Fresh air intake requirements for a gas water heater?


J

jonny_rizzo

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
outside.

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).
 
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E

Edwin Pawlowski

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.
I lived in three houses with gas water heaters. They had no vents at all.
I see no reason it could not be reduced a bit.
 
S

SQLit

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
outside.

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).
Not knowing the exact situation, you need 1 sq inch per 10k btu of fresh
air, one air inlet high and one low.
Respond directly to me and I can send you the ~4 meg pdf file. That I have
or you can use google like I did
 
A

Andrew Duane

The installation manual for the heater should have pretty clear specs
on air intake. These things are calculated by the manufacturer, just so
the installer or homeowner doesn't have to "guess". Not that it stops
them from guessing anyway :)
 
H

Hell Toupee

What would be the fresh air intake requirements for a 36,000 BTU
natural gas water heater?
Check with your city or call your local energy company. In my city
fresh air intakes are only required for gas furnaces. Frankly, it's
not a bad idea at all to have one for the other gas appliances anyway,
to reduce the risk of backdrafts, but you're best off finding out what
is code in your area.

HellT
 
M

m Ransley

I dought you need an intake, it just cools the house, close it and check
for no flue draw, houses leak alot of air. Get a blower door test to
confirm it.
 
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S

Stretch

If the water heater is in the durnace room and the furnace room is
closed off from the rest of the basement ; the fresh air inlet may
still be required, depending on the size of the furnace room. You can
probably reduce it in size. I don't have my code books with me, but
SQLit may have all you need. Have him email it to you.

Stretch
 
J

jonny_rizzo

Hell said:
Check with your city or call your local energy company. In my city
fresh air intakes are only required for gas furnaces. Frankly, it's
not a bad idea at all to have one for the other gas appliances anyway,
to reduce the risk of backdrafts, but you're best off finding out what
is code in your area.

HellT
Thank you all for the replies. I'll call the energy company to confirm
whether it is needed or not (my hot water tank is a rental). Last
night I spoke to a few friends and family members living in relatively
new houses, and none of them had a vent specifically for their hot
water tanks, so it may not be needed at all.
 
D

DanG

You're sure not current on code.

(top posted for your convenience)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Keep the whole world singing . . . .
DanG (remove the sevens)
(e-mail address removed)
 
B

Bob

What code would that be?

DanG said:
You're sure not current on code.

(top posted for your convenience)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Keep the whole world singing . . . .
DanG (remove the sevens)
(e-mail address removed)
 
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D

DanG

Uniform plumbing code. Table 5-1

(top posted for your convenience)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Keep the whole world singing . . . .
DanG (remove the sevens)
(e-mail address removed)
 

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