• How to avoid ice-clogged furnace air intake pipe?

    From webwzrd@gmail.com@21:1/5 to All on Sat Dec 10 12:10:00 2016
    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?

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  • From Bob F@21:1/5 to webwzrd@gmail.com on Sat Dec 10 13:27:24 2016
    On 12/10/2016 12:10 PM, webwzrd@gmail.com wrote:
    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 elbow probably keeps rain/crud from going down the pipe and damaging
    the furnace or overworking the condensate pump.

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  • From webwzrd@gmail.com@21:1/5 to Bob F on Sun Dec 11 12:20:02 2016
    On Saturday, December 10, 2016 at 3:28:11 PM UTC-6, Bob F wrote:

    The elbow probably keeps rain/crud from going down the pipe and damaging
    the furnace or overworking the condensate pump.

    You're probably right. I'm hoping re-positioning the direction of the pipes will help. I'll be taking off for the holidays and it will be bad news if it frosts over while gone.

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  • From depratogianni@gmail.com@21:1/5 to All on Mon Dec 26 23:11:22 2016
    I have the same problem, luckily i have one of those wifi thermostats and the furnace sends an email when there is an alarm, on my lennox the alarm mentins something about a rollout switch whenever the intake is clogged? This last time i was in Hawaii
    and it was -32 C in Edmonton when i got the email, it really is a handy feature, ata minimum even with an older furnace you can at least check the temp from anywhere, i think i will try some of the recommendations in this thread with adding a divider or
    modifying piping, my intake points down but sits right between the hwt exhaust and durnace exhaust, i am sure that humidity is causing the intake buildup

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  • From rf56437@gmail.com@21:1/5 to All on Thu Jan 26 04:51:11 2017
    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.

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  • From rf56437@gmail.com@21:1/5 to All on Thu Jan 26 04:28:05 2017
    I believe the problem of frost build up occuring, is from a warmer intake vent temperature and extremely cold air drawn together. Not unlike the frost in a poorly sealed freezer or on old windows. When the colder outside air is drawn into the vent pipe,
    upon mixing with the warmer air radiating within the pipe the moisture from the cold air converts to frost. The solution may be to create a trap, limiting warm air from moving out through the pipe. Something as simple as a damper or flapper type of trap.
    Exhaust fans have a flapper to only allow air out, and doing this in the reverse may be the easiest fix. The furnace shuts down when the intake is restricted, because it has a pressure switch in the combustion box that senses vaccume pressure. Any
    flapper or damper would have to be opened easily and fully by the combustion fan..

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  • From gsfreitas@gmail.com@21:1/5 to rf5...@gmail.com on Fri Jan 19 12:19:40 2018
    On Thursday, January 26, 2017 at 7:51:13 AM UTC-5, rf5...@gmail.com wrote:
    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.

    My high efficiency furnace uses a concentric vent pipe for exhaust/intake. 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.

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  • From charmaupin@yahoo.ca@21:1/5 to All on Thu Mar 8 11:39:09 2018
    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?

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  • From Mark F@21:1/5 to charmaupin@yahoo.ca on Thu Mar 8 19:00:23 2018
    On Thu, 8 Mar 2018 11:39:09 -0800 (PST), charmaupin@yahoo.ca wrote:

    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?

    Did you check for Carbon Monoxide issues? With a loose vent pipe you
    should be careful.

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  • From freeme1962@yahoo.com@21:1/5 to All on Thu Dec 12 09:36:49 2019
    I've had this problem as well. It's generally not 'water' freezing in the intake pipe, it's due more to the fact your intake and exhaust ducts ate too close together, the exhaust releases warm exhaust with condensate (warm moist gases), which are drawn
    to the nearby intake. The problem is exacerbated if your intake vent/pipe has a mesh screen, (wire or pvc
    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.

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  • From jrockarts@gmail.com@21:1/5 to All on Mon Jan 13 04:58:09 2020
    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.

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  • From fdwadman@gmail.com@21:1/5 to jroc...@gmail.com on Mon Jan 13 15:06:51 2020
    On Monday, January 13, 2020 at 5:58:11 AM UTC-7, jroc...@gmail.com wrote:
    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.

    Hey all,

    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

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  • From Craig Gerlach@21:1/5 to All on Sun Feb 7 10:12:15 2021
    Trying to work out same issue on an Instant On Takagi Hot Water Heater using for radiant floor heat.
    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.

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