I've just installed a nest 3rd generation and initially just connected up the hot water. The system is on a canal boat so easy to wire the 'call for heat' from the Webasto heater to either of the 2 relays (heating or hot water) on the heat link.
FIrst 2 days it worked great with the hot water schedule closing the relay in the heat link and providing 12V to the webasto call for heat.
Today however the webasto fired up on its own. I checked the heat link and the relay for the hot water had turned on ie pins 5 & 6 connected. I couldnt turn it off from the thermostat or from the app. Even turning the hot water off in the app did not open the relay. I disconnected the call for heat wire from the webasto - so it stopped heating.
I then tried to turn the heat link off and on. After turning it back on, the relay was not energised but after circa a minute the relay turned on on its own - even though the app is set for hot water off and no schedule to be on in the water heater schedule. Every time I power up the heat link it powers up the hot water relay. I dont think it is anything to do with the webasto as the heat link is no longer connected to it.
The heating relay seems to be pefroming correctly.
Any ideas? What am I missing
