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Over temperature of indirect fired water heater

My system is a SuperStor Contender TSSC-50 fired by a Weil-McLain 468WT Boiler which has the circulator in the return line at the cold side of the furnace. The hot side of the furnace is split: one line goes to the house baseboard heating and the other line goes to the SSC-50 connection marked “Boiler Out”. There is a Taco 571-2 zone valve in the line to the SSC-50. There is a Taco 219 SWETCHEK and a Taco 571-2 zone valve in the line to the baseboard heating. There are no other check or zone valves in the system. The SSC-50 connection marked “Boiler In” is piped to the return from the baseboards and then to the circulator.

My boiler’s Aquastat is set at a hi level of 180F, lo level of 120F, and a diff of 25F. The SSC-50 temp level is set to the minimum. The water temperature from the SSC-50’s relief valve is 153F.

Why is the water temperature so hot? Is the plumbing installation correct?


  • icesailor
    icesailor Member Posts: 7,265
    Indirect overheating:

    There is nothing wrong with the piping arrangement with your boiler, heating system and indirect. The problem may be the thermostat/controller on the indirect. That should be controlling the zone valve. The only connection to the boiler control is between #2 and @3 on the zone valve that will start and stop the burner and circulator.

    Set the indirect thermostat/control to 120 degrees or lower. Or, disconnect one wire from the indirect control. The tank should get cold. If it doesn't, the indirect zone valve may be stuck partially open.
  • bill_105
    bill_105 Member Posts: 429
    Just curios

    Why is that Taco 219 there? The zone valve above it will take care of anything that check is supposed to do.

    BTW- That 219 adds the equivalent of 143 L.F of pipe when figuring head loss.

    As for your real hot water, my bet is the ZV. Also, the Taco 571 is probably not the best ZV for an indirect as it is a real slow acting valve
  • kcopp
    kcopp Member Posts: 4,440
    The aquastat...

    on the SSC-50 is bad. I have had issues w/ them in the past. Grab a replacement one for an electric water heater.
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