Combustion Air Minimums

Originally Posted By: anatol polillo
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Fellow Inspectors,


Had a townhouse today. Utility closet, non-louvered doors. In the ceiling, there is a 5" air inlet from the attic that terminates at the ceiling. 50,000 btu input gas fired furnace and gas fired water heater in closet.


"A ventilation air inlet grille located in the wall or door, level with or below (D) the combustion air inlet to the lowest burner. The area of the grille must provide 1 square inch for every 2,000 Btus per hour of natural gas input to gas equipment in the area."

By my calculations a 50,000btu input furnace will require a minimum of 25 sq in. The vent provided will only provide 19 sq in. This is not enough for the furnace and water heater combined.

Is my assumption of 1 sq in per 2,000 btu correct?
The gas was off, so I was not able to fire the furnace or water heater.
Anatol


Originally Posted By: scieslewicz
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Anatol,


Your scenario depends on the manufacturer's specifications. Was there not an opening from the closet to the adjacent area (high and low openings)? Besides the attic opening, the size of the closet may have been figured into the calculation as well.

Sue


Originally Posted By: anatol polillo
This post was automatically imported from our archived forum.



Sue,


There were no other openings in the closet.


Anatol


Originally Posted By: phinsperger
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1 square inch per 2000 BTU (split into upper and lower vents) is if the unit is drawing internal or if the draw from outside is horizontal


1 square inch per 5000 BTU if the unit is drawing from external which it sounds like this one is. Be sure the attic is properly vented as well


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Paul Hinsperger
Hinsperger Inspection Services
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Originally Posted By: anatol polillo
This post was automatically imported from our archived forum.



Thanks all…