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Boiler Overfills When Off!

Steamhead--that Sears boiler of mine, the label says made for Sears by Dunkirk Boiler Co, Dunkirk, NY. Input 225,000---Output 180,000, Series PVS225, Model 2299962270
Nothing else on the plate that would help identify this, and the plate cites some standards of 1976.
So what can you tell me about this?


  • My boiler overfills.

    Here is the situation. I have an old system, we moved her in 11/05. On the boiler is the standard MM67 Low water Cut-off, an records on the boiler indicate it was installed in 9/03. There is also an MM Series 101 Feeder, date unknown (but there long enough that when I went to clean it this summer, I found the strainer completely caked and no water passing, and could not remove the cartridge)

    Testing while the boiler is steaming, both seem to be operating properly. When I blow it off, it shuts the boiler, and kicks in the fill, and does not overfill. I have even seen it shut for low water and then fill.

    The problem comes when the water is at a lower level and the boiler is turned off by the thermostat. The feeder kicks in and does not stop. I have to give the cut-off a knock to stop it, and this certainly can’t be good. I heard it through the house this AM and after stopping it I removed over 4 gallons of water to get the level to bounce down into the sight glass.

    My guess is the float in the cut-off needs cleaning. My reason for this is that we had some serious problems after we moved in, the first 30 feet of main pipe rotted and leaked, and we had a knucklehead (warranty work, and I had not yet bought the book!) in who dumped “conditioner” into the system and fouled it up terribly.
    Ultimately I wound up with a new pressuretrol, relief valve, and pressure gauge, someone knowledgeable cleaned the system, and this summer I replaced most of the vents, including the main, and insulated all the exposed pipes in the basement. And the system does run nicely—except for the overfill issue.

    If my diagnosis is correct—will I regret disassembling and cleaning the float and stuff? I have the float mechanism replacement instructions printed out from MM’s site. Is there any replacement part I need?

    Or do you guys think there is a different culprit here?
  • Know thine enemy..

    There's no point in cleaning the LWCO if that's not the problem. The most important thing to do is figure out if the plunger is sticking or the switch. It is possible to replace just the switch and avoid removing the float but you need to know what the problem is.
  • I don't think it is the plunger

    in the feeder because:
    When it is in this stuck mode, I can kill the power to the entire cirtcuit and the plunger immediately pops up and the water flow stops, then put the power back on and the solenoid jumps the plunger back down again.
    So for whatever reason, it appears that when it is in this mode something is preventing the feeder from being told that the water level is good.
    Which is why I think the problem is in the LWCO, which is where this info comes from.
    BTW, there is a clear buzz or hum coming up that I can hear elsewhere in the house while the solenoid has the feeder feeding (along with the click of my water meter), so I am aware of whenever this works properly or sticks.
  • John@Reliable_14
    John@Reliable_14 Member Posts: 171
    Sounds like a bad..................

    switch on the #67. Over the years I've learned to change both the switch and float as one. To many call backs it seems when only the switch is changed. Make sure you blow down the 67 weekly under steam and to check that the LWCO is working by draining the boiler thru a bottom boiler drain, not thru the 67 only. M& M also recommands complete unit replacement every ten years. You could also change over to a probe type LWCO which requires only annual removal for cleaning. No weekly blow down = less raw water = longer boiler life.
  • William Faust
    William Faust Member Posts: 168
    Probe LWCO's

    How much do probe type LWCO units cost anyway?
  • Depends

    on where you get them. They can cost as much as a #67.

    But the real issue is whether the boiler has the proper tappings to install a probe. If not, there's no point in getting one.

    Larry, what make and model of boiler do you have?

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Boilier make

    Steamhead--I have no idea!! The info from the plate is from Sears, and the plate was printed in 1979. I am guessing it went in between 79 and early 80s, the second previous owner of the house was 85003, and said they did not put it in.
    I have tried to get info from Sears and they have been no help whatsoever.
    The most distinguishilg thing is the steam exits sideways, one lead only, from the upper back corner of the right side panel, which is also where the LWCO and the pigtail are mounted. If you think it will help, tell me to copy down any other info from the plate when I get home.
    The bad switch idea sounds plausible--but doesn't the same switch control all the functions inside the LWCO?
This discussion has been closed.