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PSE801 LWCO sometimes not functioning properly?

Have a problem that I can probably fix pretty easily, just looking for a little insight first. This probably happens pretty often, as I notice it a few times a week. Thermostat calls for heat, boiler switches on. A minute or two into firing, the lwco will shut off the boiler for about 30 seconds and blink red. Without any filling, the boiler will kick back on and resume normal operation. The water level is fine, not low.

Does this sound like a probe problem? If so, can the probe be cleaned? Or only replaced? Installer used some type of blue thread seal when installing the probe.

$50 for a probe, $150 for a new 801. Is there a "better" lwco I should be getting?

Thanks for the help.

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 17,152
    Well, the obvious question is... what does the gauge glass read while this is happening? The gauge glass is god -- if it reads that the water level drops when the LWCO trips, the LWCO is just doing what it is supposed to do. You would need to find out why the water level is dropping. However, if the gauge glass is stable, the first thing would be cleaning the probe. Don't throw parts at something until you are sure that the part is the problem...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mookie3333
    mookie3333 Member Posts: 82
    Nothing's doing with the sight glass. The water level doesn't drop. This is why I suspect the probe. What can I use to clean it? Is this info in tloash? I bought a copy months back and "hid"it from my two year old ... Now I can't find it myself :smiley:
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,512
    What LWCO is it? If it the "cycleguard", then unfortunately, it is doing what it was designed to do- shut off the boiler every few minutes, in case there is a water level problem.--NBC
  • mookie3333
    mookie3333 Member Posts: 82
    Hi Nicholas,
    No, is a McDonnell Miller PSE 801-120.
  • BobC
    BobC Member Posts: 5,231
    Does the sight glass show any signs of movement when making steam, does the level drop if you drain water from the boiler? If it doesn't the ports to the sight glass might be gunked up and need cleaning.

    If the sight glass is working then the LWCO probe has to be removed and cleaned.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • vaporvac
    vaporvac Member Posts: 1,520
    Hopefully a pro will chime in, but I seem to remember reading that no tape should be used as it can interfere with readings. Anyone?
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • BobC
    BobC Member Posts: 5,231
    edited April 2016
    You do have to make sure the probe grounds out to the boiler block, that cam be confirmed with an ohmmeter. If it's tightened down properly it's hard to believe the threads won't bite through the tape.

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