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Quick Taco SR502 Switching Relay questions

Question #1: The 6 amp fuses, it's in series with what?
Question #2: What does ZR and ZC do and how does a jumper affect operation?

New tech still learning, thanks.


  • GW
    GW Member Posts: 4,679
    6 amp, the whole control I presume

    ZC-–------, so if there's ever a time when you don't want the zone pumps to run, you drop that jumper between ZR and ZC.

    So if your boiler has a pump output just grab the hot leg of that terminal and stick it on the ZC.

    Now the boiler control allows the heat pumps to come on.

    This is done when you have a dhw indirect or a low water temp issue you're trying to deal with
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • newagedawn
    newagedawn Member Posts: 586
    really dont need zr zc, just use tt from aqua stat to xx in the control that should turn boiler on when needed and the t stats will run the 2 zones when calling for heat, thats all you need
    "The bitter taste of a poor install lasts far longer than the JOY of the lowest price"
  • lchmb
    lchmb Member Posts: 2,997
    There should be a fuse for each circ. The zc and zr can be used if you have two power sources to keep them from butting heads inside the box. They can also be used to call a boiler on prior to a circulator in the case of a cold start boiler. You dont want to start pulling heat back out of an indirect to heat a cold boiler...