# Blocked Air Intake Vent Shuts-down and Stops High Efficiency Furnace in Winter



## beenthere (Oct 11, 2008)

Actually, the air never holds more then 100% RH. If air/exhaust from the exhaust pipe is reaching the intake, it isn't installed right.

Many manufacturers don't use the tee configuration yours does, and they don't have a problem.


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## hvac instructor (Jun 8, 2012)

a nice concentric works well


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## yuri (Nov 29, 2008)

hvac instructor said:


> a nice concentric works well


 as long as you pull the donut hood off and clean the spiders webs out once in a while.


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## yuri (Nov 29, 2008)

That tee config is what they use after they test the setup in calm conditions. Has to be far enough away to not recirc. Has to do with the velocity of the discharge and how much suction the intake has also. Lennox uses an accelerator in their exhaust pipe and shoots it far out and is a rather clever and cool method.


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## Ralph_handy (Jan 4, 2014)

beenthere said:


> "Actually, the air never holds more then 100% RH."
> Rain, snow or sleet comes from air exceeding 100% humidity, water condensing on particles (dust) in the air (forming clouds), and the fine droplets combining to form rain drops. As moist warm air rises, it gets cold in the upper atmosphere and becomes supersaturated (exceeding 100% humidity).
> 
> Similar conditions can occur as the air near the ground cools during the evening. The result is dew or frost on the ground.
> ...


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## beenthere (Oct 11, 2008)

Ralph_handy said:


> beenthere said:
> 
> 
> > "Actually, the air never holds more then 100% RH."
> ...


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