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Thread: Worcester Bosch and Opentherm (again) maybe Evohome?

  1. #1
    Automated Home Lurker
    Join Date
    Jan 2018

    Default Worcester Bosch and Opentherm (again) maybe Evohome?

    Hello all,

    It appears that W-B may not be that much against Opentherm after all.
    EMS to OpenTherm Converter exists under part no. 7 746 901 847

    It seems to be originating from Nefit brand, (
    and seems to work with Junckers boilers (and Nest here

    So - has anyone tried it with UK W-B branded boilers?
    Or Opentherm / Evohome?


  2. #2
    Automated Home Lurker
    Join Date
    Dec 2017


    Hi Marcin,

    I've tried this, using the Nefit converter, a WB Greenstar 24i System boiler and the Honeywell Evohome system. I only connected it up today so can't comment on any efficiency savings, but the converter seems to work perfectly.

    I have an Opentherm Gateway connected (, which shows the system swapping Opentherm messages and modulating the boiler according to heat demand.

    If you're connecting up a similar system, note that you need to put a wire link between the Live output from the boiler and the switched Live return, as originally shipped with the boiler and as advised on page 6 of the WB Wave thermostat installation manual here:

    With the weather as it is I don't expect to be running my boiler much at the moment, but as the system also heats the hot water I'll keep an eye out for any problems.


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