What would be the fresh air intake requirements for a 36,000 BTU
natural gas water heater?
I used to have a 72,000 BTU 80% natural gas furnace, and a 36,000 BTU
natural gas water heater. The fresh air intake for both was provided
by a vent (i.e. hole) in my basement wall in the furnace room to the
I've since upgraded my furnace to a 93% efficiency model, so its fresh
air intake is supplied by a PVC pipe that runs outside through the
concrete foundation (through a new hole).
So I'm wondering (hoping) whether I can make the original vent smaller,
as it now only serves the water heater, and all the cold air coming in
from the outside is wasting energy needlessly.
The furnace installer (who was pretty junior as he was young and
screwed a couple of things up and I had to call the company back to fix
the problems with an older repair man) had said to leave the original
vent alone. But I would think that the water heater (36,000 BTU) could
suffice with a smaller fresh air intake vent than what was originally
done to serve both the water heater and the furnace? Assuming the vent
size is related to the BTU capacity, the gas water heater represents
1/3 of the original setup (36,000+72,000).