Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Curious about Cause of Flooded Steam Boiler

PaulVndrWd Member Posts: 3
edited January 2018 in Strictly Steam

This fall we installed a Weil-McLain LGB-7 steam boiler. We used a McDonnell Miller #150S level control connected to a duplex boiler feed tank. (We only run one pump at a time.) The boiler was cleaned, skimmed, and then maintained with Romar 903 chemicals. All was well, until...

The other day we received a no heat call from the boiler owner. When I got there, the boiler feed pump was running non-stop. The system was flooded.

I shut off the power to the pump and water gushed out of the overflow as expected. I took the cover off of the MM150. Everything was normal. The float was up. There was no continuity through the switch. The pump was within the specifications of the switch.

This system has 2 - 4" zone valves. My questions are these: Is it possible to air lock the float chamber of the 150, even if it's properly piped? Could a vacuum from the zone valves have affected the float?

Curious to find an answer.


    EBEBRATT-Ed Member Posts: 15,605
    Can't see the 150 piping on top of the control but as long as you haven't piped a trap in the top pipe you should be ok.

    I would double check the wiring. The only 150s I ever had trouble with were the old mercury switch type. I did have one of those that kept running the pump for no reason, float was good. switch seemed good. You probably have the newer type switch.

    Just have to try it and see