Installing 2 Google Nest Thermostats v3 in a multi zone system

[Dionisus444]

Hi everyone,

I need some help. In our house we have a multi zone sytem. Downstairs we have underfloor heating. We have radiators upstairs. These are also our 2 zones. In this way we can operate the downstairs and upstairs completely separately from each other with 2 thermostats. The thermostats are from Honeywell. Each zone uses an electric zone valve, namely the Honeywell vc8615. One thermostat is wired, the other one is wire free and is connecting to the zone valve with a Honeywell BDR91. The central heating boiler is an Intergas Kombi Kompakt HRE.

We wish to replace the two Honewell thermostats with 2 Google Nest Thermostats. The question is: how do I connect the Heat Links? I already contacted a elektricien but he said it's not possible and advised to replace everything with products from Tado. But in the manual and on the website of Google I read that it should be possible to use 2 Google Nests Thermostats in a multi zone system.

The question is: how can I wire the Heat Links in our set up?

Some pictures:

Regards,

Dennis

[Frustratedddd]

The simple and quick answer is yes you can connect 2 Nest thermostats to your original system. The problem is without being there connections are hard to imagine, if you get where I am coming from.

A Nest thermostat is nothing but a thermostatic switch, same as your current thermostats, but more fancy!!! Yes it has a Heat Link, but that's just a box for connecting 240v here in the UK.

However, you say you have 2 thermostats installed currently, in that case the instal should be pretty simple. The Thermostat/Heat Link is just a switch, exactly the same as your current thermostat. When connected from display to Heat Link the terminals 3&4 are all you will require for the switching. You will need 240v at the Heat Link, but that shouldn't be an issue.

Assuming your current thermostat is 240v, and connected direct to your system, then the Nest would be as simple as following the connections.

I think you need an electrician that knows his stuff.

[Dionisus444]

Thanks for this answer! The elektricien somehow ovelooked our 2 motorized valves with transformer from Honeywell. He replied that it will indeed be possible to install the Google Thermostats. He is coming back this week to install the heat links.