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Thread: Can I wire a Taco 503SR and a 504ZVC together

  1. #1
    Larry Matteson

    Default Can I wire a Taco 503SR and a 504ZVC together

    I have an oil fired hot water boiler that has a tankless coil. It has 4 circulators 3 of them control one zone each and the 4th controls a line with multiple zone heads. I'm not sure of the tt wiring from the triple aquastat to the 2 taco controls and how the 2 controls shouyld or can be tied together?
    Can someone help?:

  2. #2
    DIY Senior Member CHH's Avatar
    Join Date
    May 2007
    Denver, CO


    You've got to keep the boiler hot in order for the coil to deliver hot water. Does that tell you that the aquastat controls the boiler and the thermostats control the circulators?

    I don't know a thing about the Taco products you mention but function follows control. Whatever you want the device to do (boiler or zone in this case) the the control has to force that function.

  3. #3


    You do not need a ZVC...use a SR 504,not a 503....wire the 3 thermostats and circulators to the relay as the instructions show......now in place of the ZVC get a 24volt,40va transformer and wire like this....from the R terminal on the 24 volt side of the transformer go to each R terminal of the thermostat on the zones controlled by the zone valves,from the W terminal on the t-stat back to one yellow wire on the corrosponding zone valve,the other yellows go back to C terminal on the transformer,take one red wire from each zone valve,tie them together and they go to one thermostat terminal on the SR 504,same goes for the other set of reds..(I am assuming that the zone valves are Honeywell v8043 e's........if not, then you will have to figure out which wires are for the zone valve motor,yellows on the Honeywell,and which are the end switch)the circulator for the zone valves gets wired to the zone that has the zone valves on the 504...........XX to TT on your aquastat and there you go!!

  4. #4
    Larry Matteson


    Got it .




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