Page 2 of 2 FirstFirst 12
Results 11 to 18 of 18

Thread: Can evohome drive a boiler with a 3-way mixing valve using the HM80?

  1. #11
    Site Sponsor The EVOHOME Shop's Avatar
    Join Date
    Dec 2014
    Location
    Powys, Mid Wales
    Posts
    479

    Default

    Quote Originally Posted by SensibleHeatUK View Post
    I don't know if Evohomeshop has any experience with this and can confirm if it is any different.
    Sorry only just seen this but sadly I haven't used the HM80 with EVO.

    Quote Originally Posted by sharpener View Post
    Incidentally my experience is that weather compensation is the single most effective measure in reducing energy consumption yet UK heating installers seem woefully ignorant about it. A shame that Danfoss stopped making their Boiler Energy Manager as a retrofit device.
    Weather Compensation is great - I agree it would maximise energy use but certainly not the single most effective measure for reducing energy consumption.

    Having fitted weather compensated systems for some time (both commercial and domestic) and having my own weather compensated Ground Source Heat Pump - WC is something I do widely promote but certainly not a replacement for good controls.

    Retrofitting WC to domestic systems (similar to commercial applications) is not necessarily the most efficient way of doing things. To have a boiler with a flow temperature of 75-82 degrees C to then mix it down to say 40 degrees C is the best a 'bolt on' kit will ever achieve and is in my opinion inefficient. A lot of the 'domestic energy management' systems I have seen really are just 'load compensated' and produce results not dissimilar to what evohome already achieves.

    Much better to have a truly weather compensated domestic boiler (for instance a Worcester Bosch Greenstar CDi with FW100 controls) with zoned heating demand from evohome - this is a great application with the best of both worlds (heating zone control where you need it and accurate boiler flow temperature control) and something I have done many times with excellent results.

  2. #12
    Automated Home Sr Member
    Join Date
    Oct 2014
    Posts
    84

    Default

    True, but if you set the water temperature of the boiler fairly low it'll modulate its output to give the targeted temperature increase required.

  3. #13
    Automated Home Legend top brake's Avatar
    Join Date
    Feb 2015
    Location
    the edge of the cloud
    Posts
    827

    Default

    Quote Originally Posted by Fursty Ferret View Post
    True, but if you set the water temperature of the boiler fairly low it'll modulate its output to give the targeted temperature increase required.
    The boiler temperature will be set during commissioning for example 70 degrees C
    It will modulate down to suit the demand. For example our Vaillant with evohome is currently set to run at max of 70 and is actually at 59 right now, earlier today it was down to 45. Also remember if you want it to heat stored water to 60 it will need to be a bit hotter than that to allow for heat transfer losses.

    If you set it too low it won't condense and will actually be less efficient!
    I work for Resideo, posts are personal and my own views.

  4. #14
    Automated Home Sr Member
    Join Date
    Jan 2015
    Posts
    76

    Default

    Lots of good stuff here!

    Quote Originally Posted by The EVOHOME Shop View Post
    Retrofitting WC to domestic systems (similar to commercial applications) is not necessarily the most efficient way of doing things. To have a boiler with a flow temperature of 75-82 degrees C to then mix it down to say 40 degrees C is the best a 'bolt on' kit will ever achieve and is in my opinion inefficient.
    Agreed. If you do it with a mixing valve the mixing process results in an irrecoverable increase in entropy, much better to have the boiler running at the lower temperature to begin with. This is why combining radiators with underfloor heating does not achieve the energy savings it could if the boiler was in condensing mode all the time. Ideally you would use the return from the radiators as the flow to the UFH.

    Quote Originally Posted by Fursty Ferret View Post
    True, but if you set the water temperature of the boiler fairly low it'll modulate its output to give the targeted temperature increase required.
    Then what happens in a cold snap? The beauty of WC is that once you have set the gradient you don't have to touch the boiler again.

    Quote Originally Posted by top brake View Post
    The boiler temperature will be set during commissioning for example 70 degrees C
    It will modulate down to suit the demand. For example our Vaillant with evohome is currently set to run at max of 70 and is actually at 59 right now, earlier today it was down to 45.
    Is this demand management a feature of the boiler or of the evohome system?

    Quote Originally Posted by top brake View Post
    Also remember if you want it to heat stored water to 60 it will need to be a bit hotter than that to allow for heat transfer losses.
    Does the Vaillant do this automatically? I had to add a relay to cut out the WC when the DHW was calling for heat (though it would have been trivial for Vokera to do this in software).

    Quote Originally Posted by top brake View Post
    If you set it too low it won't condense and will actually be less efficient!
    Eh?

  5. #15
    Automated Home Legend top brake's Avatar
    Join Date
    Feb 2015
    Location
    the edge of the cloud
    Posts
    827

    Default

    Quote Originally Posted by sharpener View Post
    Lots of good stuff here!



    Agreed. If you do it with a mixing valve the mixing process results in an irrecoverable increase in entropy, much better to have the boiler running at the lower temperature to begin with. This is why combining radiators with underfloor heating does not achieve the energy savings it could if the boiler was in condensing mode all the time. Ideally you would use the return from the radiators as the flow to the UFH.



    Then what happens in a cold snap? The beauty of WC is that once you have set the gradient you don't have to touch the boiler again.



    Is this demand management a feature of the boiler or of the evohome system?



    Does the Vaillant do this automatically? I had to add a relay to cut out the WC when the DHW was calling for heat (though it would have been trivial for Vokera to do this in software).



    Eh?
    The TPI works with the boiler management (also Honeywell) to operate the boiler in condensing mode by achieving a return temperature differential of at least 20 deg C and below 55 deg C (dew point)

    I have a really good faq on this i will share
    Edit here it is:

    http://www.honeywelluk.com/documents...0explained.pdf


    Regarding the performance adjustment on a cold day this is where the optimum start helps, it knows to start the heating earlier to achieve temperature
    Last edited by top brake; 8th February 2015 at 11:42 PM.
    I work for Resideo, posts are personal and my own views.

  6. #16
    Automated Home Jr Member
    Join Date
    Dec 2014
    Location
    CH
    Posts
    22

    Default

    Ah ah that is TPI! Very interesting!
    (I initially though you wanted to explain what was a PID, but no, you was right to precise what it is, this is new to me) this document gave me more confidence about Evo energy efficiency but I have the impression Evo is unable to modulate the boiler's power, it seems to be 0 or full power while all recent boilers have different power available to improve efficiency in condensing mode.

    Many thanks to all the contributor to this post.

    By the way, you convinced me to abandon my mixing valve, and I'm looking to find an OpenTherm boiler. I started a new post to discuss the OT boiler/Evo good combinations and possibles issues:
    http://www.automatedhome.co.uk/vbull...ight=opentherm
    Last edited by courcirc8; 2nd April 2015 at 08:24 AM.

  7. #17
    Automated Home Jr Member
    Join Date
    Dec 2014
    Location
    CH
    Posts
    22

    Default

    The boiler I'm currently targeting is the OERTLI OEnoviaFioul OVCR (18 or 24) with hot water tank 100HL which is apparently the same boiler as the Remeha Calora Tower Oil & Tank BS 100 HL.
    This boiler has two output circuits:
    -one direct circuit.
    -the second one through a 3-way mixing valve.
    Can you confirm that is is recommended to branch my installation on the direct circuit, in order to work in TPI mode?
    Many thanks

  8. #18
    Automated Home Jr Member
    Join Date
    Dec 2014
    Location
    CH
    Posts
    22

    Default

    Quote Originally Posted by The EVOHOME Shop View Post
    Much better to have a truly weather compensated domestic boiler (for instance a Worcester Bosch Greenstar CDi with FW100 controls) with zoned heating demand from evohome - this is a great application with the best of both worlds (heating zone control where you need it and accurate boiler flow temperature control) and something I have done many times with excellent results.
    I tried to let my weather regulation work on my current boiler (3 way mixing valve) but without communication with Evo It gives bad results: output temp are too low and zone regulation doesn't work, and when I change the regulation coefficient, output temp are at max...

Tags for this Thread

Posting Permissions

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