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Power Usage of Zone Relays and Relay Switches

Hi, I posted this in the Radiant Forum, but didn't get a response on this part, this is probably a better forum for it.

Does anyone know what the power usage of a Taco one zone switched relay is? Probably similar to a single zone control. A Taco guy is telling me it draws 20W when powering stuff, but only enough for the LED (less than 10 ma) when there is no call for heat. I assume this is untrue since the transformer draws a significant amount of power at all times (and is pretty darn warm to the touch). I would guess this draws close to 20W at all times - 24x7x365. Does anyone know? Or do I have to run it through a meter to find out?

As pumps are getting more efficient, what are you guys doing for zone controls and switching relays to conserve power on that end? If my guess is correct, this single relay will draw $300 worth of power in its 15 years of life.


  • Tim McElwain
    Tim McElwain Member Posts: 4,445
    If it has a 20 VA transformer

    that is 20 watts power that is available. However all the transformer in the relay is for is to operate the electromagnet to bring in the clappers on the relay and a very small amount for the LED. Therefore it would depend on the cycling process as to how much would actually be used.
  • ChasMan
    ChasMan Member Posts: 459
    Not 10 watts.

    The holding current for an ice cube relay is normally less than 2 watts. Taco's statement of 10 seems a little high.
  • LazyDevil
    LazyDevil Member Posts: 5
    edited November 2011
    Quite Low Power

    Looking at the date of your post, you probably have found the answer; but in case anyone reading this thread is wondering:

    Just put a meter on a Taco SR501 Single Zone Control and it draws 2 watts with a power factor of 0.19 with the relay open. When the relay is closed the the draw rises to 4 watts with a power factor of 0.32, both readings seem quite energy efficient to me.

    Albany Chris
This discussion has been closed.


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