Viessmann vitodens 0-50w, Google Nest & Opentherm problem

[k00ba83]

Hi.
I'm new here.
I've purchased Google Nest 3rd Generation learning thermostat and engineer came yesterday to install it. Live + neutral from Heatlink connected to boilers live & neutral, then OT1 and OT2 connected to the block on top of the electric board (pin 3 & 4) (see image- not mine, but I've marked what's connected where). Commissioning C.7 changed to 14 (opentherm) and... error 95 on the boiler- "OpenTherm remote control unit not connected". On the Nest controller also error when setting up and reaching boiler selection (H73). He tried it with and without bridging the on/off switch in the boiler. Any ideas? Thanks!

 

[sweetbeans]

Any luck with this? I am having same problem.

 

[k00ba83]

I've ended up calling viessmann and they send an engineer for a repair. Turned out one of the cables in the area marked on the photo was not inserted all the way in, must have been accidentally pulled out by the first engineer when he was feeding the cables to the thermostat. So make sure ALL cables are fully inserted, maybe it's as simple as that.

 

[sweetbeans]

Ah thanks a lot, I'll have a look.