Wall Thimble for Generator Exhaust

Sun Dog
Sun Dog Solar Expert Posts: 115 ✭✭
in Off Grid Solar & Battery Systems #1
Anyone know where I can source a good wall thimble to run my generator's exhaust through? Pretty sure the exhaust itself will be ~2" diameter and the wall, including the siding is 9" thick.
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,022 ✭✭✭✭
    #2
    Re: Wall Thimble for Generator Exhaust

    How about a through the wall thimble for a wood stove. It will be a short piece of insulated chimney pipe suitable for the high temp of the exhaust pipe passing through it.

    Ralph
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: Wall Thimble for Generator Exhaust

    More of discussion than an answer:

    http://forums.mikeholt.com/showthread.php/117439-Generator-Wall-or-Exhaust-Thimble

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #4
    Re: Wall Thimble for Generator Exhaust

    Rn it through. A piece of "B" vent, a touch bigger than the diameter of the exhaust. "B" vent is cheap, and is 1" to combustible,all and ceiling/roof thimbles are easy to get.

    T
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  • Sun Dog
    Sun Dog Solar Expert Posts: 115 ✭✭
    #5
    Re: Wall Thimble for Generator Exhaust

    Tony, is B vent that double wall stuff used to vent propane space heaters etc? If yes, would you just use it as is or would you fill the air gap between the two walls with some kind of non-flammable insulalting material? Ralph, I have seen examples of what you suggested but they mostly seem to accomodate a 6" pipe and I'm not sure what the best thing would be to neck them down. At -45C I don't want any big air gaps.

    Steve
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,022 ✭✭✭✭
    #6
    Re: Wall Thimble for Generator Exhaust

    Steve,

    If it's just a generator shed you'll be needing fresh combustion air anyway...

    I have a fresh air opening about 12x24inches, and a barn fan to help draw the heat away. Is the exhaust thimble for a wall or ceiling?

    Ralph
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #7
    Re: Wall Thimble for Generator Exhaust

    B vent is double wall pipe(aluminum). Stuff the outside of the pipe when it goes through the wall with fire safe rock wool. If y ou leave a bit if air space around the engine exhaust, I can't imagine that it would get hot enough to cause trouble. Test I t to find out,

    T
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  • Sun Dog
    Sun Dog Solar Expert Posts: 115 ✭✭
    #8
    Re: Wall Thimble for Generator Exhaust

    Ralph, yes it is for the generator shed. It will have a 30" x 30" motorized intake louver and a 24" x 24" motorized exhaust louver. My plan is to run the exhaust out of the wall. If there is enough leakage in the building I may just open the exhaust louver in the dead of winter, time will tell.

    Tony, is Roxul just a brand of rock wool insulation or is it completely different stuff?
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