On Monday, January 13, 2020 at 5:58:11 AM UTC-7, wrote:
Im having the same issues. I live in Alberta and its 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. Im 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