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Combustion air for gas water heater

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[#1] Posted: 12/06/2006 - 11:58:49 AM
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Bradford-White 1993 40 gal gas water heater in a pantry closet with no air vents from which to pull combustion air. There are only a few inches to each side and front and 4-5' above the heater.

The IRC states (as clear as mud)

"Where the volume of the space in which fuel-burning appliances are installed is greater than 50 cubic feet per 1,000 Btu/h (4.83 L/W) of aggregate input rating in buildings of ordinary tightness, insofar as infiltration is concerned, normal infiltration shall be regarded as adequate to provide combustion air."

On one hand I like to think the proof is in the pudding, the water heater has been there since 1993 and everything seems to work fine. On the other hand my instincts tell me there needs to be some vents added. But pudding and instincts don't make for a fact based report.

My question is: what the hell is the IRC telling me and how do I calculate it? How do I determine the btu/h of this water heater? The data tag does not seem to tell me anything.

Attached is a pic of the data tag on the heater.

As always thanks


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Mark A. Perry
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Combustion air for gas water heater
[#2] Posted: 12/06/2006 - 12:28:18 PM
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BTU is on the tag, 34,000 / hr. room would have to be 32 x 50 cuft= 1600 cu.ft, 16x10x10. Big closet.
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Combustion air for gas water heater
[#3] Posted: 12/06/2006 - 12:36:58 PM
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Thanks a lot, I can't believe I looked right past the btu/h on the tag. Guess that does not make me today's bright and shining star.
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Combustion air for gas water heater
[#4] Posted: 12/06/2006 - 12:38:31 PM
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Your math is wrong.

It should be 34 X 50 = 1700 cubic feet and if it's less than that in volume you have to add additional venting.

The fact that it's been in there since 1993 and hasn't hurt anything only means that it's been installed wrong since 1993 and hasn't hurt anything, but still needs to be corrected.

OT - OF!!!

M.

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Combustion air for gas water heater
[#5] Posted: 12/06/2006 - 12:48:41 PM
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Sorry Mike, I was in a hurry. see Mark, if you just wait somebody less bright will show up.
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Combustion air for gas water heater
[#6] Posted: 12/06/2006 - 12:56:02 PM
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Quote:Originally posted by homnspector

Sorry Mike, I was in a hurry. see Mark, if you just wait somebody less bright will show up.
Yep,

My math skills are so poor it took me half an hour to do that multiplication. Do you have any idea how long it takes to lay out fifty rows of 34 paper clips each and then count them manually? Whew!

Phone kept ringing and I'd lose count, I sneezed once and ruined my calculations, I got mixed up and went "nineteen, twentyteen, twenty-one teen"......


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Combustion air for gas water heater
[#7] Posted: 12/06/2006 - 1:23:46 PM
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And for those who were wondering (like me) but were afraid to ask

(cubic feet) = (square feet) × (height in feet)

Mark A. Perry
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Combustion air for gas water heater
[#8] Posted: 12/06/2006 - 2:10:55 PM
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I had to take off both shoes, problem is I forgot I was missing a little toe :)
   
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