So should I fit a nest thermostat myself?

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  • So should I fit a nest thermostat myself?
  • Premier Icon MikeG

    I fitted ours, was some variety of wireless thermostat before and only had 3 wires – took about 20mins and worked first time 🙂


    I don’t have a nest but I did fit the wireless thermo and it’s just sticking in the correct wires…I’m doing this from memory but the key is having your boiler manual (downloaded from internet)

    You want your boiler manual as these are either a small DC switched or mains and some boilers have both.… The Hive I’d guess wants the
    low voltage DC one so you’d likely fry it connected to the wrong one…

    A decent modern boiler probably only has low voltage…. I have a reasonably modern boiler but its crap!

    However, your existing Wireless is almost certainly low voltage DC (but worth checking) so it should be a straight swap. If it plugs in on the boiler side of the wireless then even more likely its low voltage DC….


    We have Tado and the supporting instructions were excellent. They didn’t initially have our boiler model but within an hour they’d emailed detailed drawings showing how to wire things up.
    Get onto the nest website to see if there’s anything similar.


    Current thermostat is a rt500f

    Wireless Programmable Room Thermostat – 868MHz

    Radio frequency digital programmable room thermostat with large backlit LCD display.

    Thermostat: 2x AA Batteries
    Receiver: 230Vac 50Hz
    Rating Max: 16 (5) A SPST
    Output: 0 – 230V
    Scale: 5 – 35°C
    Size RT500: W-130 H-95 D-40
    Size Receiver: W-130 H-95 D-65
    L – Live
    N – Neutral
    COM – Live in
    NO – Switched output

    Volt free contacts
    5/2 or 7 day programming flexibility
    60 metre transmitter range
    Desk stand
    Frequency 868 MHz


    So looks like the receiver runs of mains.

    Would there be any reason I might need to adjust the boiler? I can’t see why in effect I just want to replace the switch….so it should be live, neutral and the on/off line


    So looks like the receiver runs of mains.

    Yes but if that is supplied via a plug then the switching will still be low voltage DC.

    I think its really only older stuff (pre-wireless) where they use mains voltage to run a thermostat or external timer direct from the boiler mains power…

    There will be a wiring diagram for your boiler and this indicates if it is mains/low voltage DC or both…. and which pins the wires are connected to,

    From memory mine has both but like I say it’s a crap boiler not a Vaillant!


    £79 to get someone in.

    Already have a wireless salus thermostat on a valiant combi Haven’t opened it up yet but from what I can tell it will be 3 wires.

    If I read the nest manual right it should be a matter of rewiring those 3 wires into the appropriate terminal on the heatlink

    Consequences of failure would be a highly irate pregnant wife.

    Worth having a go? Anyone wired one up themselves?


    When I fitted my Hive it was the same back plate and the same pins – they are industry standard for the most part. Remove old receiver, install new one, job done.
    They will have a wiring diagram, just turn off the mains to the boiler before you start, two screws at the bottom of the receiver and it lists off. No need to open up the boiler as the old receiver probably says what the pins are on the back 🙂


    Well job jobbed with my 2 year old ‘helping’. Longest part of the process was setting the initial schedule….

    Slightly more successful than my bathroom cabinent fail

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