Page 1 of 2 12 LastLast
Results 1 to 10 of 15

Thread: Help!! Need advice re switching Evomhome from BDR91 to OpenTherm boiler control

  1. #1
    Automated Home Lurker
    Join Date
    Jan 2018
    Posts
    4

    Default Help!! Need advice re switching Evomhome from BDR91 to OpenTherm boiler control

    Hi all,

    First off a disclaimer! I am not a heating engineer and have relatively limited knowledge in this area so apologies if I misrepresent something... I'll try to be as acurate as possible.

    My aim is to take my fully working system from being driven by BDR91s to the RA8810 OpenTherm module to benefit from the intelligence that this brings.

    Ok, so first things first... the kit

    Ideal Vogue Gen 2 S26 boiler
    EvoHome WiFi controller
    Evohome UFH Controller (No Actuators, the EvoHome pad acts as the temp sensor)
    EvoHome CS92 Hot Water kit (Strap-on sensor)
    EvoHome BDR91 (CH + DHW)
    EvoHome RA8810 (Fitted and ready to go but currently disconnected)
    EvoHome HR92s on pretty much all radiators (except bathroom towel rails and one radiator)
    1 x 2 port valve connecting the UFH into the main flow & return
    1 x 3 port valve for water flow to either CH / DHW / Both

    So as I indicated above, the system works fine today. It was commissioned around 9 months ago and at that time everything above (except the 3 port valve) was bought together as this was a new install. The engineer was happy enough to do the work but was completely stumped by the EvoHome system generally and even more so by the OT module... for a time it was connected and flashing green, but I gather so was the switched live for the BDR91s. After a while and a callout to fix a different problem the OT was disconnected as the guy just couldnt figure it out.

    Fast forward and I have recently had a differnent engineer visit (a honeywell connected specialist) with one more to come next week with the express wish to sort this out so that I can have the OT module doing what it is meant to.

    The engineer provided a quote for the remedial works which includes the following:

    - Fitting an automatic bypass
    - Removing the 2 port valve for the UFH and fitting Actuators
    - Swapping the 3 port valve for a 2 port valve for just the hot water (presumably the CH flow is then constant ?)
    - A complete rewire and re-commision of the system

    I am happy to go ahead with this work if it is needed but from my reading I am really unsure! I can see the benefit of going to an S-Plan system over the current Y and I believe once you get to the 24Kw level you should really have a bypass, but his proposal doesn't seem to be that, its more of an alternative S-plan..ish but I am not sure.

    From reading this forum and others I think very simplistically all that needs to happen is that the switched live going from the wiring center to the boiler gets removed and the the OT connections added... this way the BDRs would still work the valves but not trigger the boiler, leaving that to the OT module.

    I am looking for any and all advice on the best way to achieve the end goal of the OT module....but also to correct any issues with the system that need to be addressed.

    My gut is leaning towards changing to a proper S-plan and getting the bypass fitted but happy to listen to others views.

    All advice gratefully received.

    Many thanks

    Rob

  2. #2
    Automated Home Ninja Dan_Robinson's Avatar
    Join Date
    Jun 2012
    Posts
    347

    Default

    Do what the engineer has told you needs doing.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

  3. #3
    Automated Home Lurker
    Join Date
    Jan 2018
    Posts
    4

    Default

    Hi Dan, thanks for youre quick response.

    I will work probably end up doing what the guy says but my aim from the post was to understand as much as possible about my situation and the art of the possible based on others experiences.

    So if you have any thoughts on the validity of my thinking re the switched live or any of the suggestions made by the engineer then Iíd love to hear them so I can build as complete a picture as possible.

    After all if I can sort the system out without making all or some of the changes (and incurring the significant extra cost) thatís all for the better.

    Thanks again

    Rob

  4. #4
    Automated Home Ninja Dan_Robinson's Avatar
    Join Date
    Jun 2012
    Posts
    347

    Default

    Well, the UFH zone valve is not appropriate, especially if you are moving to a compensated flow temperature. It will jam open.

    The HR92's perform the same role as a zone valve, so the valve on that circuit is surplus to requirement and one more thing to go wrong - again especially so when you are running compensated flow systems.

    In actual fact we/he should be calling it a "de-wire" of the system as Evohome tends to end up with fewer wires and a less cluttered wiring centre.


    I am of course, assuming it is going to be wired correctly.


    What the connected socialist is suggesting is the preferred way of wiring/controlling the system and is exactly how I would do it (possibly sans by pass circuit, however he is correct to fit one). I am a connected specialist too BTW.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

  5. #5
    Automated Home Ninja
    Join Date
    Mar 2017
    Posts
    440

    Default

    Sounds about right to me also, however I would keep the Motorised Valve on the UFH manifold - i'm sure Dan will probably argue with me on this one

    However I have to agree on the bypass, you don't need it if you have rad's and towel rails with no TRVs on.

    TBH i'm surprised your system has even been working correctly, you shouldn't of had a 3 port valve with UFH to start with.

  6. #6
    Automated Home Ninja Dan_Robinson's Avatar
    Join Date
    Jun 2012
    Posts
    347

    Default

    Quote Originally Posted by mtmcgavock View Post
    Sounds about right to me also, however I would keep the Motorised Valve on the UFH manifold - i'm sure Dan will probably argue with me on this one

    Of course I will....

    Capture.JPG
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

  7. #7
    Automated Home Ninja
    Join Date
    Mar 2017
    Posts
    440

    Default

    Quote Originally Posted by Dan_Robinson View Post
    Of course I will....

    Capture.JPG
    But why is it going to be open all the time? You have a compensated flow temperature however your UFH loops won't run 24/7......

  8. #8
    Automated Home Ninja Dan_Robinson's Avatar
    Join Date
    Jun 2012
    Posts
    347

    Default

    They could in the middle of winter. I have replaced dozens upon dozens of synchron based two ports over the years. They are simply not designed for the job of UFH control.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

  9. #9
    Automated Home Ninja
    Join Date
    Mar 2017
    Posts
    440

    Default

    Quote Originally Posted by Dan_Robinson View Post
    They could in the middle of winter. I have replaced dozens upon dozens of synchron based two ports over the years. They are simply not designed for the job of UFH control.
    Yes we do too, but funnily enough i've not replaced any on the UFH systems we've done (Although that's a very small sample size). They simply don't make them like they used to, even on a standard system i'm replacing some that are about 5 years old. I took one out yesterday that was still working and fitted the 1980's however that was made in Canada....

  10. #10
    Automated Home Ninja Dan_Robinson's Avatar
    Join Date
    Jun 2012
    Posts
    347

    Default

    I have noticed more are failing (from all brands) on all fronts over recent years. Another reason to do away with them when they aren't necessary.

    Although saying that, the failures seems to be - gears wearing out or losing teeth on cylinders and rad circuits and cylinders. And UFH seizing solid in the on position with end switches making demand.

    The thermoelectric actuators seem to be as if not more reliable and are designed for the job of staying on for days on end.

    My standard installation practice now is a 3 port valve plumbed backwards for hot water priority. Makes it all nice and simple and covers G3 safety requirements too.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

Posting Permissions

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