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Thread: Adding unvented cylinder to combi?

  1. #11
    Automated Home Legend
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    I have confused your thread sorry. You were asking if an unvented cylinder could be placed after the boiler. This is the normal configuration. And Evohome will work for you.

    What I was saying is that, if you had solar, wanted a combi but felt the combi was not enough for simultaneous showers then an unvented could be placed before the combi. This unvented would be preheated by solar.
    The combi then potentially could get a 60C inlet, and has to do very little work to top up the heat. So could still be sufficient

  2. #12

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    Quote Originally Posted by bruce_miranda View Post
    I had no idea that some combis could even work with a 60C inlet feed. But apparently Intergas etc are happy with that.
    Intergas certainly opens up options, I've toyed with a cylinder as you described, but also with a coil taking the CH return into the boiler to further increase the change of the boiler condensing, whilst pre-heating the DHW.

    There's the installation manual for pre heated water by solar.

  3. #13

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    Details of per-heated solar DHW on an intergas boiler
    Screenshot 2021-03-23 at 18.56.56.jpg

  4. #14
    Automated Home Ninja
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    If you have an Unvented cylinder you will require a cable back to the zone valve. You cannot just use the Hot Water Kit to control the zone valve.

    The Cylinder High Limit stat is still required to bring it up to regulations, a fail safe device. To utilise this you'll need a cable back to cut the power the zone valve should an overheat situation occur.

    You must use the high limit stat, so your installer is correct.

  5. #15
    Automated Home Guru
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    Quote Originally Posted by mtmcgavock View Post
    If you have an Unvented cylinder you will require a cable back to the zone valve. You cannot just use the Hot Water Kit to control the zone valve.

    The Cylinder High Limit stat is still required to bring it up to regulations, a fail safe device. To utilise this you'll need a cable back to cut the power the zone valve should an overheat situation occur.

    You must use the high limit stat, so your installer is correct.
    The installer was indicating a cable needed to run from the zone valve to control the boiler.

    What you describe doesn’t require a cable back to the boiler, I think just wiring the high limit stat in series between the DHW BDR91 output and the DHW zone valve.

  6. #16
    Automated Home Ninja
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    Quote Originally Posted by kevinsmart View Post
    The installer was indicating a cable needed to run from the zone valve to control the boiler.

    What you describe doesn’t require a cable back to the boiler, I think just wiring the high limit stat in series between the DHW BDR91 output and the DHW zone valve.
    Yeah, that's what I said. A cable back to the zone valve.

    This is obviously dependant where your zone valve is.

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