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Weil-McLain boiler / steam - hydronic loop stopped working

axele Member Posts: 2
We have a single pipe steam system. Works like a charm.

However the hydronic loop that is on a different thermostat stopped working. I can feel the pump turn
on when the thermostat turns on the the loop system. But there is not warm water circulating and the boiler
seems to be doing nothing.

Any pointers to what might be causing this ?


  • Jamie Hall
    Jamie Hall Member Posts: 23,635
    I see an expansion tank, so do I assume that this is a closed hot water system, not using the boiler water? How is the hot water system heated? Heat exchanger? Using the domestic hot water coil in the boiler?

    And if it is a closed system, what is the pressure in the system when it is cool?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mattmia2
    mattmia2 Member Posts: 9,941
    I see a prv as well, but I don't see a pressure gauge so I'm not sure how you are supposed to check/set the pressure. Is there a gauge on this loop somewhere? It looks like it is using a tankless coil as the HX but I don't see the return clearly.