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High stack temps

Kjmass1 Member Posts: 223
I had MassSave out for an energy audit and they did a combustion analysis on my 35+ Penco 200K Steam boiler. They said it was operating safely but mentioned the exhaust temps were over 500F...what does this mean? Anything to be concerned with?

Boiler is serviced yearly by someone from this board.


  • Grallert
    Grallert Member Posts: 587
    That's bit high. Depending on what else is going on combustion wise I wouldn't worry too much. If I was servicing that boiler I'd try and find out why is that high. Did you get any more numbers from MassSave?
  • Steamhead
    Steamhead Member Posts: 16,272
    edited February 2019
    I'd check to see if the burner is over-fired. If it isn't, there may not be much you can do- some of these older boilers were pretty inefficient.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    EBEBRATT-Ed Member Posts: 13,834
    Depends. I wouldn't consider 500 really excessive. I would consider 600 excessive. Next time it's serviced I would check the combustion efficiency and firing rate. Doesn't sound like a serious issue.

    Is this gas or oil?
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,261
    Could also be too much draft.
    EBEBRATT-Ed Member Posts: 13,834
    Gas with a draft diverter draft probably not an issue but oil it certainly could be an issue. Combustion test
  • Kjmass1
    Kjmass1 Member Posts: 223
    I’ll see if I can get the combustion numbers when he emails me tonight.

    It is natural gas. Actually 1970 so quite old.

    He was testing it at worst case draft scenario, baths fans exhausting, dryer, and large Pro range hood on max.

    My guy who serviced it in the fall did mention he tweaked the firing.
    HVACNUT Member Posts: 5,261
    Is that gross or net?
    Nice job running all exhaust to check for back draft but did he calculate the free air needed for proper combustion?
  • Kjmass1
    Kjmass1 Member Posts: 223
    Not sure, he just mentioned it offhand.

    That is gross 199k/152k.

    My sticker from servicing says 8.6 O2 with 495F stack temp so I guess that’s how he wanted it set up.
    EBEBRATT-Ed Member Posts: 13,834
    Those are good #s for gas. Not the best if it's oil. We still don't know do we??

    If it's gas your ok
    EBEBRATT-Ed Member Posts: 13,834
    If the CO is ok
  • Kjmass1
    Kjmass1 Member Posts: 223
    It’s gas. He said CO2 passed fine. Sounds like I’m all set. Thanks!