Jim Baird Posted May 11, 2020 Report Share Posted May 11, 2020 A gas fired water heater stands in a house's utility room that holds about 60% of the 50 cf per 1K BTU needed to meet code. The room does have a central HVAC supply duct. Does that supply duct negate the room as "confined space"? Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted May 11, 2020 Report Share Posted May 11, 2020 4 hours ago, Jim Baird said: A gas fired water heater stands in a house's utility room that holds about 60% of the 50 cf per 1K BTU needed to meet code. The room does have a central HVAC supply duct. Does that supply duct negate the room as "confined space"? Not per the IRC. The City of Portland used to have a citywide exception that allowed a supply duct to serve as a combustion air opening if it was big enough to do so when the HVAC blower was not running. The upshot is that the duct is never big enough. (It makes no sense to have a huge supply duct going to a small utility room - and a large utility room wouldn't need the added combustion air in the first place.) Quote Link to comment Share on other sites More sharing options...
Jim Baird Posted May 11, 2020 Author Report Share Posted May 11, 2020 (edited) Thanks for the reply. This room is about 1100 cf but 34K water heater wants 1700. My wag at duct size is 8", which would take 142' length to make enough volume, but the supply system does size up as you approach the equipment, so I am thinking a louvered door might be the best approach. Gas water heaters are not very common around here. Edited May 11, 2020 by Jim Baird Quote Link to comment Share on other sites More sharing options...
Erby Posted May 11, 2020 Report Share Posted May 11, 2020 A high and low vent from the attic would also suffice. Quote Link to comment Share on other sites More sharing options...
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