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Thread: Boiler: Valve to Automaticly Add Water

  1. #1

    Default Boiler: Valve to Automaticly Add Water

    My mother's steam heat boiler have a low water warning light. When it is on, the boiler will not turn on until the water supply valve is opened to add sufficient water into the boiler. This was OK when I lived there or when my father was younger. Now both of them are OLD and I live far away.

    Are there any automatic water valve to fill the proper amount of water. It cannot imagine that it is that complicated. Use the signal from the warning light to trigger an electrically activated valve. When the water level is back to normal, light goes out, signal gone, and valve shuts off. I can do the installation. I just don't know where to find such a device.

    Are there a commonly used kit available?
    Is it mechanical or electrical?
    How reliable?

    I can see a scenario where the water level float switch get stuck and the warning light do not turn off and the valve stays open. Not good when it is automatic and people may not notice until lots of damage are done.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    I know there are valves that will fill hot water boilers, but haven't needed or looked for one for a steam setup. A hot water system doesn't use a level sensor, it relies on pressure, and maintains that minimum pressure by adding some if it drops.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member edlentz's Avatar
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    Find a Boiler installer / service company where they live. You can go to a site I lurk around alot. Heatinghelp.com They are all (most all) boiler mechanics. There is a place to find a repairman. This is NOT a DIY thing. Steam or hot water heat should be used alot more now more than ever. IMHO.

  4. #4

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    http://www.inspect-ny.com/heat/Steam...er_Feeders.htm

    Found the above web site. Installation seems straight forward and within my ability. I just have to find out who/where they sell it.

    Basicaly, the pump is placed in parallel to the existing manual fill valve. When the water is low, as detected by the float switch level detector, it triggers the auto fill valve to open until the float switch is turned off.

    My biggest concern is the reliability, not of the valve but how it impacts the the system's reliability. I am concern that if the float switch water level sensor/cut-off, which is part of the boiler, if stuck, can allow the auto feed valve to remain open and over fill the boiler. The unit described in the above web site does not seem to have a safety for the event of an over fill.
    Last edited by xroad; 03-29-2009 at 08:38 PM.

  5. #5
    Master Plumber nhmaster's Avatar
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    McDonald Miller 101 automatic feed valve. Installes on the water inlet. Solenoid valve, opens when the low water cutoff drops. Very common on steam boilers. You can get one at any plumbing supply or even special order it at H.D. or Lowes. Be sure to pipe a bypass around it in case it fails in the middle of the night.

  6. #6

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    Quote Originally Posted by nhmaster View Post
    McDonald Miller 101 automatic feed valve. Installes on the water inlet. Solenoid valve, opens when the low water cutoff drops. Very common on steam boilers. You can get one at any plumbing supply or even special order it at H.D. or Lowes. Be sure to pipe a bypass around it in case it fails in the middle of the night.
    Thanks. I'll be installing it in parallel to the existing manual fill valve. So, even when I loose electrical power, or a failure of the solinoid valve, I can still manually add water.

    There are two possible failure mode. Fail to open, and fail to close. Fail to close is the one I feared. The control to the solinoid valve is from the water level switch. If that is stuck, it will never send a signal to close the solinoid valve.

    Am I being paranoid? Do these solinoid valve have a safety built in for such scenario?

  7. #7
    Illinois Licensed Plumber SewerRatz's Avatar
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    In this case when there is no power to the solenoid it will be normally closed. If I recall when they do fail they fail in the closed position from the lack of having to open. It has been forever since I had to work on a boiler, I pass them off to my old plumbing instructor. He has a garage full of parts and the time to mess with these things.

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    Master Plumber nhmaster's Avatar
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    Not only do they fail (usually) in the closed position but they also have a red by-pass button them that usually works. Be sure and put a union on the downstream side so you can do a broken union, leak by test if you need to. Piping directions are in the box.

  9. #9

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    The auto valve, I am sure is very reliable, that is not the problem. If the valve DID NOT FAIL to open or to close.
    If the WATER LEVEL SWITCH on the boiler failed.

    Then the valve will not get the signal to close when the water level is sufficiently high. Water will continue to fill, non stop.

    I have had my boiler's water level switch stuck years ago, when I first bought my house. I was manually filling the boiler so I just shut the valve, with my hand. The stuck water level switch is the result of sludge in the boiler. So, diligent flushing of the boiler is required. That is what I mean when I said the auto valve may just move the problem from one spot to another.

  10. #10
    Master Plumber nhmaster's Avatar
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    Quote Originally Posted by xroad View Post
    The auto valve, I am sure is very reliable, that is not the problem. If the valve DID NOT FAIL to open or to close.
    If the WATER LEVEL SWITCH on the boiler failed.

    Then the valve will not get the signal to close when the water level is sufficiently high. Water will continue to fill, non stop.

    I have had my boiler's water level switch stuck years ago, when I first bought my house. I was manually filling the boiler so I just shut the valve, with my hand. The stuck water level switch is the result of sludge in the boiler. So, diligent flushing of the boiler is required. That is what I mean when I said the auto valve may just move the problem from one spot to another.
    Low water cutoffs should be flushed weekly during the heating season.

  11. #11
    Moderator & Master Plumber hj's Avatar
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    Default Lwc

    Depending on the low water cutoff, there are probably terminals inside the electrical box, probably the same ones operating the light, to activate a feed valve. The voltage to the light may not be the same as that to the feeder so you may have to forego the light, which will no longer be needed anyway, to wire the feeder.

  12. #12

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    As for electrical interface, I am OK with it. I am a military electronics hardware designer. I spend my career thinking in terms of multiple redundancies, fail safe modes, and ultimate reliability. So that is where my paranoia comes from.

    Without the auto feeder, worst case is low water and the boiler will not fire due to the low water cutoff switch.

    With the feeder, worst case is water won't shut off and over fills the system, flood basement, and water coming out of the radiator vents, only to be discover hours later.

    Looks like by adding the auto feed valve, the system maintainance requirement increased.

  13. #13
    Master Plumber nhmaster's Avatar
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    Because the low water cutoff is float operated the worse case senario is that the float fails to drop when the water level drops and the boiler runs out of water and cracks or worse, burns the house down. The feeder is wired to the # 4 terminal of Mcdonald Miller 67-2 and the older 47 series also. The warning light or alarm can also be wired off the # 4 terminal. Commercial applications install a secondary low water cutoff in series with the main operatin cutoff and at a slightly lower level. We usually use an electronic unit for that like a Hydro-Level or even McDonal Miller makes one.

  14. #14

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    Ha! Of course. Dry boiler and the flame kicks on ... yes, THAT is the worst case scenario.

    A second cutoff float switch, where is that mounted? On my boiler, there is a metal "thing" where the pressure cutoff, water level cutoff, and the flush valve are attached. This "thing" is piped to the top and ottom of the sight glass.

    By the way, what ball park price are these auto feed valves?

  15. #15
    Moderator & Master Plumber hj's Avatar
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    Default fill valve

    How much do you want to spend? You can buy a simple solenoid water valve for a few dollars or a McDonnell Miller one for a few hundred.

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