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

  1. #1
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    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, (http://nl.documents1.nefit.nl/sitema.../id/6720806207)
    and seems to work with Junckers boilers (and Nest here https://carly.be/using-the-nest-ther...kers-boiler-2/)

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

    Thanks,
    Marcin

  2. #2
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    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 (http://otgw.tclcode.com), 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: https://www.worcester-bosch.co.uk/pr...instructions-1

    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.

    David.

  3. #3
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    An update on my previous post...

    Although my installation worked, I was disappointed with the performance. I expected more boiler run time at lower output as the system modulated, but instead it seemed to switch the boiler on and off more frequently than the conventional relay-driven control. I tried to find a fault but couldn't. Room temperature control was OK, but in the end I reverted to relay control as I was concerned the number of boiler starts might cause premature failure and I didn't have time to mess about with it. I meant to come back to it, but we then moved away.

    As mentioned before, I built an Opentherm gateway - http://otgw.tclcode.com/ - and found it quite useful in monitoring the messages back and forth across the Opentherm network. My next step was going to be to tweak the voltage level at which the gateway triggered to see if the signal from the bridge was hovering around the trigger level and causing false starts.

    My current boiler does not support Opentherm. When the time comes to replace it I plan to have another go, but may go for a more OT-friendly brand.

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