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Thread: which cable to use for opentherm

  1. #1
    Automated Home Lurker
    Join Date
    Oct 2017

    Default which cable to use for opentherm

    Can someone please suggest which cable to use to connect a boiler to the opentherm bridge?

    On another forum it was suggested using speaker wire. This one

    But I was thinking that it should be at least heat resistant and permanent, so something like this

    THe boiler is going in the loft and the bridge may need to go on the floor below to get a good signal so the cable length maybe several meters.


  2. #2
    Automated Home Guru
    Join Date
    Feb 2016



    I agree with your second cable choice with an outer insulator for permanent installation. I've played around with different low voltage controls for my boiler and now use the Honeywell Opentherm Bridge. The only wiring recommendations I'm aware of are ensuring that the cable run is kept away from 240V cables to avoid interference (some of my controls even came with ferrite cores attached to their cables) and keeping the overall resistance of each conductor to a maximum of 5 Ohms. Hence, I've chosen to use a 0.5mm2 conductor cable for runs 5m or more similar to the one you've linked. There's no problem with using a larger diameter conductors, if you have other cable lying around as it will have an even lower resistance.


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