Gas Fired Furnace Help

1960’s home. The gas fired water heater (1985 install) and newer furnance install (2005) are in the same hall closet with not exterior combustion air supply.

  1. Is the clearance to the wall adequate? Less then one inch in this case and what constitutes a “protected wall”? Drywall?
  2. Would you recommend relocation for the gas fired water heater or adding outside combustion air?
  3. Should the bypass doors for this location be replaced with a tight closing, weather stripped door?
  4. Any other recommendation by you HVAC experts is welcome!! Thanks!


Peter Your question is not cut and dry most MFG set the clearance requirements for the furnace not the local ordnances so I am not much help in that area. As for the combustion air, our requirements might not be the same as yours but a 2005 furnace closet should have been installed with an outside combustion air provided. We use the two pipe system one high and one low into the closet from the attic and is a requirement for an enclosed closet.

In this state a gas fired water heater and a furnace can be located within the same closet and usually are, either in the garage or within the home but the combustion air must be sized for each unit combined.



I’m with Charley, lots of variables here, but…

  1. typical clearances on sides and rear of furnace (by MFG.) is 1" and clearance on front varies with installation location, but access to service the unit typically requires a min. of 18", and someone my size would need 36".
  2. I would’nt recommend relocating the Furnace or WH unless I could’nt correct the clearance(s) problem and/or could’nt add the required combustion air to the space, to Nat.,St.,Local std’s.
    3)I’d recommend installing Louvered doors, but that’s just me.
    4)I’d recommend removing or shortening the wood shelf that appears to be almost touching the flue vent and relocating all those stored paper products.
    I’m guessing there are other questions you have about this installation, based on your questions, but the picture does’nt show me much else to comment on.
    Good Luck

Don’t forget the TPR extension on the water heater.

Thanks Charley Creg & Larry I’ve pretty much knew what I wanted to say or recommend, I just needed some input, thoughts from you guys. I appreciate it,… and thanks Larry for the heads up on the TPRV tube, there is actually one installed that is going down the side of the unit, the pic angle makes it seem like there isnt one, but good catch.

In addition to what was posted above. Where is return air being pulled from on this unit (hopefully not from within same space)? Outside air is good recommendation.

Need min of 6 in. clearance on the single wall vent (looks like first 8 in or so of flue material). Looks to terminate into double wall B-vent above that? min 1 in clearance). If not terminate, the single wall requirement intact for full run of vent flue.