Nest Learning Thermostat 2nd generation: UPDATE : electric boiler to enable external control of heating stages

I had to hack into my electric boiler to enable external control of heating stages. Originaly it was controled manualy by micro switches on the boiler. Solution : bridge the switches with relays :

Since I have now 2 branches of the heating (Ground and 1st floor), I integrated 2nd (not Nest) thermostat on 1st floor, heatpipe valves and timer relays. Since the boiler
runs the water pump for 4 minutes after shutting down the heating, heatpipe valve must close 5 minutes after boiler off command

I also made wiring diagram of the final version of Nest < = > Boiler interface :

Final version :

Used equipment :
Circuit breaker : ETIMAT 10 B 1p 10kA 6A
Power source : ELKO ZSR-30
Relays : ELKO VS116K
Timer relays : ELKO CRM-91H

1 comment:

Anonymous2/24/2015

Marvelous! Well done!
Nevertheless I’ll keep on waiting until Nest comes up with a version that supports modulating heaters. It still doesn’t feel right to me to let the heater burn at full power, while shimmering will suffice…
Furthermore my heater has a built in tap water boiler that’s managed by my old thermostat as well (i.e. during the night it’s not heating tapwater). That should be handled by the next Nest as well…

I’m just not geeky enough to make a script to handle all that (if at all possible).