Furnace wall exhaust, how close to soffit?

[Kev442]

Just got done hooking up my free 85k btu furnace today. I have it elevated 26" above the floor, so the pvc exhaust would start at 76". Assuming it should go straight up for roughly 24" before making an elbow to go through the wall, that is 102" on a 120" tall wall, or only 18" below the soffit. Pretty close for moisture laden exhaust air. I'm thinking I should make a U shape and have it go through the wall around 80-90" or so?

 

[mitymouse]

If I understand this, Making a u shape will not work. A high eff. furnace needs to have slope in the pvc back to the furnace to allow condensation drainage, and most require minumum of 15 feet of venting. takinf into account that a 90 degree elbow is the eqivelent of 5 feet of pipe.
is the soffit vented where you are planning to exit?

 

[Kev442]

Yes, the soffit is 24" vented over the garage attic, not too keen on the exhaust getting into it, it's a roughed in room in attic up there. Not that I go up there very often.
I can take it across the garage and vent on the other side, that would be 40' total straight with one elbow, will it be happier that way?

 

[mitymouse]

That makes a 45 foot run, Im not sure what this furnace requires for a max. run in 2 inch pvc but I think you be just fine as long as you maintain slope back to the furnace. If the room above the furnace is a "rough in" do you have a chase or wall cavity that 2 inch pvc would fit in, if so go through the roof

 

[Kev442]

For some reason, maybe to avoid icing up on the exit, all the pvc gets necked up to 3" or even 4" immediately upon exiting the furnace around here.

 

[mitymouse]

Not sure what your furnace requirements are. I do know lennox furnaces [depending on btu.] actually reduce in size before they exit the wall to help with velocity. I cant see an 85.000 btu requiring more then 3 inch pvc for less then 75 feet.
maybe look up the install manual for your furnace and see what the venting requirements are. each furnace is alittle different.
sorry I couldnt be more help