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Low Water Cut-off Installed Too High? Comments Appreciated

cubicacres Member Posts: 358
edited November 2021 in Strictly Steam
Over the years we've wondered what causes our WMC EG-75 single-pipe steam boiler to shut off (apparent short-cycle?) as we watch it. Often the water feeder light blinks (8 min delay to use condensate water return we timed at around 6 minutes & fills back to the LWC level), or the Tekmar device shows the room is warm enough already even as it begins to fire (shows boiler run % at 4% recently, so we think the Tekmar is stopping it sometimes), or we wonder how accurate our pressuretrolls are set with that 0-30 psi range instead of a 0-3 psi vaporstat (we do have a 0-3psi gauge that suggests it's a decently low 0-up to1.8 psi range each time). Low water, adequate room temperature already, pressure, or ? -hard for us to tell what's cutting-out the burners each time as we observe it (or if it's just doing what it should do & stop the heating if not necessary anymore for the moment).

Yesterday, our tenants mentioned it was cold, and the low water cut off was blinking as the boiler stopped running several times (the same colder tenants are on that longest main line so get less minutes of run time each cycle), but we're not losing water per the water meter & the sight glass looks decently full. Today, we thought about the manufacturer's sign on the boiler (see photos) that mentions min. operating water level at 1/4 inch above the sight glass (it never drops to below the sight glass that we've observed per the dangerous absolute min. 1 inch below level mentioned on the sign), but saw the probe tapping might be around 2-3 inches above the bottom of the sight glass per the photos. Does this not give us very adequate water each time & explain some of the frequent blinking episodes we see as it shuts off? We used a knife per the photos since we didn't have a level.

Does this suggest we should put our low-water cut-off probe on another slightly lower tapping to the right in the photos (bring it down 2 inches to be close to that 1/4 inch above bottom of sight glass level), or that the 40% up the sight glass or so black marker mark the installers drew for us is an inch or two too low for our best boiler operation each time?


    EBEBRATT-Ed Member Posts: 15,510
    In my view the job of the LWCO & feeder is to protect the boiler not necessarly maintain the optimum water level which should be 1/2 a glass.

    The feeder is not a substitute to checking the boiler and adding water as needed

    The low water cutoff looks like it's in the correct tapping
  • archibald tuttle
    archibald tuttle Member Posts: 1,085
    @EBEBRATT-Ed agree, and using the same probe for level maintenance and cutout confuses those functions a bit even though quite common. But what is not detailed in the post is: after cycle, left to fully return condensate, what level is then acheived in the tube or even is the boiler filled a bit above the tube. This could be a case that skimming is needed to cut down on quantities of water moving up in the system w the steam.

    No substitute for checking water but depending on the size of the system if it is down every day, you would be well served by figuring out where it is going.
    JUGHNE Member Posts: 11,058
    What type of return piping do you have?
    Wet return at or under the floor or hanging high....with correct slope?
  • NYtimebomb
    NYtimebomb Member Posts: 30
    Your sight glass has some very dirty water. Have you considered cleaning by skim & blow down?
    It's possible your water is surging and getting low enough to trip the LWCO.
    I'd start there.
  • cubicacres
    cubicacres Member Posts: 358
    edited November 2021
    Thanks for the comments. We timed the condensate water return at around 6 minutes, and it fills back up to around where it was before the burners started. On a typical month, we noticed 1-3 gallons of water added per the feeder's meter if we don't notice any obvious leaks, so hopefully this is an ok water use baseline (there may be some leaks we haven't found in tenant's units occasionally since they don't notify us very often other than replacing a failed open spitting air vent on a too hot radiator that never closes :smile: .

    3 branch main lines rise to the the last radiator from the main line on the basement ceiling. Dry returns sloped downhill ok after the last radiator to the boiler, until the condensate lines drop down 2-3 feet away return into the boiler.

    I think we've been targeting that sharpie maker mark around 40% up the sight glass, so if there's no harm in aiming for 10% higher up the glass, we can try that at 50% up the glass. What happens if we overdo it a bit and keep it running at 60-70% up the glass over time with a few extra gallons of water in the WMC EG75 boiler?