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Taco SR-503 and ZVC-406 Daisy Chained?

I've got a Series 2 Burnham boiler with three circulator zones controlled by a Taco SR503 switching relay and new 007e circulators. I've added staple-up Side-trac radiant floor system with a Grundfoss Alpha pump and a diverter valve for temperature regulation.

Right now I've got all zones of the radiant floor open and I just run the pump continuously. When the the circulator zones call for heat, the radiant floors get the right temp water and feel great. When there is no call for heat from the circulators, the floor doesn't warm up.

I have a Taco ZVC-406 for the radiant floor zones and a Hydronic Alternatives 2-stage setpoint controller that I'd like to tie into the boiler so the boiler can cycle on when the floor temp is below a setpoint. The plan is for the pump to run continuously through at least one radiant zone while the outside air temp is below 60 and then to use the floor temp and a couple thermostats to call the boiler.


Any guidance on the best way to wire the setpoint controller and ZVC to the boiler or existing switching relay?


  • Teemok
    Teemok Member, Email Confirmation Posts: 478
    Why constant circ. if there's not heat available to it. I would think the floor min sensor should activate both boiler and all zones till it hits set point. Balancing flow to floor mass would be important. The mixer sets floor supply temp. I'm not sure the two stage control gets you much but I don't know your system. The floor set point control could close 3 dpst relays that connects all the ZVC's 6 t-stat zones by sending an R to all the W's. When the set point control opens the relays the set points W's are all isolated and control is given up to the normal t-stats.