Simon, the door is not sealed, so it is still too close, no?
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Depends whom you ask 
The idea of that 10ft rule is not to depressurize the combustion air intake of the appliance, but there appears to be plenty of air from the top of the attic. It’s not in the code, so it’s hard to call it out if you really wanted to get picky. The fact that it’s “behind a solid door” does not make the 10ft rule apply, if you ask me. The code does not specifically address this, so you would have to ask the AHJ or the HVAC to see how they felt on that day This is one of those “gray” areas.
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Manual doesn’t require it. They only say to refer to local code for gas install
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I would call it out for enhanced safety…it is a pretty big gap at the bottom of the door. JMHO…YMMV
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I would call it out.
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Doesn’t it require a certain number of cubic feet of fresh air for combustion? Are you saying that the closet ceiling gap is enough to provide that?
The cubic feet of space is for when combustion air is taken from the indoors. Because the ceiling is open, the combustion air comes from the outdoors through the attic’s ventilation. Need 1sqin of duct air intake for every 3000BTU, I mentioned this above.
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I see. Thanks Simon
I don’t have a problem with the closet being better sealed It just may not be a requirement by HVAC tech is all, so the way the comment is worded is important. Too many times the tech comes out and throws the inspector under the bus and I try to avoid that.
This is the actual code that governs the 10-ft rule:
M1602.2 Return Air Openings
[Return air] openings for heating, [ventilation] and [air-conditioning systems] shall comply with all of the following:
- Openings shall not be located less than 10 feet (3048 mm) measured in any direction from an open combustion chamber or [draft hood] of another [appliance] located in the same room or space.
So is it in the “same room or space”, you tell me, I can easily argue it is not in the same space or room because it’s behind a door.
I’m not stating code, I’m stating potential safety.
They can do it or not.
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Just a follow-up. This is what I provided to the client based on combined recommendations from you folks. Thank you for your help and for giving me an opportunity to learn from the best. I appreciate each of you.
“The requirements for combustion air may be met when considering the attic opening in the HVAC closet ceiling, however the closet is not sealed off from the living space and the return air vent is within 10 ft. of the furnace. Recommend evaluation of gas fired furnace installation in unfinished closet by an HVAC professional for enhanced safety and functionality.”
Along with the smoking gun (drip leg) - they will get an HVAC pro to come out and give a look. He may call me an idiot, but I feel I did the right thing by identifying.
Thanks again TEAM!
I also see a problem with it! I would think that this opening to the attic would need a proper and effective draft stop/fire stop. Just as any open chase from a living space into an attic. Also I’m guessing that door and those walls are not insulated which would also be a source of energy loss.
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Proper and effective? What good would a fireblocking or draftstopping do? you would still have a hole in the ceiling:
IFGC 304.6.2 One-Permanent-Opening Method
One permanent opening, commencing within 12 inches (305 mm) of the top of the enclosure, shall be provided. The [appliance] shall have [clearances] of not less than 1 inch (25 mm) from the sides and back and 6 inches (152 mm) from the front of the [appliance] The opening shall directly communicate with the outdoors, or through a vertical or horizontal duct, to the outdoors or spaces that freely communicate with the outdoors (see [Figure 304.6.2]) and shall have a minimum free area of 1 square inch per 3,000 Btu/h (734 mm2/kW) of the total input rating of all [appliances] located in the enclosure and not less than the sum of the areas of all [vent] connectors in the space.
Do you recommend fireblocking and draftstopping for whole-house fan that dumps into vented attic?
It’s complicated, boss! The gas appliance manufacturer wants me to follow the latest NFPA 54. Well, it says it has to be 3inches, but IRC steals it from IFGC and says any length is mighty fine. Well, you tell me! 
I think the fellows at IFGC (ICC) got pissed @ NFPA crew and decided to mess with them. If the installer is not a cook subbing for a plumber/heating contractor, he would make it at least 3in, that’s my 2 cents.
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The manufacturers installation instructions almost always state “follow local building codes”.
I’ve taken many many old sediment traps apart. You know what I find in them…zip.
I always recommend when posts like this come to the forum to just contact a local plumbing contractor.