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Water Feeder Overfilling and Shut Down

JohnCTJohnCT Posts: 28Member
I have an oil fired boiler for hot water and steam heat. The auto filler frequently overfills the boiler causing it to shut down. It calls for water even when the water is almost to the top of the sight glass. It does this both during the heating and non-heating season, so doesn't appear to be from water returning slowly. I'm pretty good at draining the sediment on a regular basis trying to keep what I assume is a float valve unobstructed. I've had my oil company service people look at it several times (I think Dan would refer to these people as knuckleheads). They messed with settings on the filler, but nothing changed. Is there any harm in simply shutting off the water supply valve to the auto feeder and monitoring and manually filling as needed? Or should I find someone who knows what they're doing and get the feeder fixed or replaced?


  • Jamie HallJamie Hall Posts: 10,293Member
    JohnCT said:

    ... . Is there any harm in simply shutting off the water supply valve to the auto feeder and monitoring and manually filling as needed? Or should I find someone who knows what they're doing and get the feeder fixed or replaced?

    No and probably wouldn't be a bad idea to really find out what the problem is...


    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • FredFred Posts: 7,815Member
    You mention that this boiler provides steam and hot water. I assume you mean potable hot water through a tankless coil, in the boiler. If shutting the water to the auto fill doesn't resolve the problem, the tankless coil is probably the problem. It may have a pinhole in it that leaks into the boiler cavity, overfilling the boiler.
  • JohnCTJohnCT Posts: 28Member
    Thanks, Jamie!

    Fred: So far, it only seems to overfill when the feeder supply is open, but I'll definitely watch that. Thanks!

  • The low water cut-off probe should be pulled, checked, and cleaned if necessary.

    New England SteamWorks
    Service, Installation, & Restoration of Steam Heating Systems
  • BobCBobC Posts: 4,947Member
    Take a picture of that LWCO and include enough of the boiler so we can make sure it's mounted in the right place.

    I have lived with steam heat for over 70 years and never had a boiler with auto fill, I think they cause to many problems. Just be sure you inspect the boiler a few times a week to be sure the water level is ok. Check that the boiler does shut down if the water gets too low a couple of times a year.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • GBartGBart Posts: 753Member
    Is it a LWCO / feeder combo with mechanical linkage? Probably over ten years old, probably shot. Take a good screwdriver and put it to the pipe at the feeder with everything off but the valve to that open, put your ear to the screwdriver handle (poor mans stethoscope) and listen for seeping.

    Most LWCO's are listed for mandatory replacement at 10 years for safety.
  • GBartGBart Posts: 753Member
    auto feed look like this?

    the seats are known for not sealing after many years or as stated your hot water coil may be leaking internally

    shutting off one then the other for a day each would prove who the guilty party is
  • If the feeder was installed properly, there would be a union downstream, which can be opened to verify flow or no flow.
    Does the LWCO shut off the boiler when you flush it?
    Another possibility could be high pressure, during steaming, causing enough water to rise up in the returns to simulate a low water condition in the boiler.--NBC
  • GBartGBart Posts: 753Member
    311 gallons??? holy crow, you're going to lose the boiler

    you may have slow returns so the lwco thinks it's low and auto feed kicks in, you have a great auto feed that has options which can solve this problem, you want to set the feed delay and the feed amount options, this may take some experimentation but generally the feed amount should be set to LWCO to prevent over filling, the feed delay option is supposed to come from the factory set to 2minutes, if it is increase it, as you make steam if your system is slow to return the condensate the lwco will signal for water as this happens you are adding water you don't need so eventually the unit overfills, we used to add delay on make timers to them but this solves you also need to try to address why you're returns are slow, like are they 100 years old in the floor or are the returns full of muck?

    manual for VXT states: The feed delay feature is designed to prevent boiler flooding by allowing time for condensate to return to the boiler prior to feeding. If the returns and vents are in good condition, the 2-minute factory setting is usually sufficient. If for any reason condensate takes longer to return to the boiler (such as old return lines or long horizontal runs), a longer delay setting should be selected.

    see the manual--
  • JohnCTJohnCT Posts: 28Member
    GBart: The delay was one of the things my oil company service tech tried. I think it's on 4 minute delay now. This is happening during warm weather when the heat hasn't been on for months, so I'm assuming it's not a slow return issue. Also, I've watched it, and the feeder is calling for water when water is 3/4 of the way up the sight glass. Let me know if that logic is faulty. I do use the boiler for hot water, but hard to imagine that's creating a lot of steam in the system.
  • GBartGBart Posts: 753Member
    Wondering if it's wired correctly then, based on your LWCO center line and the height of your water there is no way it should call for water, although I've seen glass gauges that had blockage and weren't indicating the actual water level. The wiring should be according to the float diagram in the manual, a boiler your size would be limited to 6-8 gals a month so 311 gallons would be accurate at 4-5 years of service.
  • JohnCTJohnCT Posts: 28Member
    Thanks again, GBart. I'm going to try again with the oil company tech and try to get him off the filler and focused on the LWCO. I think the guys they're sending out just aren't that experienced. But I do have a service contract with them that covers auto filler and LWCO, so I'd like to see them resolve it rather that trying to find someone else. Thanks for your great input. What are your thoughts on Utica boilers? Any experience with them? Anything else to be concerned about?
  • FredFred Posts: 7,815Member
    I'm thinking the auto water feeder is not wired correctly. The VXT is wired differently for the McDonnell Miller #67 LWCO than it is for the probe type LWCO's. Look at you owners manual for the auto water feeder.
  • JohnCTJohnCT Posts: 28Member
    Thanks, Fred. Would you say that if the overfilling is intermittent? It might go a month without doing it, then every day for a week, then suddenly stop, etc.
  • FredFred Posts: 7,815Member
    JohnCT said:

    Thanks, Fred. Would you say that if the overfilling is intermittent? It might go a month without doing it, then every day for a week, then suddenly stop, etc.

    That sounds more like the water valve, inside the auto feeder is not consistently seating or gets some dirt/crud between the valve/solenoid plunger and the valve seat. When it doesn't completely seat, it lets water leak by, when it does close completely, water level stays where it belongs.
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