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#67 LWCO

ChrisJ Member Posts: 15,457
OK I have a kinda lame question but I have to ask. On my previous boiler (Burnham V83) if I dumped the LWCO it would shut the burner off long before the boilers water level actually dropped that far. It basically went with the sight glass and then I'd shut the valve and the level would return and shed fire back up.

Tonight I tried doing this trick with my neighbors boiler and.......... it wouldn't shut off.

Is this because the boiler has far more water than mine? its around 60 years old though the MM 67 is fairly new and seems clean. He does his weekly blow downs, always has but never actually knew to test the thing.

I'm just a little cautious of dumping 5-6+ gallons of water out of the thing to trigger it if its unnecessarily. I dumped 3 gallons out and the sight glass only dropped an inch.
Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment


  • gerry gill
    gerry gill Member Posts: 3,078
    nope, it should have

    shut off the fire..there is some kind of issue.
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,849
    That's a bad LWCO

    This is why we test them regularly.The reason it switches off the burners when you open the valve is that the water runs out the blow-down valve faster than it can flow from the boiler to the LWCO, and there isn't enough water left in the LWCO to keep the float afloat. An accumulation of gunk inside the LWCO can either prevent the float from falling when you open the valve or obstruct the water from running out fast enough. Either way, it's failing the test and has to be fixed or replaced.

    I actually have a 67 I just replaced with a probe-type LWCO. I was thinking of selling it, but I got a close look at it over the weekend and and it doesn't look so hot. If you want it it's yours for the shipping. It's 24 volt, has four seasons on it, the valve works and the float is free. No warranty. :)
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
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