Category III flue–clearances, etc.
I’m about to install a Takagi flash water heater and am trying to order the correct flue parts. The unit requires stainless steel flue and the dealer I’m using sells ProTech/FasNSeal parts. There is single wall and double wall, and I want to use single if possible.
The heater will be wall mounted on an interior wall and will vent straight up thru the ceiling, into the attic, and up thru the roof, with no bends. Total height of the stack including everything will be about 7.5 feet.
According to Code Check, both the UMC and IRC read something to the effect of ‘single-wall may not pass thru floor or wall’. Now, technically, I want it to pass thru the ceiling and then the roof.
Anyone have direct knowledge of this application? I need to know the clearances to the pipe as it passes thru the ceiling and roof, and also to the wall behind the heater (that clearance is governed by the exhaust port on the heater…)
Replies
You'll have to use double wall - single wall requires 6" clearance from any combustrible and cannot pass through a wall, ceiling, floor, (in the words of one of the great code inspectos, "One man's ceiling is another man's floor {G}), roof OR attic space.
Bit the bullet and pay a little bit more. There is no good reason to stick with single wall other than being cheap; and in the long run the double wall is far less likely to have internal condensation and corrrosive drainback into the unit.
And don't forget to plan for adequate clearnace above the roof; as a general rule clearance depends on roof slope and the proximaty of any vertical surfaces within 8 feet.
"It is as hard for the good to suspect evil, as it is for the bad to suspect good."
-- Marcus Tullius Cicero, statesman, orator, writer (106-43 BCE)
Bob is right, ya gotta have Double wall SS. that has a 1" clearance to combustibles.
For woodburners ( hotter flue temps I believe) I use single wall in the heated area, a double wall from there up. You may also need a supportbox for the cieling pass through, a flashing cone and storm collar.
If the outlet on the back of the appliance is configured right you will be using double wall in the condintioned area as well..pricy stuff...I know, I'm looking at 16' of it and 16+ of single wall.
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