replacing wirsbo tstat with tekmar 519 question

wrxz24

I am trying to replace a Wirsbo radiant tstat with a tekmar 519 with floor sensor.



I only have a 3 wire tstat wire coming from a taco sr506 switching relay to the wall.



Do I need to run an additional wire to the 24v on the relay or is there a way around this?



Thanks in advance

wrxz24

Something like this?

Would this work?