Page 9 of 13 FirstFirst ... 45678910111213 LastLast
Results 81 to 90 of 125

Thread: Evohome Opentherm Boiler decision and set up

  1. #81
    Automated Home Jr Member
    Join Date
    Mar 2015
    Posts
    33

    Default

    It's completely conventional Y plan, so at the moment, the boiler is triggered either by the orange wire from the mid pos valve or the B terminal on the DHW BDR.

    So as far as I can see, I still need both BDRs to correctly operate the Mid Pos valve echoing mtmcgavock's advice.

    But this is all getting messy now as I need to add a UFH zone which I'm going to take directly from the boiler flow via a 2 port valve.

    The existing 'heating' BDR - when will it trigger? Only when one or more of the HR97s demand heat? Or will the UFH zone trigger this as well? I suppose it doesn't matter if all the HR97s are closed anyway - all the flow will just go through the UFH zone.

    This whole thing is a mess. I'm annoyed because I only bought the three port valve two weeks ago (the old one failed!).

    At the moment, my Boiler Demand is set to 'None' - that will get set to 'OpenTherm Bridge'?

    This just seems like an invalid configuration to me? Will the original 'heating' BDR still trigger when the HR97's demand heat even when Boiler Demand is set to OpenTherm? This won't 'undo' the previous 'Sundial' config?

    Sorry for all the questions...

  2. #82
    Automated Home Ninja
    Join Date
    Mar 2017
    Posts
    294

    Default

    Quote Originally Posted by stevelup View Post
    It's completely conventional Y plan, so at the moment, the boiler is triggered either by the orange wire from the mid pos valve or the B terminal on the DHW BDR.

    So as far as I can see, I still need both BDRs to correctly operate the Mid Pos valve echoing mtmcgavock's advice.

    But this is all getting messy now as I need to add a UFH zone which I'm going to take directly from the boiler flow via a 2 port valve.

    The existing 'heating' BDR - when will it trigger? Only when one or more of the HR97s demand heat? Or will the UFH zone trigger this as well? I suppose it doesn't matter if all the HR97s are closed anyway - all the flow will just go through the UFH zone.

    This whole thing is a mess. I'm annoyed because I only bought the three port valve two weeks ago (the old one failed!).

    At the moment, my Boiler Demand is set to 'None' - that will get set to 'OpenTherm Bridge'?

    This just seems like an invalid configuration to me? Will the original 'heating' BDR still trigger when the HR97's demand heat even when Boiler Demand is set to OpenTherm? This won't 'undo' the previous 'Sundial' config?

    Sorry for all the questions...
    If your adding a zone on, as I think we've answered before you can't do this with a 3 port valve. The valve needs to be removed. Really all you need to do is replace the 3 port with a single 2 port on the HW circuit as all your rads have HR92s. Then have a 2 port valve for your UFH manifold.

    Boiler Demand will change from none to Opentherm once it is bound.

  3. #83
    Automated Home Jr Member
    Join Date
    Mar 2015
    Posts
    33

    Default

    Got it - thanks.

  4. #84
    Automated Home Jr Member
    Join Date
    Jan 2018
    Posts
    39

    Default

    Hi all!

    So my system was installed in July. Y plan with unvented cylinder, OT via an IS32 Atag, with a normally closed valve on the water side. Full HR92 set up, no satellite room thermostats.

    All seems to be running well, although I am noticing overshoots on my rads, so thinking I need to maybe reduce the max boiler temp which I haven't yet touched.... Visiting this now as my wife is ********, and starting to think about the rads being very hot with a toddler wandering around in the future.

    Other issues, I had my HW set for 7.30-9am bi-daily. Which seemed to be an issue, as the water wasn't heating at all at a time max demand was being requested from the rest of the house. I've sorted this by increasing the window back to 6am-9am which seems to have resolved.

    And finally, the HW thermostat on the Honeywell HW kit replaced the one that came with my cylinder. There's a tube on the side of the cylinder, so this probe was pushed in and held with a piece of foam. Curiously I can't see that I now have a hot water overshoot protection in place - knowing that this is a staunch requirement for an unvented.... From memory this is a bridge in the live that runs to the boiler main power feed... So presume I just need to hard wire an overshoot thermostat into place?

    As always chaps, any help much appreciated on any of the above

  5. #85
    Automated Home Ninja
    Join Date
    Mar 2017
    Posts
    294

    Default

    Quote Originally Posted by 1animal1 View Post
    Hi all!

    So my system was installed in July. Y plan with unvented cylinder, OT via an IS32 Atag, with a normally closed valve on the water side. Full HR92 set up, no satellite room thermostats.

    All seems to be running well, although I am noticing overshoots on my rads, so thinking I need to maybe reduce the max boiler temp which I haven't yet touched.... Visiting this now as my wife is ********, and starting to think about the rads being very hot with a toddler wandering around in the future.

    Other issues, I had my HW set for 7.30-9am bi-daily. Which seemed to be an issue, as the water wasn't heating at all at a time max demand was being requested from the rest of the house. I've sorted this by increasing the window back to 6am-9am which seems to have resolved.

    And finally, the HW thermostat on the Honeywell HW kit replaced the one that came with my cylinder. There's a tube on the side of the cylinder, so this probe was pushed in and held with a piece of foam. Curiously I can't see that I now have a hot water overshoot protection in place - knowing that this is a staunch requirement for an unvented.... From memory this is a bridge in the live that runs to the boiler main power feed... So presume I just need to hard wire an overshoot thermostat into place?

    As always chaps, any help much appreciated on any of the above
    I'm guessing as you've got a Y plan and a Unvented cylinder you have one 3 Mid position valve and a single 2 port valve on the cylinder. In my experience these never seem to work quite right as whoever has wired them up in the first place has usually got it wrong. As you're experiencing overshoots it's likely because you haven't got Hot Water Priority, so when max flow temperature from the boiler for HW recovery it's being diverted to the rads as well. The easiest way to sort this it make it an S Plan system with two NC 2 port valves, so that when the Hot Water is calling for heat the Heating Zone valve closes (To do this you'd need an Additional BDR91, so one for the boiler, HW, and CH). I can be done using a NO zone valve, which a forum member has done however I prefer it doing it with a Normal 2 Port Valve.

    Yes the existing High Limit stat should be wired in to meet regs. I usually leave the existing dual stat in place and turn it up to max, then set the EvoHome HW set point lower. Doing this means you can never have any issues. No it doesn't run to the main boiler power feed, it should run to the zone valve so when the High Limit Stat kicks in the Zone valve would close and therefore turn the boiler off (If you were using the Microswitch as a S/L).

  6. #86
    Automated Home Jr Member
    Join Date
    Jan 2018
    Posts
    39

    Default

    Thanks MTM!

    First thing, I am actually S plan, sorry... Running as per the Honeywell suggestion, with a valved rad circuit, but with a normally closed valve on the HW to make it more efficient, as per the suggestion from Honeywell's head technical chap.

    The overshoots I've also since noticed are when the hot water was on this morning, it balanced out later on. Will keep an eye on it.

    The limit stat, I have the one it came with so I'll fit that with your suggestion... So to state the obvious, presume it'll be the hot water normally closed valve, effectively cutting power and closing it. Which wires am I bridging?

  7. #87
    Automated Home Ninja
    Join Date
    Mar 2017
    Posts
    294

    Default

    Quote Originally Posted by 1animal1 View Post
    Thanks MTM!

    First thing, I am actually S plan, sorry... Running as per the Honeywell suggestion, with a valved rad circuit, but with a normally closed valve on the HW to make it more efficient, as per the suggestion from Honeywell's head technical chap.

    The overshoots I've also since noticed are when the hot water was on this morning, it balanced out later on. Will keep an eye on it.

    The limit stat, I have the one it came with so I'll fit that with your suggestion... So to state the obvious, presume it'll be the hot water normally closed valve, effectively cutting power and closing it. Which wires am I bridging?
    So you've just got the One Motorised valve and HR92s on all the rads as per the Honeywell Diagram? If you're wanting to prevent overshoots then you need to add in an additional valve on the heating circuit so it would be like a traditional S plan, stopping the flow of water round the CH system when the HW is reheating.

    The Cyl/Limit stat, you need to wire in a series from the HW BDR91. So from B on the BDR91 to Common on your stat, then it's Normally 1 on your cylinder stat to the Brown of the Motorised valve.

    If it's dual aqua stat like you find on most Unvented cylinders (White box with a small black knob on front) you'll find the the link between the High Limit and normal stat has already been made for you inside.

  8. #88
    Automated Home Jr Member
    Join Date
    Jan 2018
    Posts
    39

    Default

    I'll try and take a picture of the limit stat when I can....

    The S plan in the Hwell diagrams shows a valve on the CH circuit and open HW circuit, strictly for opentherm. I also have an additional normally closed valve on the HW circuit to prevent just that... All wired up as per Honeywell's tech chaps suggestion. So the HW is closed until requested and vice versa on the CH

  9. #89
    Automated Home Ninja
    Join Date
    Mar 2017
    Posts
    294

    Default

    Quote Originally Posted by 1animal1 View Post
    I'll try and take a picture of the limit stat when I can....

    The S plan in the Hwell diagrams shows a valve on the CH circuit and open HW circuit, strictly for opentherm. I also have an additional normally closed valve on the HW circuit to prevent just that... All wired up as per Honeywell's tech chaps suggestion. So the HW is closed until requested and vice versa on the CH
    Sorry I'm not sure which diagram you are referring to. None of the diagrams in my EvoHome book show what you are describing? I'm guessing you are referring to a diverter valve rather than a normal valve with what you've described, however that wouldn't be a S plan system then.

  10. #90
    Automated Home Jr Member
    Join Date
    Jan 2018
    Posts
    39

    Default

    If you look at the Opentherm set up for an S plan, optimum set up suggests a single valve on the heating circuit and the hot water branch is entirely open with no valve. I've got a slightly modified version of that with a normally closed valve on the hot water

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •