odd stack temp difference/

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mikeyny

Feeling the Heat
Nov 16, 2007
294
upstate ny
cleaned my boiler last nite, long overdue, stack temps were up, too much fly ash in the tubes and on the turbs. So i added another magnetic therm on the flue pipe. one about a foot from the back of the boiler on an elbo and one about 2 ft from that one on the corrugated stainless liner that come out of the masonry chimny. The second temp is 100 or more degrees higher. i switched therms and got the same result. 100 or more higher 2 ft further away.
heavy gauge pipe 8 inches off the boiler then 1 elbo (right hand turn) (first therm) then a transition into stainless T. Cleanout cap on bottom of tee and chimney liner( left turn) on other side of tee and 2 ft up into the chimny. is the temp diff because of different metals, stainless vrs steel or is it a matter of flue gas stalling at the tee and giving a hotter temp. normal stack temp when just cleaned at full burn ranges from 3 to 450 depending on wood quality. i have too much draft so i have all 8 turbs installed when i have good dry wood like this yr. with less dry wood i remove a few turbs accordingly. For an old tarm it is pretty efficient when using all of the turbs.
 
I've found that the magnetic therm's (which I do use) are impacted pretty heavily by drafts and close by exterior walls. Is your first thermometer getting a draft? Is it closer to a basement wall than the other one? Type of metal can certainly also impact it...
 
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