New house–Air intake vent is about 4-ft below high efficiency furnace & water heater exhaust vents. Dangerous?
Recently bought a house that has natural gas furnace w/ 95% AFUE, a natural gas Rinnai tankless water heater w/ UEF 0.92, and a Fantech FG8 air intake (which I believe may operate at around 300-400 cfm).
Attached pics show the intake of the Fantech (white hood near ground) is about 3.5-feet beneath the exhaust of the concentric Rinnai vent (black), and about 4-feet diagonally beneath the concentric furnace vent (white).
My understanding is that ASHRAE recommends 15 feet of distance from an air intake to a combustion appliance vent.
Is this 3.5 to 4 feet of distance at my house dangerous such that I should disable the Fantech until I’ve moved its intake further away from the furnace and Rinnai?
Or is this setup adequately safe that I could allow the Fantech to run 15 minutes per hour for a few weeks until I have time to move its intake further from the furnace and Rinnai?
Thanks for any input!
P.S. I think ASHRAE also recommends that intake vents be 2 feet above grade. Mine is more like 6-8″. When I move it, I’ll plan to fix that problem as well.
P.P.S. For what it’s worth, this was permitted and inspected (apparently passed) by the local AHJ, and installed by a fairly reputable HVAC company in the area.
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