Nest thermostat in Australia for in floor heating at 240V

Been wanting to use Nest thermostat in Australia since it came out, however it is focussed on 24V in the US, and cannot switch 240V.

However since Nest went to the UK - the company released a product that comes with the base package called Heatlink that will switch 240V up to 3Amps. The good news is that now I can use it to replace my Amuheat AT8V thermostat.

The bad news was that the Amuheat AT8V thermostat, switches 240V and 16Amps, so I needed to work out how to make the Nest Heatlink switch 16Amps. I little investigation, and some thought, and a trip to Jaycar, and here we have the solution below:

1. 240V 15Amp relay, that is switched by the Heatlink

2. A 15Amp fuse and a 3Amp fuse to protect both the new relay and the Heatlink

3. A circuit diagram below that I installed - see below Heatlink connections with a 3Amp fuse, and the 240V 16Amp relay with a 16Amp fuse. There are 2 loads switching in my system, when the Heatlink is turned on my my UK Nest thermostat.

Note: I will not provide detailed instructions, because if you do not understand the diagram above, and how to buy the right components and install it, then you should be getting an electrician to do it for you.

Anyway, we now have a Nest setup, running my in-floor water radiant heating, and it is learning as we speak and starting to save me money. e.g. Previously we had the heating running from 4pm in the afternoon to 8pm everyday. Now the Nest is working out when people are in the house, on a day to day basis, and turning the heat off at 7pm, because it knows that it takes over 2 hours for the temperature to drop way below 22 degrees.

Love it.