Needs Help to Install Nest Thermostat 3.0.

Hi fellow OZBargainer

I have purchased Nest Thermostat 3. I thought it could be easy to install with all those videos on Youtube. But seems it's an American product so the wiring looks like American standards too.

Anyway does anybody can help me with a guide to install. I have Brivis Gas Heating with 2 Grey wires.

Thanks in advance

Please find my Thermostat Pics


  • The two grey wires are most likely just switched on and off by the relay on your old thermostat. They appear to be low voltage.

    HOWEVER, this may not be the case. Proceed at your own risk. If you have a multimeter, you can easily check.

    I believe that you need to connect your grey wires to the Rh (red heating)and W1 terminals on the nest. It doesn't matter which grey wire you connect to which Nest terminal.

    • Thanks. Somebody who have already install might have a greater idea.

      • I think your chances of finding someone with your exact combination is quite low. If you don't have a multimeter or the skills to use one, then you need to find someone who does. Sorry.

        If my first sentence is true, and it's the most likely arrangement of the Brivis, then my third sentence will also be true.

        • I don’t see how it can be powered to function, the installed thermostat clearly has the display powered by a battery.
          OP, what did the compatibility checker say when you ran it:

        • From the nest web site:

          "While we find that in the vast majority of homes the Nest thermostat can charge its built-in battery using the heating and cooling wires, there are a small number of heating and cooling systems and situations where the Nest Thermostat may require a common wire to bring power to the thermostat."

          Seems that they try to draw power from the relay circuit, and that may or may not work in the OP's circumstances.

      • Hey, did you ever get this sorted out? I have the same setup and have been trying to figure out if the two grey wires will power a Smart Thermostat

  • Lol. There are 2 wires and you are unsure. What do you think is going to happen?
    BTW - when I looked at the nest a few years ago it needed active power to operate. Did you check it was compatible before purchase?

  • Read whats on the old board and what is on the new board and see if they match? Should be small writing indicating what does what or at least a code? Can you trace the traces? See what cables run to what? Download the schematics?

    I am sure USA still has a colour code that is similar to ours? Grey may be data or low voltage DC?

  • Just hire an electrician to install it. You clearly don't know what you're doing so I wouldn't be messing around with electrical wiring if i was you. 230V means that you don't get a second chance if you make a mistake.

  • +3

    Piece of cake to install. You don’t even need to be qualified as you’re working with low voltage.

    The Nest needs a 24VAC power supply to operate with two wire systems properly.

    First of all, turn off the power to the heating unit in the ceiling.

    I bought an adapter from JayCar along with some wirenuts from Bunnings as well as some electrical wire. Join the naked/stripped AC adaptor wires to the electrical cable, run it from the ceiling down your cavity to where the thermostat wires come through, connect to the Nest terminal block (C terminal and Rc terminal - active and neutral placement doesnt matter, just use whatever you want).
    Your existing two Grey wires you want to plug into the W1 and Rh terminals on the Nest terminal block.

    Once you’ve done that, switch on the new 24VAC adapter and turn the power to the heater unit and you’re done.

    • Great helpful comment.

  • Nest's installation has been very tricky and challenging on my end as well!! I read further details about it which eventually helped me. If it wasn't for the energy saving, i wouldn't opt to nest, i would have chosen honeywell.

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