Thread: Furnace exhaust flue clearance

Manufactured home, Coleman gas furnace and American gas water heater. Both units have this flue installation. In the picture it's a bit difficult to tell but that square piece screwed to the sheet rock is a thin hard wafer of some sort. It does not appear to be metal. At least with the metal collars sometimes you can pull them down a bit to check for the 1" clearance to combustibles.

So I guess my question is what is that wafer made from and why is anything other than metal, including sealants which can be fire resistant but not fireproof, allowed to be in contact with the flue. I see this in manufactured homes a lot in my area. Thanks, this is my first post.

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No picture.

Sorry, first post. Will try again.

Originally Posted by Geoff Stewart

Sorry, first post. Will try again.

What a hack job on the sealant. Even the screws and staples are placed irregularly. It appears like a DIY'r add on after the fact, not the sort of work you'd expect to see coming out of a pre-fab place,

It is hard to see in the picture but could it be cement board, the type used as an under-layment for tile?

Yeah, that's what I thought, cement board. But I see it so often in manufactured homes around here that I'm thinking that it's probably not a DIY'r thing. Probably the HVAC guys or other contractor. Thanks.

Fuel-fired HVAC and water heating equipment used in manufactured or "mobile" homes must be specifically listed for installations in same. Installing and the use of such equipment must be done following the instructions for same.

It is beyond unwise to do otherwise.

What has been described and photographed, as represented, would be hazardous and dangerous, along with its associated Civil and possibly Criminal liability mine-field.

Thanks to all who replied. I now have a different view in terms of how I report this condition in the future.

Beyond the question of vent clearance to combustibles. As HG said, the furnace probably isn't listed for install in a manufactured home. In large part, it has to do with combustion/dilution air supply. Manufactured homes are constructed pretty tightly, which is why the Coleman furnaces and gas/propane water heaters are direct vent, pulling combustion air from outside.

.............take a look at the connection to the furnace. More than likely, you will find the actual 4" flue connection that runs up inside of that 10" pipe depicted in your photo. This is a typical HUD code manufactured home chimney assembly, and is supposed to be tightly finished at the ceiling. The large diameter pipe maintains the correct clearances without concern for distance to combustible surfaces. This is an especially sloppy job and should be noted as such-but as presented, poses no hazard.........Greg.