Vertical Vent & power Question

[Apiernot]

I plan on putting a 75k NG unit in my 950sqft. attached garage in a few days. I am debating about a veritical vent or horizontal vent. My concern with the vertical vent is putting a hole in the roof and shingles. I am unsure how to seal this hole correctly so that I dont end up with moisture damage to my roof and subsequently the home in general. For those of you that have done the install; how did you seal the roof around the vent? Any help or ideas here would be appreciated. Pics are also a plus as this will be my first garage heater install.

One other question I have is about the electrical for the unit. Does the unit have to be on its own circuit or can it be tied into an existing circuit provided it wont cause an overload?

 

[Eggman]

If the 75k ng unit is an 80% unit, you can do either inside with a metal double wall flue. However, you will have to go verticle once outside the garage with the 80% unit to get above the roof line per code. If the furnace is a 90% high efficiency unit, then you can run a 2" pvc pipe flue out the side of the garage with a slope back to the furnace for the moisture to drain out to a floor drain. Once through the side of the garage, continue straight about 12" and put the small screen that came with it on. This has to exit above any possible snow line for venting purposes.

Eggman

When running electrical for a furnace, a separate circuit is recommended by most manufacturers. Some require it for the higher efficiency units because of the sensitiveness of the controls. 15 amp is usually enough unless you are adding a humidifier, the I would run a 20 am circuit.