Venting

[Darren]

Must be my week for tough inspections; Today I had a 3 year old Coleman gas fired, induced fan vented furnace. Metal ‘B’ vent extended about 25 feet until it penetrated the foundation wall. There also was what appeared to be a barometric damper on the vent pipe about 5 feet from the furnace.

2 questions; what is the maximum length for an induced fan exhaust (horizontal) and what could possibly be the reason a damper was installed. I didn’t think a damper is allowed on a gas fired appliance. I have e-mailed Coleman with these questions, any help here would be appreciated.

Darren

[a46geo]

Darren,

The manufacturer is indeed the best place to go. They all have different installation limitations for different models and different years of production. Size of the pipe, bends, rise and even furnace size may all work to limit distance.

As far as the barometric damper. I would say no way.

[Darren]

George,

Do you think the damper was installed due to length of pipe?

Darren

[RobC]

The answer is:

0

and

not allowed.

I'll have the really big rubber baseball bat on the second shelf, next to the pink elephant.

[a46geo]

Darren,

One never knows just why some people do the things that they do or what they think they are going to accomplish, but I have never come across any mfg installation instructions that called for such a thing.

In my opinion it should be removed.

George

[RobC]

Darren,

From my conversation with the authorities on another matter a few post over, the maximum horizontal distance they've ever seen is 20'.

The allowed distance varies according to manufacturer spec.