Sunvic sunstat wiring

I'm tearing my hair out with the installation of this thermostat. I thought it would be a simple job although the manufacturers instructions aren't clear - at least not to me - about the connections to be made. It has three terminals: com/no/nc. My old stat had a red wire which I assume is live, a yellow which I take as switched live, and blue I take as neutral. I've connected the red to com, yellow to no, and isolated the blue. The stat doesn't respond to the programme timings or temps. Neither does it fire up on manual override. Clearly some connection is wrong as when I put the stat off (into frost protection mode) the stat clicks and the boiler fires. Otherwise nothing. I just can't see how a live com and no connection can provide power when the unit is switched off! Any ideas what I've done wrong?

Any suggestions other that getting an engineer in gratefully received.

Cheers

Steve

 

Hi yes I've tried it both ways and neither work..... I might swap them over again tomorrow. At least the hearings on even though the stat is switched off!

 

Damn. Yellows live! Guess it shows never to rely on wire colour. It's working fine with yellow-com and red-nc......go figure.

 

Oh-oh. Spoke too soon. After a lot of faffing about it turns out that the new stat was faulty. So as an update for anyone else trying a diy installation of this stat: connections are live to com and switched live to N/O. Neutral is isolated. Replacement is in and working fine. The faulty one was only intermittently showing a temperature reading and when it did (when disconnected from the mains power) it was around 10deg below the true room temp and fluctuated wildly. Maybe it should have been obvious that the stat should have presented a temp but the instructions do not say anything about the display and icons. It would have helped if they had been clearer.

 

Neutrals always been isolated.