gas water heater location - InspectionNews

wes owens · #1 (**permalink**) 04-28-2007, 11:31 PM

I found a 15 year 0ld "A.O. Smith" gas water heater in a hall closet, and the only available air was from the 1/2 inch gap under the door.

I wrote it up as needing vents added to the door per manufactures specifications, but wanted to make sure I was correct in doing this.

Jim Luttrall · #2 (**permalink**) 04-28-2007, 11:39 PM

Yep
Was the shelf too close to the flue?
Probably needs to be removed anyway.
Jim

#3 (**permalink**) 04-28-2007, 11:51 PM

Wes,

From the 03 IRC:

M1702.2 Confined space.
Where the space in which the appliance is located does not meet the criterion specified in Section M1702.1, two permanent openings to adjacent spaces shall be provided so that the combined volume of all spaces meets the criterion. One opening shall be within 12 inches (305 mm) of the top and one within 12 inches (305 mm) of the bottom of the space, as illustrated in Figure M1702.2. Each opening shall have a free area equal to a minimum of 1 square inch per 1,000 Btu/h (2.20 mm2/W) input rating of all appliances installed within the space, but not less than100 square inches (0.064 m2).

John Arnold · #4 (**permalink**) 04-29-2007, 06:00 AM

Absolutely. That's a CO generator: not enough air for proper drafting up the vent - exhaust CO2 builds up in the closet while oxygen is depleted - CO production is underway.

Richard Rushing · #5 (**permalink**) 04-29-2007, 08:10 AM

Most all closets will be a confined space.

For the room to NOT be considered a confined space, you take the total INPUT BTU'S and divide by 20 (Example; 50,000 btu/ 20 = 2500 cubic feet of space). I used 50,000 btus as an example only-- most 50 gallon w/h's are approx. 40,000 input btu.

2500 would equal the (bottom) number in cubic feet of space in the room required to NOT BE a "confined space", any smaller than that and the "confined space" requirements are in effect.

Since most w/h closets are approximately 3 x 3 x 8, that would only equal 72 cubic feet. That's a far cry (72) from the 2000 Cu Ft. needed to not be a confined space for a 40,000 but w/h.

Since the confined space requirements are in effect, that means that indoor air openings shall have two openings minimum, each must meet the following:

one square inch per 1,000 Btu opening size
100 square inches (minimum) in size
not less than 3 inches in its smallest dimension
one opening within 12 inches of the ceiling
one opening within 12 of the floor

Now, if there are multiple gas applinaces in a closet (such as a water heater and a gas heater unit) you do the same thing as above, but combine the total btu's and divide by 20 to get the minimum cubic footage requirements for that to be considered a 'confined space'.

Richard

wes owens · #6 (**permalink**) 04-29-2007, 10:52 AM

Thanks guys.