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Getting Hammered About a Fireplace Call


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Hi All,

The following is a query sent to me via email by an inspector friend of mine in the area. Check it out. It sounds to me like this might be a Rumsford fireplace install but I've never heard of this kind of flue before. Perhaps one of you - Bill K. perhaps - can help shed some light on this for Mack.

Post your responses here and I'll direct him to follow this thread. Don't know if he'll participate; not sure he likes all of this online tomfoolery.

ONE TEAM - ONE FIGHT!!!

Mike

Hey Guys:

Got some egg on my face on this fireplace call and am trying to get more information- maybe fill in some gaps in my knowledge.

Check out these photos:

The camera was in the fire box looking up, placed on top of the gas log appliance.

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The top of the flue under the chimney top damper

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The exterior of the chimney looked like this:

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When Cullen (Cullen is Mack's son. He works for his father's company.) showed me the pics from inside the fireplace, I had a hard time believing what I was seeing. So I checked with a chimney company and a masonry company that builds fireplaces, and they agreed with my first impression, that ? in addition to some weirdness and deficiencies, the top of the fireplace was missing.

I included that in the report. The poop hit the fan. The whole thing has been inspected by a third chimney company and found to be fine.

The explanation is thus:

There is apparently a ?new? design (much like that used 300 years ago?). The firebox is essentially open to the sky (but with a chimney top damper). The new twist is that there is a secondary (unlined) flue chamber that ties into the primary flue at the top and bottom of the structure. This somehow creates a better draft and better burning. So I am left with these design and deficiency questions:

Design:

1. I see no provision to prevent backdrafting. There is a straight shot from the top of the chimney down into the firebox. There is no smoke shelf to help roll a backdraft back up the flue. What on earth keeps this thing from backdrafting smoke or soot back into the house?

2. Why doesn?t the secondary flue have to be lined [iRC R1001.8]? As rough as the parging is, it will collect creosote and soot much faster than the lined chimney. How are the nooks and crannies of the secondary flue going to be cleaned, especially those areas formed by the tile corners (note red arrows)?

3. Why doesn?t the firebox have to be airtight below the flue (see circled area)? All of my fireplace training has been pretty consistent that the firebox be pretty much air tight so that hot gasses, smoke & embers cannot escape ? except up the flue. Pyrolysis and all that. Is this no longer the case?

We had numerous requests in for drawings of THIS structure; they kept sending drawings of ?typical? structures. We were supposed to have a meeting tonight with the builder and the Muni but then I got copied on the inspection report from the chimney expert and was thanked for my services. I am, of course, a little irritated at this point. I know there is some flakery here, but would like a bigger hammer before I re-open an issue my client regards as closed. I did send a request for clarification to the Gumby that blessed this thing. I can find nothing on line about this new design, codewise or otherwise. I did find one drawing of a chimney constructed with a chimney-top damper but it had only one flue. I am really baffled here about the efficacy of the secondary flue. I appreciate your time and effort; thanks.

Hearing from anybody with experience or information with this design would be greatly appreciated.

MacK

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Hard to tell the whole story but from what I can see, the flue is not sealed to the smoke chamber or supported on all four sides. The flue must be sized per the code to the fireplace opening. You cannot use the space around a flue liner for venting anything else. Look for a F.I.R.E. Certified Inspector

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. . . There is apparently a ?new? design (much like that used 300 years ago?). The firebox is essentially open to the sky (but with a chimney top damper). The new twist is that there is a secondary (unlined) flue chamber that ties into the primary flue at the top and bottom of the structure. This somehow creates a better draft and better burning. . . .

Someone's playing you.

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This set-up has nothing to do with Ben Thompson's (Count of Rumford) fireplace design. His throat design was the first to include a smoke shelf. This has nothing to do with any fireplace or chimney system design of centuries ago.

In addition to the improper throat and smoke chamber not sealed to the flue liner, using the space around the flue liner for combustion air is not acceptable, the flue liner is required to terminate above the walls of the chimney and brick ties are not adequate for supporting a terra cotta liner of any height.

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