Miller mobile home furnace soot in exhaust chamber but not burn chamber

cabinover

Hi all, not an HVAC tech but do work for an LP company in VT. Wondering if any of you can tell me how this can happen. I moved my furnace this past weekend to do some work below it and remove an A-coil. The exhaust pipe had a good amount of soot in it. Looking at the top of the heat exchanger it also had soot, about 1/8" thick. Removed the orifice tube and all looks new (unit is 14 years old but probably has less than 5 years run time, have a coal boiler also). Removed the burner assy and the first 1/2" closest to the outside is sooted, the rest is like new as is the burn chamber.

I've been told it's probably leaking at a gasket...ok, I'll bite. Does this make sense? I don't understand how it could possibly soot up after the burn chamber area if that area is virgin white like it's brand new.

Appreciate your thoughts on this if you've seen it before. My lead techs recommendation is to pull the front panels off and install new gaskets. It's entirely possible this problem has been there since it was newly installed in 2008.

Thanks!

pecmsg

Combustion Analyzer #’s?

Jamie Hall

Soot will not accumulate in areas which are very close to or impinged on by active flame. I'd check and make sure you don't have impingement and are not over firing it.