smoke in the Great Room

[Brian Schreiber]

Smoke in my Great room. Newer home, 5 yrs old, Accucraft fireplace insert into 14" Class A, insulation packed dual wall flue pipes. 4 ft long, stacked on each other. Two sided FP doors, not leaking at the doors. Got a fire alarm today, and lots of smoke on Great room side of FP-- only up high at about 12ft near cathedral ceiling.
The flue pipes are enclosed inside a masonry sheathed 2x4 chase.
No smoke on other side of FP(bedroom) and no masonry sheathing there-- sheetrock wall above FP doors. My conclusion is that the chase enclosing the flue is building up with smoke and it finally is released at a crack in the mortar near cathedral ceiling. . .

Question: the ONLY place I can figure this could leak is at the tiny clearance area around the throat damper shaft for the flue. However, it is hard to believe that tiny exit spot could allow so much smoke out that it could be "seen" and sensed by the fire alarm. . . Hard to believe also that the dual lined FP flue could be leaking-- at their tight joints for example.

Whatever the case, The FP was really hot(door glass was over 550°F, I have a thermocouple meter and checked it). I have run the FP this hot before and not had this problem. . . At least not enough where I could "see" smoke and certainly not enough to cause the fire alarm to go off. I checked up in attic where the dual FP flue is sealed to attic floor-- it was warm but all was OK no evidence of overheating or anything.

So, wondering if you have any thoughts on this and if you agree that the clearance one the flue damper shaft is the only possible place of exit?

Appreciate any thoughts or suggestions you may offer. thanks for your time!

 

[begreen]

Something is wrong for sure. There should be no smoke. It needs to be inspected to verify nothing serious is amock in the chase. This is just speculating without seeing inside the chase. Is it possible that when it was installed they used paper covered fiberglass batts of insulation? If not well secured, one may have broken loose and come in contact with the chimney.

 

[Brian Schreiber]

no, at the point where the flue transitions from the Room ceiling into the attic there is another large diameter, galvanized tube with creating an annular opening filled with air separating the Class 2 flue from any wood / flammable materials.

I guess you are at a loss also as to if there could be any other "hole" as such that would allow exhaust gases, it appears. It sounds like you are leaning towards something in construction materials being burned rather the possibility of exhaust gases exiting. . . ?

 

[Brian Schreiber]

Something is wrong for sure. There should be no smoke. It needs to be inspected to verify nothing serious is amock in the chase. This is just speculating without seeing inside the chase. Is it possible that when it was installed they used paper covered fiberglass batts of insulation? If not well secured, one may have broken loose and come in contact with the chimney.

can you suggest a means of inspecting inside the chase to minimize having to open it up much. . . ie deconstructing the masonry laminate. . .?

 

[begreen]

Truth is there could be more than one reason and anything here would be speculation. The concern is with the temperature link. Normally a chimney pipe won't leak just because the fireplace is hot, but anything is possible if the installation was poor or there is a defective pipe. If not the chimney, then pyrolysis is a possible and serious concern. This could also be sawdust on the top of the fireplace left over from construction when they sealed it up or clearance that are too close. I haven't located the manual for this ZC fireplace.

I think you will need to find a way of at least getting a camera with a light into the chase for inspection. A rigid or semi-rigid boroscope with a long focus range would help reduce the inspection hole size.
Amazon product ASIN B07HVT2XZLAnother option would be to cut a hole in the appropriate area between the framing studs. This could have a permanent inspection door installed or patched and rebricked.

 

[Brian Schreiber]

thanks, good suggestion. Being able to actually look in there without excessive deconstruction SURELY would be useful. I take it from your mention of pyrolysis the implication is a slow degradation and smoldering of wood or similar construction materials, right?

I personally installed the FP insert and the chimney and did so, to the best of my ability and knowledge, in the correct way. I surely did not leave sawdust etc on top of the unit. However, while running this hot on the doors(550°F measured) surely the flue is much hotter than that and so it is radiating that out-- reduced considerably though by the double lining and the filled fiberglas annular space between the liners. Peace of mind it seems will only come via direct inspection and hopefully that may be possible using the probe suggested. The only other thing I can conceive is the FP glass door seals and the annular opening around the damper shaft. . .