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Low Water Cut Off - red light on - boiler has water

Jshine Member Posts: 19
My LWCO is indicating low water when I have plenty of water.  I even removed some water and re-filled - it stays on.  I shut the power off - light goes out - turn it back on - the red light stays off for a few seconds and then comes on.

I have McDonnell Miller probe type - PS-802.  The boiler was installed about 15 years ago and I was finally scheduling a maintenance after reading this forum.  I have a call in to my local plumber - but of course it's Easter weekend.

Is there any way to temporarily by-pass the LWCO to allow the boiler to fire up?



    RDSTEAM Member Posts: 134

    do NOT bypass that safety. remove the LWCO and make sure the probe is clean. could be something as simple as that. there should also be a wire going from the probe to the board. make sure that is plugged in and in good shape. when you drain the boiler does the water in the sight glass dropping down? make sure you can actually see the water line.
  • Jshine
    Jshine Member Posts: 19

    Yes - when I drain water I see the water level in the glass move down.

    also - when I depress the "test" button I see an amber light (kind of faint)

    Should I wait for the plumber to remove/clean the probe - or is that something a homeowner can tackle?
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,322
    If you are not quite handy

    I would leave it to a pro to remove and clean the probe. It may be beyond needing cleaned. The Probe may be corroded. Is there a reset on the LWCO? Some are manual reset models.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • ed wallace
    ed wallace Member Posts: 1,613
    lwco red light on

    where are you located maybe someone on this forum is near you
  • Jshine
    Jshine Member Posts: 19

    hello all -

    Local plumber responded and stopped by - Smithco - Tom Smith - Morristown NJ - turns out the actual 'element" on the probe was broken in 2 - it would randomly make/release contact.  This was diagnosed after removing - cleaning the probe and re-starting the boiler (red light came back on after a few minutes).  He did not have a 1/2" probe replacement - so since the broken element would work if held in place with some tension - he managed to temporarily make it work - he was determined to get this to work (even on Easter weekend) and he did.  He will order a replacement probe on Monday - thanks to all and to Tom Smith.

This discussion has been closed.