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The lwco is overflowing the gas fired boiler (steam heat)

bob2013 Member Posts: 1
I have a relatively new boiler ( 2 years), with a low water cut off system , Mcdonnell PS802-24. The thing is working fine when the water is low, feel up half of that water line, stops, then feed water again, then stops then goes on again, ending up over-feeding the boiler that shuts of. I disconnected  the water feeder, so now when the water is low, the LWCO tries to add water but will not be able. So add water, reset the LWCO, then the boiler  works fine again. I would appreciate any help.

Maybe relevant, I found the voltage transformer ( 120 to 24vac) warmer than what it should be.




  • Steamhead
    Steamhead Member Posts: 15,886
    I'd first check the probe on the PS-802

    if it's dirty it won't detect water like it should. But if there's that much dirt in the boiler, it will need to be flushed as well.

    Where are you located? There's likely a good Steam Man near you. Try the Find a Contractor page of this site.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
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