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Can someone identify this mechanical LWCO?

nybigapple Member Posts: 59
edited February 2019 in Strictly Steam
My LWCO had been giving me problems where it got stuck and doesn't call for water. Banging on it triggers the auto adder so I know it's a dirt problem. I do purge the boiler every week but it's not enough.

A plumber in passing told me if I can get the appropriate gasket it's easy enough to clean out. If I can't find the gasket, leave the LWCO sealed, and clean it from the top nut. I opened from the top and of course, found sludge. I removed as best I could, so now it doesn't get stuck, but the float is apparently off. It calls for water till about 2 inches over the appropriate LWCO level. Leads to way too much water, and wet steam.

I'd like to order whatever I need to clean this properly, but I don't see any model name or sticker on it. Is it just one gasket? I remove the bolts, and spray/scrape out any sludge right? Anything tricky I need to know about?


  • Fred
    Fred Member Posts: 8,542
    It looks like a McDonnell Miller LWCO. You might check their website for a model #. I see a number stamped on the side of your first picture. That's an old unit and McDonnel typically recommends their mechanical LWCO's be replaced every 10 years. I'm guessing that, if you cleaned it from the top, you either poked a hole in the float or bent/broke the arm that the float swings on.
  • nybigapple
    nybigapple Member Posts: 59
    Ah! Thanks Fred. Think you are right and it's a McDonnell Miller 61. Hopefully the arm is just bent.
    EBEBRATT-Ed Member Posts: 15,614
    Yup MM #61. If you go to the right supply house you can buy just the "head" assembly complete with switch & float and pull the 4 bolts out and replace the head clean out the casting and piping on the boiler. They are $$ The head assembly is just as many $$ as a complete new control.

    Any supplier that sells mm can get you a #61 body gasket.

    If your up for a lot of scraping and cleaning you might be able to save the old one but its a safety control and is probably at it's useful life.

    or take the unions apart and replace the entire control

    Use never seize on gaskets, bolts and unions and it will come apart easy next time