I need help designing/wiring a circuit for thermostatic relays, which control electrothermic actuators.

Basically I have 4 actuators and thermostatic relays, which pretty much is just a 12vDC JQX-115F SPDT relay that trips whenever heat is needed. This relay switch then supplies 230vAC power to the actuator, which opens the valve in the central heating system. So i have 4 relays and 4 actuators, now, i would like to wire this up so that whenever one (or more) of the actuators is powered on, the central heating circulation pump is powered on and when none of the actuators is powered, the pump is off too.

Initially I thought this would be easy as i could just wire the pump in parallel with the actuators like so:


(2 switches and actuators, because I'm lazy with paint :) ) Obviously this wouldn't work, as any switch will power everything.

So the only other solution I can think of, with my quite limited knowledge of electronics, is using the thermo-relays to switch 12vDC to 12vDC SPST relays, which would switch 230vAC to actuators and pump, and using diodes to make sure each switch only powers on their own actuator and the pump. Like so:

enter image description here

This would work right?

Anyone have a better (cheaper/easier) solution?

Any help/guidance would be deeply appreciated :)


1 Answer 1


Use relays with DPST-NO (2 FORM "A") contacts, with one set of contacts dedicated to a particular actuator and the other set all common to the pump.

  • \$\begingroup\$ Yea, that was one of my original ideas, but since there isn't really room for 2x COM & 2x NO wire terminals on the physical case, I abandoned that idea initially, but since I can't really come up with other alternatives I'm probably gonna just make a shared COM and 2xNO terminals, tho I would have liked to have the option of separate COMs. Oh well, I ordered the parts, so thats gonna be the solution, thanks. \$\endgroup\$
    – Amavin
    Nov 3, 2014 at 13:24

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