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Thread: Intergas HRE 18 SB+Opentherm bridge+Outdoor sensor impression

  1. #1
    Automated Home Lurker
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    Feb 2017
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    Default Intergas HRE 18 SB+Opentherm bridge+Outdoor sensor impression

    Hello guys.
    Just a feedback here which might be useful and some input from others could help as well. As my 12 old years old Promax 15 HE pretty much packed up totally on December I decided to change boiler to a new which would support my full Evohome S plan via opentherm protocol. After reading a lot of (many thanks to Hengus for a lot of feedback) I decided to give a go with Intergas despite 'some issues' - trusting theevohomeshop that intergas boilers will modulate with opentherm demand. I also want to point out that Intergas UK technical department said overphone that Intergas boilers wont work with multizone evohome.
    1. S Plan has been modified with CH valve normally on and energised off in series with HW valve obtaining HW priority as guided.
    At this point boiler is controlled entirely via opentherm bridge, ie HW BDR controls valves (HW ON+CH OFF) only-and Im not sure this is the best way to reheat cylinder-it takes longer and my question is wether I should use S/L from HW BDR in addition to openterm to obtain better HW control - can anyone explain this?
    2. I did obtain intergas cable and IDS software and it looks like boiler indeed modulates down temp flow (manually limited to 75 on boiler). Boiler spends most of the time pumping heat around (especially overnight when only 1 radiator in master bedroom is set to 19 degrees).
    3. Intergas in manual states that boiler can work with opentherm bridge AND weather compensation (outdoor/outside) sensor. It does not clarify the way it should work, however it was my impression that depending on outside temperature boiler would limit further temp flow. I left parameters as per examples in chart in manual and with 5 degrees outside it should limit max temp flow to around 65 degrees (I also checked ntc resistance and is fine). That however does not work - temp flow remains at 75 when at max demand and modulates down as zones gets to expected temps. Any ideas how that meant to work?
    Many thanks,
    Jack

  2. #2
    Automated Home Legend
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    Jul 2014
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    I have a Vaillant, but I just can't see how OT and outdoor weather compensation can work together. Both of them are trying to alter the max flow temperature to satisfy themselves, surely one will loose. I know on the Vaillants there is an eBUS hierarchy that stops multiple thermostats on the bus. So the OT isn't even allowed to communicate if another weather compensation control is seen.

  3. #3
    Automated Home Ninja Dan_Robinson's Avatar
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    Jun 2012
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    It depends on the controller.

    If a weather sensor is present, that data is fed to the controller and the data used. Or not.

    In the case of Evohome, it is not used.

    Some controllers use it to help with trimming the flow temperature or enhancing any optimisation.

    The extra benefits of this are marginal.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

  4. #4
    Automated Home Sr Member
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    Apr 2017
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    Weather compensation puts an upper limit on the flow temperature in relation to the current outdoor temperature and how the system is setup for the building. If Evohome were to use this feature, then overshoots would surely be reduced or eliminated when there's a demand from a room that is below Evohome's narrow proportional band.

    I don't have Evohome, but I do have an Intergas boiler with OpenTherm & weather compensation and the two work together beautifully.


    Martin.

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