Replacing Danfoss 230v thermostat and FP720 controller with nest heat link and thermostat.

[Bainn41]

Hi

I’m trying to replace my thermostat and heat controller, but I’ve several issues.

1. My thermostat is fed directly with 230 V.
2. The grey DHW cable doesn’t lead into my boiler (it’s cut) but I still have access to hot water

So my question is. If I’m installing my nest how do I power my thermostat without blowing up. And I’m not sure what cables terminate were within the heat link. All photos attached show my boiler connections and my old thermostat and heat controller.

 

[ericmark]

As far as I am aware Bosch does not do OpenTherm so no real advantage using Nest, but since Nest has volt free contacts on/off control can clearly be done, I assume you want Nest Gen 3 if doing DHW as well, however not sure if that boiler is a combi boiler or not, may be reason you can't trace DHW is that it is not direct?

 

[Bainn41]

Thanks for the reply. this is a system boiler. I am trying to install the nest 3rd gen learning.

 

[CBW]

If you plan on using the existing thermostat wiring for the Nest thermostat, then you need to wire the heat link near to the wiring center. If you’re going to use a usb cable that it comes with then we can explain how to proceed.