Gas company red tags furnace

[mathew stouffer]

Got a call the other day asking me to verify if there was enough combustion air in the attic for a furnace located in the space. They said the gas company red tagged the furnace and shut if off because they 'thought" there was not enough combustion air. Have you ever heard of this. I asked if the guy performed any calculatons to determine the amt of combustion air, she said nope. Ever hear of this.

[Markus Keller]

On an attic furnace, No. On various furnaces and water tanks stuffed into closets with solid doors, Yes.
I don't know what it is like around there but here the gas company errs on the side of caution. Any signs of flame roll out or excess confinement and they will shut it down. He may have looked up there and seen bad signs with the unit or no attic venting at all. Flame roll out, insulation/wood contact etc. The combustion air might have just been a quick excuse.
I've done such inspections. Sometimes I can specify the problem, other times its a matter of just documenting a bunch of various problems.
Attic furnace there's bound to be a bunch of issues.

[Eric Barker]

I have heard of this. If the attic is poorly ventilated then you can't use it for a furnace's combustion air source.

[Tom Rees]

Mathew, Was the attic vented? I use the 1-1000 rule, 1 square inch of vent for each 1000 btu's. 80,000 btu furnace 80 sq. inch vent-8"x10".

[Larry Morrison]

Where I am, they require a dedicated vent for the gas furnace through the roof. I think this probably came about because the newer designs of homes lack proper ventilation (1sf/300sf of living space) The gas supplier wants to make sure the appliance works regardless of the amount of attic ventilation.