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Constant hot water circulation

I have a boiler 2 zones HW GAS. The 2nd floor zone is constant;u heating up. The T stat is off the flow check is 3/4 sweat on the supply. When I have the customer close the BV at the purge the zone cools. I just can't figure why the flow? There is a tankless. The first floor is operating normal. Hot water is rising up to the 2nd floor but how?
Crazy...going back to check it again (3rd time). Any thoughts?


  • BillAllen
    BillAllen Member Posts: 103
    In addition this is a 2 cir system no ZV's. The circ for the 2nd floor is off (stat even disconnected) with constant flow unless I shut the BV.