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Low Water Cutoff Light on - Water level at top of gauge

Dathanz Member Posts: 34
edited December 2022 in Strictly Steam
Question for the group.....I'm currently out of town and am trying to diagnose my boiler issue through a friend I have checking on my house.

Temp in the house is 32 degrees so my boiler has stopped running for the past couple days. The LWCO light is on but the sight glass shows water slightly above the high water level line so there is plenty of water in the system. I had him turn the circuit breaker to the boiler off and back on. Now both the LWCO light and the intermittent test light is on, the intermittent test light was not on prior. A good 10 minutes passed and the intermittent test light stayed on, which I believe should have been sufficient time for it to run the initial start up test.

It just seems like the LWCO is shutting the system down even though the gauge shows sufficient water.

Any ideas? Would a clogged pigtail cause an issue with the LWCO sensing the correct water level?

Disclaimer....my friend had added some water to the system while I was away which caused it to read high pressure, thus the system initially shutting down from pressure. Once I had him drain some water out, the pressure dropped back to zero, and the system fired back up. This was about a week ago and today is the first day he went back to check on it.

I'm 6hrs from home and if I can't diagnose remotely I'll be heading home this afternoon to try and figure it out myself. Thought I'd see if anyone has any ideas so I don't have to cut my holiday trip short.

1 Pipe Steam System | Upstate NY


  • Jamie Hall
    Jamie Hall Member Posts: 22,947
    Presumably this is steam? Since you seem to have a sight gauge? Your friend adding water enough to shut down on pressure did you no favours, and there may be problems resulting from that -- but we'll cross that bridge later.

    First, a steam system without a functioning low water cutoff is not safe to operate. Period. Your low water cutoff is not functioning. Therefore... Unless you can have a reliable and knowledgeable person there to monitor the water level in the sight glass while the boiler is running -- and doing absolutely nothing else -- pull the emergency switch to off, drain the house, and wait until you can get someone in there to find out what's wrong.


    Now on what's wrong. The likelihood is that the low water cutoff is not correctly sensing the water level. This isn't a pigtail problem. If it's a float type, the odds are that the float is stuck down (those things need to be blown down from time to time to ensure that that doesn't happen). That's a simple enough repair, but the system can't be run until it's done. If it's a probe type, there are several problems which might be present -- it may just need to be cleaned, but the electronics may have failed. Again, not that difficult a problem to fix.

    But I will repeat. The boiler can't be run until you have a functioning low water cutoff.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Long Beach Ed
    Long Beach Ed Member Posts: 1,188
    edited December 2022
    Some low water cutoffs will lock out after several unsuccessful attempts to correct the low water condition. Cycling the power should have reset that.

    You did say you reset the circuit breaker. I would cycle the main service switch, check that the water level in the sight glass is proper and see if that corrects the problem. If not, the low water sensor needs attention.

    You may also review the installation instructions (usually online) for your particular low water cut-off and make sure there an no fault codes that you overlooked or reset procedure that is particular to your device.
  • Dathanz
    Dathanz Member Posts: 34
    edited January 2023
    Just following up on this for the good of the board.

    I did end up going home to assess the issue. What I found was regardless of adding or draining water the water level in the sight glass was not moving.

    I removed the sight glass and found it was clogged at the top. Once I removed and cleaned that out it started to register the correct water line.

    Simple fix!
    1 Pipe Steam System | Upstate NY
    Long Beach Ed