Cable for wiring nest thermostat

Has anybody had to run new wiring for a nest thermostat or similar?
What type of cables did you use?
Where did you get them?

Nest recommend the following

Stranded wires

The Nest Learning Thermostat does not support stranded wires.

If your low voltage wires are stranded (each of the low voltage wires is made up of lots of smaller wires), you may run into this error. Reinstall your previous thermostat and contact a Nest Pro installer to have your thermostat wiring replaced or adapted to work with the Nest Learning Thermostat.

The Nest Learning Thermostat wire connectors require 18-22 gauge solid-core copper wires.

Wires are too small

The Nest Thermostat might not sense your wiring if the wires for your heating and cooling system are too thin. The Nest Thermostat requires wires between 22 and 18-gauge, which is standard for residential heating and cooling systems. Anything smaller than 22-gauge wire could be too thin for the Nest Thermostat to detect.

If you aren’t comfortable replacing the low voltage wiring in your system yourself, contact your local HVAC professional for help replacing these wires.


  • +1 vote

    Hey mate no idea about your product but the wire you want is probably bell wire or similiar. It is low voltage wire that is single strand.

    This wire is 21 AWG (American wire gauge) So it should work. Its sold at Bunnings by the meter.

    They should also have a heavier duty single strand wire but it may not fit in the terminal.


    Cheers, I'll check it out.


    Worth reviewing this page here, with the main message being that most old thermostat 2-core cables are not Nest compatible.

    At a minimum you'll need a three core wire to operate just a heater or a five core if heater/cooler. Jaycar sells stuff by the meter or in spools for both trailers and home security systems. AWG or weights are not consistently listed on their products online, but something like this would probably do the trick.

    Depending on how your thermostat is wired at the moment it may be possible to drag through a string line with the old wires, then drag through the heavier cable. May also be worth getting a sparkie in to help given how much of a pain running cables is.

    Have you bought a Nest yet? Have been looking for my folks, but yet to find a good shipped-to-Australia bargain.

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