Originally Posted By: rsummers This post was automatically imported from our archived forum.
Couldnt find any resent posts so here is one. You need 1 sq" of area for every 1000 BTU"S of fule input. So a 100,000 btu furnace would need at least (2) 4x14 openings placed with in 1st (12") of the floor and ceiling. One high and one low. I always make it a point to make sure that they are not covered up or clogged with dirt during an inspection.
Originally Posted By: rsummers This post was automatically imported from our archived forum.
Well I guess you couldn’t say there is a standard opening size but 4x14 and 6x14 is what I typically see. You would have to know the combined BTU of all the appliances in the mechanical room to know what is really needed.
Originally Posted By: ebabcock This post was automatically imported from our archived forum.
I see gas water heaters and furnaces in unfinished garages without openings to the outside for ventilation. Is this OK because the garage is unfinished and there is enough air infiltrating into the room?
Originally Posted By: ebabcock This post was automatically imported from our archived forum.
I should have been more specific with my question.
I wasn't referring to flue pipe venting. I'm referring to having air vents for combustion air. In an unfinished garage, does a gas water heater/furnace need a disignated opening in the door/wall for combustion air ventilation?
Originally Posted By: Blaine Wiley This post was automatically imported from our archived forum.
A gas burning appliance requires 50 cubic feet of air space per 1000 BTU’s. If the water heater is an average 40,000 BTU unit, you would need about 250 sq. ft. if the ceiling is 8’ high. Garage doors seldom seal air out very well, but many localities are requiring outside combustion vents within x number of feet of the unit(s). I would recommend you find out what your local requirements are.
Originally Posted By: rcloyd This post was automatically imported from our archived forum.
Also, it is extremely important to make sure that all sources of ignition are at least 18 inches above the floor. This must be done to prevent igniting of vehicle fuel fumes that are heavier than air and travel along the floor. Make sure the appliances are protected from vehicular impact as well.
Originally Posted By: rsummers This post was automatically imported from our archived forum.
Great question Eric I will have to open the code book for that one I have seen many furnaces & water heaters in garages with out Vents to the out side. I know that in commercial Buildings with Mechanical Rooms You size the combustion air for the btus of all appliances in the room.