Vaillant heat pump relay

[vaillantheatpump]

I have a vaillant heat pump for my DHW and underfloor heating. The underfloor heating is controlled by Heatmiser thermostats with a UHF-8 wiring centre. I've just upgraded the heat pump controller from a VRC700 to a VRC720 (sensocomfort).

Now, whenever the heating is "off" on the thermostats, the heat pump is active and showing a radiator icon on it. Similarly when the underfloor heating is turned on with the thermostats, there is no call on the heat pump.

I've spoken to Vaillant and they have told me that the VRC700 and VRC720 process the call signal from the UFH in opposing manners (signal=on vs signal=off), and that I can either get a VR71 or put in a relay. I don't particularly want to spring ~£250 for a VR71 wiring centre but I'm unsure exactly what to look for when it comes to choosing a relay.

Any information or help would be appreciated. Thanks.

 

[Harry Bloomfield]

I don't particularly want to spring ~£250 for a VR71 wiring centre but I'm unsure exactly what to look for when it comes to choosing a relay.

That should be simple enough, given enough information. What voltage, ac or dc, and current is powering the coil of the relay, and what current and voltage does the relay need to switch? Do you perhaps have a circuit diagram, which shows how this relay is installed?

 

[vaillantheatpump]

Turns out I don't need a relay after all.

For anyone finding this in the future - I looked at the wiring going from the vaillant hardware to the heating manifold hardware (uf8 rf) and where it connected to the UF8 rf there were ports for C, NO and NC. I moved the wire from normally open to normally closed and that sorted me.