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Is it Low Water Cutoff or is it Pressuretrol

John_23 Member Posts: 2
I was on a no heat call with a Low pressure steam boiler job today. Folks moved into the house 2 years ago and haven't had the boiler serviced or ever blown down the McDonald Miller #67 LWC.

It was off on low water or so I think. I cleaned out the # 67 and she worked but everytime I put the pigtail on with the pressuretrol on top of it it ceased to function properly

Is it the lwc or the pressuretrol? The pigtail was also dirty but I cleaned it out.

Thanks in advance for the replies


  • Clean the little

    opening into the pressuretrol and blow it out. Take the pigtail and get it cherry red from holding it in a flame. Then drop it in a bucket of water to blast it clean. Blow it out and reinstall. If that does not work on the pressure trol replace it. As for the low water cut off take it all apart and clean it out, replace the blow down valve with a new McDonnel 67G blow off valve. Make sure the sylphon base (float) does not have a hole in it. Bring the boiler on and blow down the blow off to make sure it shuts off.

    Make sure to instruct the customer on how to maintain thier boiler.
  • Bill NTSG
    Bill NTSG Member Posts: 321
    Iron F.

    The pressuretrol screwed into the tapping on top of the M/M 67? Was it a brass pigtail ? Maybe it threaded in so far that the pigtail nipple came into contact with the float? Just a guess...
  • John@Reliable
    John@Reliable Member Posts: 379
    LWCO or Pressuretrol

    Which pressuretrol are you using and what is it set at ? Sounds like it may be the problem. As for the pigtail replacement is quicker than cleaning. I find that the 404 which is set low will over time need to be adjusted higher to work right,go to allot of no heats like this,one way to know for sure is to test for power @ both or jump pressuretrol while there and see what happens.
  • Also check

    to see that the upper nipple for the gauge glass is not plugged as well. Usually this can be cleaned by taking off the upper valve stem and bonnet assembly. Hope this helps.

    Glenn Stanton

    Burnham Corp.
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