New construction, s.f. detached home, substantially complete
40,000 BTU gas-fired FVIR-type water heater & 88,000 BTU 80% efficient gas-fired furnace installed side-by-side in 110 cu. ft closet, 20" off garage floor.
This gives you 128,000 Btu per hour combustion air requirement., Yes according the Peoples Energy of Chicago the room in which the appliances are located are what you consider the “room” in which calculations for confined spaces are made.
Closet is located off-of and accessed-from a typically-sized 2 car garage, roll-up metal door, with no access or air communication from the closet to the home’s interior spaces beyond the firewall.
Closet is accessed by a pair of bi-fold type doors, solid type. When closed, bi-fold doors provide 23 sq. inches of visible gap at the door bottom, and 46 inches of clear, visible gap at the door top. Net openings are 69", with no other openings in the closet (either at the closet floor to the crawl, or at the closet ceiling to the attic spaces).
Can you clarify this ? Are these completely solid bi-fold doors? Are they “cut” on the top and bottom to allow for “air” gaps? Remember you need 1 square inch for every 1000 Btu’s combustion air. (best practice is to have one high vent and one low vent with in 12 inches of top and bottom) The Garage is the adjacent room that will be supplying combustion air for that “closet”. Now comes the next factor : Is the garage "large enough " for supplying combustion air and can that air be exchanged (considering sealed room with little exchange of air)?
You can get an idea of "confined space by using calc. H’x W’ x L’ x 20 for confined space figure based on 132,000 Btu’s for cut off point minimum before it turns into confined space.
By definition, the closet is clearly a confined space. Questions:
1.) Is the garage also considered a confined space?
No, since closet is first consideration with respect of confined space. Yet the adjacent room is also a gray area since that “could also be to small” so a high and low vent duct from the exterior or attic is one answer for this. You can always check the MFG instructions for best practices with regard to any appliance install. That is the number 1 place to check!
2.) The garage is clearly the only obvious source for combustion air availability (other than whatever air exists inside the 110 cu/ft utility closet). Do I consider the garage an “OUTSIDE” combustion air source?
Adjacent room , Yes
3.) Even if the garage suffices as an “OUTSIDE” combustion air source, does the 69" of available openings at the utility closet door represent an unacceptable restriction of available combustion air, given the input capacity of the installed appliances?
One way you can look at this if you consider 1 sq inch for every 1000 Btu’s but another goofy thing is that you have a FVIR WH but the FAU can ignite any flammable vapors… So figure that one out?? $$$$$ is always before common sense… I also have a guide if you want it from my local utility regarding a lot of what you are asking here. Just drop me a note if you want a copy. Homeiguy@sbcglobal.net
Thanks in advance for your opinion(s)