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Boiler and system circulator coming on before valve opens

Pineridge
Pineridge Member Posts: 2
in Radiant Heating
I put a new ZVC405 on my 5 zone with priority on my radiant system. The main circulator and boiler fires as soon as heat is called by the thermostat before the actuator opens. The causes a hammering in the pipes till the valve fully opens. Do I need to put a switching relay of some kind of delay timer to eliminate this problem.

Comments

  • hot_rod
    hot_rod Member Posts: 23,404
    Do you have thermal actuators with end switches? Unless an end switch connection is jumped, the valve end switch should call on the circulator?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Pineridge
    Pineridge Member Posts: 2
    hot_rod, the actuators are wired as they were originally, 2 wires with the end in controller unit looped 3&4. The actuators do have 4 wires which I assume was for the end switch but they had them snipped off, not sure why.
  • hot_rod
    hot_rod Member Posts: 23,404
    The end switch wires need to be connected to allow it to work properly, the pumps should wait until the valves are open, at least partially, before any circulators start spinning.

    With jumpers as you indicated, yes the pumps will start as soon as the T-stat calls any zone on, not ideal :)

    There are some relays that work on time delay instead of end switch closure, I don't know that that model has that feature?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream

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