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Thread: OpenTherm & Intergas Xclusive Minimum CH Flow Temp

  1. #1
    Automated Home Lurker
    Join Date
    Oct 2017
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    6

    Default OpenTherm & Intergas Xclusive Minimum CH Flow Temp

    Just wondering what others have configured when OpenTherm demand is very low? The Xclusive has a parameter (P057) "Response for OpenTherm room thermostat" with the following options:

    0 = do not respond to heat demand if requested temperature is lower than 30C
    1 = respond to heat demand with minimum flow temperature limited at 30C
    2 = respond to heat demand with maximum set flow temperature (on/off function)

    I'm clear that option 2 is not what I want. I'm currently using the default value but I think this is resulting in a lot of cycling of the boiler as it cannot actually modulate low enough to maintain this temperature, given the very minimal heat differential on the return side when there is only one radiator running with minimal demand. Water is then mostly circulating via the Automatic Bypass Valve (ABV). (I appreciate TPI is the only way to reduce heat output when demand is below the lowest that can be achieved by modulation.)

    Option 0 might be the way to go but I'm not sure what else should be considered...

    P031 ("Maximum capacity of modulating central heating pump") is set to default of 65
    P032 ("Minimum capacity of modulating central heating pump") is set to default of 35
    P033 ("Central heating pump overrun after central heating demand") is set to default of 1 minute
    P034 ("Central heating pump overrun after boiler operation") is set to default of 1 minute

    (I am also confused by the description of P032: "Set 15% of parameter P031", as this does not seem to match up with the default set value in any way I can fathom?)

    In the evening, my current "living" room is the only zone with a demand and it can be as low as 10%. The radiator makes noise every time the boiler fires up (as a consequence of the pump ramping up) and whilst this can probably be improved by tweaking the ABV, it is highly undesirable as the "living" room is actually a bedroom.

    My current feeling is that reducing the minimum flow rate (by altering P032) at low demand might be sensible along with increasing the overrun after boiler operation and/or central heating demand. Hopefully others will be able to steer my thinking more wisely.

  2. #2
    Automated Home Jr Member
    Join Date
    May 2019
    Posts
    23

    Default

    Hello
    I have the same boiler and did quite a lot of changes do to 8mm pipes. The biggest problem i had was lack of heat transfered to rads during low demand.
    I fixed the issue by increasing min pump to 60% i think.
    I ve also changed min flow to 50C and to ignore anything below to avoid frequent power ups.

  3. #3
    Automated Home Legend
    Join Date
    Jan 2015
    Location
    NE UK
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    1,437

    Default

    I have an Intergas Exclusive 36. I left the parameters for OpenTherm at their default settings. Set the maximum flow temperature to 70c and reduced the power of the boiler to 6.4kw. No problems. It works very well. I was concerned at first as sometimes a radiator would feel warm and not hot but checking temperatures all was as it should be. The boiler often shows a running temperature much lower and it bounces up to 70c max if a room calls for heat that was otherwise cold. As expected. I did try dropping the flow temperature to 65c but found it took a little too long to warm a room up.

    My boiler was installed in February last year. Comparing the whole of 2021 with 2020 I used 3814.07 kWhs less gas. The Spring last year was colder than in 2020.

    I also note the ONS in the UK says everybody’s energy bills went up by massive percentages last year (2021). I have no idea how it gets its figures but my gas bill was down last year and electric up by about 2.45%. My prices for gas (net of VAT and standing charge) averaged 2.72p per kWh and for electricity 15.43p per kWh. Even if I add back VAT and the standing charge they are still less than the ONS reports. Makes one question what we are being told.

  4. #4
    Automated Home Legend
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    Jan 2015
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    NE UK
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    Default

    There has been a reply to my above post as I have had an email saying so but it does not appear here. The reply reads:

    “Which parameter did you use to limit the boiler? I used a parameter (something in % that I remember) but not sure if its a correct one”

    The kW rating in the boiler is changed as per the instruction manual. Para 8.5 on page 53 in my manual. For me it is P010 setting 25. That is for the exclusive 30 & 36 boilers.

  5. #5
    Automated Home Jr Member
    Join Date
    May 2019
    Posts
    23

    Default

    Thanks for coming back. I just noticed the setting explanation in the manual.

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