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Boiler Overfilling

Steamhead Member Posts: 14,338
the water is probably leaving the boiler with the steam, which causes the feeder to kick in. A bad piping job is the most likely cause of this. Is the boiler piped according to the manufacturer's instructions?

If you don't have the manual for your boiler, you can get the info from the manufacturer.

How about posting a picture of the boiler so we can have a look?

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  • JArons
    JArons Member Posts: 1
    Boiler Overfilling

    I have a 1-pipe steam heating system with a McDonnell Miller low-water cut-off (#67) and Uni-Match water feeder. When the boiler was given its annual cleaning, the oil company's repairman said the water feeder was overfeeding the boiler, which I could see. He said there was too much dirt in the system (I flush it every week, but there is always rust--the radiators are probably about 75 years old). He also said the whole unit (cutoff & feeder) needed to be replaced if it continued to do this. He got the feeder to stop, but a day later the water level was at the top of the glass.
    My plumber cleaned out the cut-off (apparently the float had too much around it) and the problem seemed to abate--until I manually added more water to make sure the hot-water heating coil was submerged. A day later, I noticed the water level was again higher than it should be (glass went from 3/4 full to about 90% full), indicating that something triggered the water feeder to kick in, even though there was more water in the boiler, not less.
    My questions are: Isn't it normal to have a good deal of sediment in an old system like mine, and is there any way to fix this low-water cut-off, short of replacing the whole unit? Won't a new one just get gummed up like the old?
  • Mark Hunt
    Mark Hunt Member Posts: 4,909
    Have you

    actually witnessed the feeder coming on when it was not supposed to?

    It may be that water is getting by one of the valves and by-passing the feeder all together.

    Just a thought.

    Mark H

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  • Dale
    Dale Member Posts: 1,317
    Marks right

    The problem us usually a slow leak through the feeder, If the feeder is installed correctly you can do a "broken union" test to isolate the feeder and see if it's leaking. You may want to take the wires off the feeder and see if it's still putting water in. It doesn't take much of a leak through at city pressure to flood a boiler.
  • Roger Litman
    Roger Litman Member Posts: 64
    May be a leaking tankless

    Your problem is probably either one of three things, the feeder leaking by, the tankless leaking into the boiler through a pin hole, or clogged very slow returns holding back the condensate while the feeder adds water. Once in a while we find shut off valves in radiators that are causing this problem. Get a good tech to your house.

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