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Water dropping out of sight glass but lwco doesn’t kick in

NYCDave
NYCDave Member Posts: 78
Our boiler water (burnham IN8 steam, one pipe system) drops to the bottom of the sight glass after it runs for a few minutes, but the lwco (safeguard probe style) does not kick in... when boiler is not running, water level is a little above where the probe inserts into the boiler housing. Does that mean the lwco is bad, or just that the sight glass doesn’t reflect the true water level when the boiler is running?

The bottom of the glass is marked as lowest permissible water level... is it a concern if water appears to drop below this while boiler is running even though it returns to middle of glass after boiler shuts off?

Thanks!!!

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,275
    Doesn't matter which it is -- that's a situation you want to get fixed as soon as possible.

    It's rare for a sight glass which responds at all to misbehave. That's why they're there. My bet would be on the LWCO being dirty or faulty. Probe type? Try removing the probe and cleaning it thoroughly then reinstalling. Don't use tape! It has to have a good metal to metal contact with the boiler to work at all.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Fred
    Fred Member Posts: 8,542
    Additionally, Skim the boiler! The water level should not drop like that and more often than not, it does so because there is a layer of oil sitting on top of the water that the steam bubbles have a hard time breaking through. When that happens, it can push the water out into the wet returns. Has this boiler ever been skimmed? If so, has any new piping work been done since it was last skimmed?
  • NYCDave
    NYCDave Member Posts: 78
    Thanks @Fred and @Jamie Hall, you guys always give great advice! I will definitely try to skim again. System has been skimmed, but maybe not well enough. I will clean the probe.. if I don't use tape, do I use dope, or just screw it back in?

    I will also thinking I can just turn the thermostat down and then drain the boiler water below the probe level and see if the LWCO light comes on? Would that be a good test?
  • Jamie Hall
    Jamie Hall Member Posts: 23,275
    NYCDave said:

    Thanks @Fred and @Jamie Hall, you guys always give great advice! I will definitely try to skim again. System has been skimmed, but maybe not well enough. I will clean the probe.. if I don't use tape, do I use dope, or just screw it back in?

    I will also thinking I can just turn the thermostat down and then drain the boiler water below the probe level and see if the LWCO light comes on? Would that be a good test?

    I'd just screw it back in -- doesn't take much torque.

    A better test is to get the boiler running happily and then drain it down to the bottom of the sight glass. The LWCO should turn it off. Then, if the LWCO is an automatic (which most of them are) wait a bit for any condensate to return and refill as necessary to bring the water level up to say a quarter glass and pause -- after no more than a minute the burner should kick back on (make sure the thermostat is still calling!)
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • NYCDave
    NYCDave Member Posts: 78
    Good news... boiler water has been slowly dropping over last two weeks (need to replace some vents I think... maybe some valves as well), so last night it was only a bit above the LWCO probe, so I just decided to drain some water and see what happens... I had the thermostat down, so boiler was off, because when it's on the surge is so bad I can't tell where the water line is... as soon as the water dropped below the probe, the little orange light on the Safeguard lit up... I turned the thermostat back up, boiler did *not* come on! I slowly added water, and as soon as the level cleared the probe, the boiler came on. So it seems the LWCO is fine, and despite the water surging way down in the sight glass, there is still water in the boiler. So the next step is to skim... I've never done it myself. I assume there must be lots of info on here as to how to do it... can anyone provide a link perhaps?

    Thanks!!