The Wall
Forum / THE MAIN WALL / clogged low water cutoff valve
  • Post a Reply to this Thread

    clogged low water cutoff valve (11 Posts)

  • Brian O'Hagan Brian O'Hagan @ 9:14 PM
    Contact this user

    clogged low water cutoff valve

    All winter I have been using the low water cutoff valve to "change the water" in my system (steam single pipe) and get rid of the built up sediment. I've been doing this every 2-4 weeks until lately i slipped to ~ 6weeks. When i went to let the wwater out last night only a few drops came out. I think my system still has water as indigated by the vertical glass water gauge. The gauge is 3/4 full and when i add more to the water system the water level in the gauge goes up. it seems to me that the cutoff valve is glogged. Any ideas how to confirm this and to clear it up? thanks brian
  • Steamhead Steamhead @ 10:38 PM
    Contact this user

    If it's a McDonnell & Miller LWCO

    and the blow-down valve has a knob, have it replaced with a ball-type valve (part #14B) which is operated by a yellow lever about 5-inches long. If you already have a 14B blow-down, it can be cleared by sticking a screw driver up thru the outlet. This should also be done by a pro to avoid damaging the internal float. It sounds to me like there's a lot of dirt in that LWCO. Once the problem is fixed, blow it down every day for at least a month. Do this while the burner is running. If the burner does not stop when the open blow-down drains the float chamber, HAVE IT FIXED RIGHT AWAY! If the LWCO does not stop the burner when the water level drops, the boiler will crack. To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"
    Steam and Vapor heating- the BEST!

    Baltimore, MD (USA) and consulting anywhere.

    We're reducing our country's energy usage, one system at a time.
  • Noel Noel @ 5:59 AM
    Contact this user

    Plugged LWCO

    > and the blow-down valve has a knob, have it
    > replaced with a ball-type valve (part #14B) which
    > is operated by a yellow lever about 5-inches
    > long.
    >
    > If you already have a 14B blow-down, it
    > can be cleared by sticking a screw driver up thru
    > the outlet. This should also be done by a pro to
    > avoid damaging the internal float.
    >
    > It sounds
    > to me like there's a lot of dirt in that LWCO.
    > Once the problem is fixed, blow it down every day
    > for at least a month. Do this while the burner is
    > running. If the burner does not stop when the
    > open blow-down drains the float chamber, HAVE IT
    > FIXED RIGHT AWAY! If the LWCO does not stop the
    > burner when the water level drops, the boiler
    > will crack.
    >
    > _A
    > HREF="http://www.heatinghelp.com/getListed.cfm?id=
    > 157&Step=30"_To Learn More About This Contractor,
    > Click Here to Visit Their Ad in "Find A
    > Contractor"_/A_

  • Noel Noel @ 6:07 AM
    Contact this user

    Plugged LWCO

    With that much sedement in there, the float has sedement on both sides of it, too. when the water drops, the float will stay glued to the walls. Go ahead, try it.... Flush the control with the burner running (as per your instruction sheet)until the burner shuts off. If it doesn't shut off, the float is stuck. Don't drain below the glass, if it stays running. Shut it off, and have the control taken apart and scraped clean. This should be done yearly, without fail. M. M. controls are to be replaced after ten years, per their instructions. The responsability of an old LWCO is entirely the operator's. A neglected LWCO that causes a dry fire condition voids the boiler warranty. Noel
  • Brian O'Hagan Brian O'Hagan @ 9:42 PM
    Contact this user

    now i'm a bit confused

    I went downstairs with a screwdriver to try and unclog the valve and didn't need to. When I tried draining the water again (before I did anything), it worked just fine. I drained all the water out of the system/boiler and filled it back up. The water that came out was pretty murky (well brown actually) - towards the end it got a little clearer but not crystal clear. any thoughts as to why it would just start working? b
  • Noel Noel @ 11:08 AM
    Contact this user

    Did it stop the burner when you opened it?

    If it hasn't been cleaned in a year, I'd call for service on it. Noel
  • Brian O'Hagan Brian O'Hagan @ 2:33 PM
    Contact this user

    The bunner was not on. That is, the system was switched on but the thermostat didn't have the boiler being heated. So the system didn't turn off b/c it was not on. I have tested this in the past (when the burner was on) and it did shut off like it's supposed to. I'm planning on getting the unit serviced but i was going to do it in the fall. Actually, I was planning on a few things: 1) getting the furnace/boiler serviced; 2) having a main vent installed since i don't have one (recently found that out); 3) having the rads cleaned (internally). Should I be waiting for the fall or is this best done now? thanks brian
  • Noel Noel @ 2:39 PM
    Contact this user

    check your procedure out

    If the burner isn't running, you cannot flush until the burner stops, which is what this test is for. You flush and test weekly so that you can tell when the float is stuck. If it isn't running, you can't tell. Check your instruction sheet again. It shows how to flush and test. I wouldn't wait till fall, unless you shut it off in the mean time. Noel
  • George George @ 2:42 PM
    Contact this user

    LWCO

    Immediately get that situation fixed!!! The LWCO is the last link in the chain to prevent a bomb from exploding (your boiler)! As far as cleaning it out, after you get the LWCO fixed, I would speak to some reputable water treatment professionals to test the "sludge" and give you some suggestions on the proper chemistry to remove and clean the boiler. Scott
  • hot rod hot rod @ 10:38 AM
    Contact this user

    Stop the presses!

    Sounds like your boiler was in a partial vacuum. If you were attempting to blow down the LWC after the burner shut off, you can end up having a vacuum within the system. First time that happened to me, I disassembled the LWC - only to find it clean as a whistle! Upon reassembly, it worked like a champ. Scratching my head, I ran the system & tested the cut out function to ensure burner shut down. Following the cycle, I once again hit the drain valve & it happened again - no water. In fact, it sucked in air! This time, I glanced at the pressure/vacuum gauge & sure enough - she was in the negative. Thanks to Mr's Warren & Webster, the air I had inadvertantly injected was rejected from the system. I've seen this phenom many times since then. To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"
  • Edward A. Carey Edward A. Carey @ 11:01 PM
    Contact this user

    LWCO

    Brian, One very important thing to remember when flushing a LWCO is that the boiler must have steam pressure on it, or the water will flow out the blow down valve, but will not circulate up into the float chamber. Normally I recomend that some one turn their thermostat up HIGH and let the radiators all get hot. Then you can be sure that you have pressure on the system. Blow down the LWCO at once per week, with the boiler under pressure, and the burner on. Verify that the burner shuts off when you flush the control. You must still have the control disassembled and COMPLETELY cleaned internally, once each year. Also, DON'T use a plastic bucket. The water is not just hot, it is "boiling". I spent some time talking to some very nice nurses in a burn center in 1972, when I learned that little tid bit about flushing a LWCO. Good Luck, Ed Carey
  •  
Post a Reply to this Thread