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Low Water Cutoff Question

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wildrage
wildrage Member Posts: 187
So I’m downstairs tonight installing my new Vaporstat and 5 psi gauge, waiting and watching for water to boil and I notice the level is a little low.  I watch it drop down just to the bottom of the glass but not far below.  I think I remember the low water cutoff feeder kicking in at around this time. 

So I figure okay.  Let me test the low water cutoff.  So I pull the drain valve with the furnace on, and nothing happens.  I keep it open.  The water level bounces up and down in the glass but doesn’t go straight down. 

I try this many times.  I notice a “click” after I close the valve, but at no time does the boiler turn off. 

I sort of wanted to try out, when I had more time, taking turns level down to a level that obviously was too low and see if the boiler would kick on just to be sure the switch was bad. 

Do I need a new low water cutoff? 
Is it odd that the feed wasn’t tripping either?  

It’s a McDonnell #67 and over 300 bucks, so I just wanted to check here first before I got out and buy one to install tomorrow.  

Comments

  • jhewings
    jhewings Member Posts: 139
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    I would confirm it is wired correctly by checking the manual. If wired correctly then test the switch with a continuity meter with the wires removed. If the blow down valve is closed and the water level is adequate, you should have continuity between the appropriate contacts. When you open the blow down valve you should not have continuity. BTW the boiler should not be able to run if the wires are removed. If the switch tests ok, there is likely a wiring error somewhere and buying a new 67 will not help.
    wildrage
  • jhewings
    jhewings Member Posts: 139
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    If you don't have a meter you could also remove the wires from the switch. If the wires are not touching each other, the boiler should not run. If you touch the wires together, the boiler should run.
    wildrage
  • jhewings
    jhewings Member Posts: 139
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    Turn the power off first before removing wires
    wildrage
  • Jamie Hall
    Jamie Hall Member Posts: 23,313
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    The click was, most likely, the switch in the LWCO opening or closing. Useful noise. A couple of thoughts, though. First, the LWCO level of a 67 is below the automatic feeder level. Second, many automatic feeders have a time delay on feeding, which may be why it didn't feed.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    wildrage
  • wildrage
    wildrage Member Posts: 187
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    Thanks guys. Went to local shop today and they don’t have any LWCO switches in.  Got on from supply house that will be here on Monday.  

    In mean time I decided to try and clean it.  Drained water down.  Got some delicate brushes from harbor freight, and felt around.  I made contact with the float, which was clicking into the 2 positions and moving freely.

    Then I felt something else.  Please tell me this isn’t a piece of my boiler.  I don’t know how it could be, since the pipes leading to the lwco would just barely be able to pass it.  It is magnetic, but crumbled a bit in my had while i was testing it.

    When I pulled this piece out, the lwco works as it should. 

    Picture below. 


  • wildrage
    wildrage Member Posts: 187
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    Ran the first cycle. Now when I open the blowoff, I hear 2 clicks when closing it. 1 for the feed, the other for the kill. Still very curious to what that piece that was blocking the float was. Piece of the boiler? A bunch of crud that compressed together then got dislodged? Piece of the LWCO housing? Admittedly, I just started using heat, so its been sitting all summer.
  • neilc
    neilc Member Posts: 2,703
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    ugly things grow in there sometimes,
    Karbunkles,
    and that's why it's important to blow down, and service the float and chamber periodically,
    known to beat dead horses
    wildrage
  • wildrage
    wildrage Member Posts: 187
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    neilc said:
    ugly things grow in there sometimes, Karbunkles, and that's why it's important to blow down, and service the float and chamber periodically,
    I'm a compulsive blower downer.  Probably 2-3 times a week...too much. But taking it apart and cleaning it is new to me.  I usually just cleaned out the pig tails. Learn something new every day!
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,533
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    I was going to say maybe it wasn't draining fast enough.

    As far as the switch goes the top two terminals are the lo wate the bottom two are the feeder.

    Sometimes the wire these as a 3 wire (the incoming hot wire feeds 1 of the burner contacts and jumps over and feeds 1 feeder contact
    wildrage