the end of last winter I read this thread and got an 180 elbow to put on the intake, but just today (1st sub zero temp of the season) the intake frosted over again. I cleared and changed both elbows to face more directly east for exhaust and west for intake. But I'm wondering if the exhaust needs to have an elbow at all. Wouldn't it be better if it just blew straight up and let the wind take it from there?
Bob F
> I'm in Minnesnowda and I have this problem too with my roof top pvc intake and exhaust. The exhaust has an 180 elbow which tends to blow right toward the straight up intake.
>
> Toward the end of last winter I read this thread and got an 180 elbow to put on the intake, but just today (1st sub zero temp of the season) the intake frosted over again. I cleared and changed both elbows to face more directly east for exhaust and west for intake. But I'm wondering if the exhaust needs to have an elbow at all. Wouldn't it be better if it just blew straight up and let the wind take it from there?
>
the furnace or overworking the condensate pump.
web...@gmail.com
>
> The elbow probably keeps rain/crud from going down the pipe and damaging
> the furnace or overworking the condensate pump.
deprat...@gmail.com
rf5...@gmail.com
rf5...@gmail.com
gsfr...@gmail.com
> There are dampers available for furnace air intake vents and are relatively inexpensive, but are controlled electrically and may require a technician to install. Also this may not entirely solve the problem, especially when the outside air temperature is below zero. But will lessen the occurrence of frost build up.
Issues started happening January 2018 when it got very cold.
Short heating cycles on 2nd stage heat that were not heating up the house fast enough.
My furnace is new and under warranty. The technician came today and found that the gas pressure was too high and the safety switch was shutting down the furnace due to excessive heat.
He adjusted the gas pressure valve and it seems to be working right now.
charm...@yahoo.ca
Mark F
> I live in Manitoba and have the same issue. When I asked the technician about the exhaust and intake pipes (by the way, mine are not separate outside but are joined together just before exiting the foundation - should I be concerned about that?) and the slope of them, he brushed it off. After he left, second time, I went outside and I could actually look down into the pipe and see water droplets. I pushed the outside vent back on as it was barely attached and the furnace cut in and has been running fine since then. The guy never went outside to have a look. Just spent 2 hours running checks and looking for code issues and kept telling me the furnace was working even though the temp in the house was 17 and the thermostat was set at 21. I suspect I need to attach that exterior vent better but should I also replace it with 2 separate vents?
should be careful.
freem...@yahoo.com
mesh) used to keep debris or critters out of the pipe. The mesh creates more surface area, increases cooling and frost build up. Other internet experts recommend adding 90 degree bends or extensions to the pipe, but they don't say that each bend or extention increases distance, and resistance to airflow which can overwork your draft inducer, shortening it's life and decreasing efficiency.
I solved my problem by installing a 2 inch to 4 inch pvc pipe transition, I used 1/2 inch chicken wire as a critter shield, then painted it flat black. The system works, the flat black paint absorbs solar radiation adding just enough heat to stop frosting over. It was -30 degrees last winter and it never frosted over.
jroc...@gmail.com
fdwa...@gmail.com
> I’m having the same issues. I live in Alberta and it’s been around -35 to -42 the past few days and my 3” intake keeps getting frost built up in the inside until my furnace shuts off or just blows cold air. Can I still increase the pipe diameter as soon As it leaves the house? It does have a 90 facing down and slightly away from the exhaust that goes straight out. I’m getting tired of cleaning the frost out 3-5 times in 24 hours including the middle of the night.
I have been reading up on these high efficiency furnaces because like Jroc said, it is cold in Alberta right now. Condensation is dripping from the exhaust and building up from the ground until it reaches the exhaust/intake. This has kicked the furnace off in the past, they are smart enough to recognize what's happening... it hasn't happened in the past couple years because I go and knock the ice off and away from below it.
Installation manuals for these furnaces require a 1/4" drop in 1 foot towards (yes towards) the furnace. 8' would be a 2" drop slanted towards the furnace. They have a system that manages the condensation and it drains into the floor drain. I have to change mine and try that. It only drops towards the furnace 1" in 10'.
Don't take my word for it, download a couple high efficiency furnace installation manuals.
Cheers,
W
Craig Gerlach
As soon as gets cold outside it would ice up. I had a fix that worked until it was below zero F, and since my install is high on ground level floor and exhaust exits just under soffits, was to add 2' extension to the exhaust. More condensate was forming inside the pipe and then dripping to ground vs turning side of cabin into a cloud making machine like a dryer vent.
My 'furnace' can handle up to 15' of venting before I need to flip some DIP switches to change and can handle vents longer than my house, so adding this small section was of no concern.
Now that it is -25F out there, and near zero wind, the small amount of plume is now a concern again and I was outside middle of night clearing ice off intake, and again 6 hours later.
I was tempted to add small heater to intake, as I bought one to warm up my ATV, small 15w unit, but think will just extend intake when can make another trip to hardware store.
Add a 90 and run away from exhaust. If I didn't just have the whole house sided and new soffits I would build some sort of diverter between the 2.
I thought going 3" when 2" was only required due to short length would work, 1st heating season new system, guess I was wrong. At least with in floor heating, if it kicks off middle of night I only lose a few degrees of internal temps. They need to design a better intake/exhaust system for use in colder climates. Some low volt DC heater on intake with humidistat and thermostat sensors to trigger the need for heating. Or possibly reversing the intake and exhaust so warm air blows out intake and melts the buildup? Engineers get to work, this should not be upon the homeowner.
And if those ideas makes someone rich here, please come out and upgrade my system, I am too old for late night trips out in -40F windchills.