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Testing a back-up LWCO

Now that my hammering problems are under control I'd like to test the main and back-up LWCO devices.

The primary is a mechanical (float) MM type and testing is straight forward enough -- open a drain while the boiler is running and wait for the cut-off to happen. The back-up is a electronic (probe) type and I believe it is at a lower water level than the mechanical. To test it I think I would have to disable the primary unit from working and let the boiler drain down ever further. Would you experts just disconnect an appropriate wire from the mechanical unit to do this?

Either way, I will test the mechanical now and test the other at the end of the season. I don't want my wire-lifting or running the boiler too low to cause the very problem I am trying to avoid.


  • Fred
    Fred Member Posts: 8,542
    edited December 2017
    Those devices are wired in series so removing one wire will disable all of the safeties, Pressuretrol, both LWCo's etc. To by pass the MM, take both wires off (the ones that complete the safety circuit, not the ones to any auto water feeder) and wire them together, temporarily. That will complete the circuit with only the probe LWCO in the loop.
  • arbalest
    arbalest Member Posts: 80
    Thanks @Fred.
    EBEBRATT-Ed Member Posts: 15,344
    you can also buy a probe type cutoff with a test button in the future.......next time.
  • BobC
    BobC Member Posts: 5,473
    Am I right about that test button just checking the electronics and not testing the probe itself?

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge