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Waiting for the condensate to return, or add new water?

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As part of the work the tech. did on our single pipe steam WMC EG-75 boiler today for our 5 unit building, he suggested we move the 10 minute delay for our probe low water cut-off to 2 minutes so the boiler doesn't go out on low water to keep it running & save 8 minutes of time. We think our condensate takes about 5 minutes to return per our test today, so were wondering if there's a downside to filling it up with some new water & having the condensate come back a few minutes later if it's technically extra water by then. Will there be a trade-off between too much water after condensate returns causing problems at the 2 minute delay setting, vs. the 10 minute setting letting 8 more minutes go by before firing up again but adding less new water?

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  • Jamie Hall
    Jamie Hall Member Posts: 23,322
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    There will indeed. If your time delay on feeding water is too short, you will wind up with the boiler overfilled -- which will cause all kinds of interesting mischief. About which your worthy tech. won't have a clue. Don't do it.

    Your boiler boils about half a gallon of water every minute -- so 2.5 gallons in 5 minutes. May I humbly suggest that you check and see if your wet returns, assuming you have them, are nice and open? And that all the mains and runouts are nicely pitched, so that the condensate doesn't linger in some dark corner?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Big Ed_4
    Big Ed_4 Member Posts: 2,785
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    Less water to boil less fuel it takes ..

    There was an error rendering this rich post.

  • dopey27177
    dopey27177 Member Posts: 887
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    Condensate lag is a problem.

    If you do not in effect have a problem with 10 minute firing delay to allow the condensate to return to the boiler do not change your set up.

    If you allow the change to a two minute delay and the auto feeder supplies water to the boiler you eventually will get a flooding condition. A boiler flooding condition will cause water to be pushed into the steam main which will cause banging and other problems.

    Jake
  • cubicacres
    cubicacres Member Posts: 358
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    Thanks, we're glad we stuck with our beliefs this time & didn't have him change it for us. Being inquisitive ametuers looking to optimize our building's steam system, it's hard to contradict professional techs in our area who always seem confident in their opinions about what to adjust, but turn out to be single-pipe steam knucleheads 2/3 of the time & don't consider the system operations as a whole :o
    I see the idea that not letting the burners stop from low water & waiting for condensate to return in a few minutes would normally be more efficient, but then too much water in the boiler when the condensate returns producing wet steam, water hammer, or other problems seems like it would negate any efficiencies of not interrupting the burners.

    We put the pressuretroll back down to around .5 psi cut-in from his raising it to 1.5 when he left. I think we'll attend the local community technical college steam & hot water 1 credit course when they offer it again next year for more background & comfort working on our own system.