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Thread: Evohome with electric underfloor.

  1. #1
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    Post Evohome with electric underfloor.

    Another new self-install Evohome user here. Having been inspired by the PC Pro review I completed the Honeywell on-line training course and purchased a system.

    My system is S-Plan with HTG and DHW 2-way zone valves, gas boiler and pump. I have wired exactly as per S-Plan diagram (Figure 9) in the installation guide.

    I have 14 radiators in 10 zones controlled by HR92s, the living room has a TR87RF thermostat.

    The system is set up on the bench for testing and works as it should.

    I am wanting to add an additional zone to control a self-regulating electric underfloor heating mat. This is switched by a low voltage contact closure.

    My plan was to add a DTS92 thermostat and BDR91 relay box. I have added this as an additional zone, binding the BDR91 as a ‘zone valve’. However, when this zone calls for heat both the HTG BDR91 and additional zone BDR91 switch on together. The HTG BDR91 switches on its own when a HR92 calls for heat.

    Any help as to where I have gone wrong in setting this up would be appreciated.

  2. #2

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    This I am afraid will be the case. The system was not originally programmed with E-UFH in mind. As a normal zone valve would need 'heat'. evohome doesn't know its electric.

    Typically in my home, my kitchen (with the E-UFH) is not on without one or another radiator on - so this doesn't bother me. But this is a limitation I am afraid (for now)
    getconnected.honeywell.com | I work for Honeywell. Any posts I make are purely to help if I can. Any personal views expressed are my own

  3. #3
    Automated Home Legend paulockenden's Avatar
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    It was perhaps my fault in the PC Pro article as I mentioned E-UFH there. The system is fine if ALL of your heat is UFH (i.e. no boiler). That's what I was alluding to in the article. But like Rameses says, in most homes UFH will be on with radiators at the same time.

    Apologies if my article was confusing in this respect. It's difficult to cram everything that is Evohome into 2800 words!

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    Thank you Rameses for your reply at least I know I am not getting the set-up wrong, lets hope Honeywell will fix this in the future.

    And Paul no need for apologies, as I said your articles inspired me into getting what still is a excellent system.

    Tony.

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    It is a shame that there is no electric underfloor option to add to EvoHome. I have this in my master bathroom (as I'm sure many have) and I can't control it in any fashion from EvoHome at all. Even if it could just be a timed zone with no boiler demand that would be useful.

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    Automated Home Legend paulockenden's Avatar
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    Just a thought - if you don't have stored hot water I wonder whether it would be possible to utilise that part of the system for one zone of UFH? I can't see why it wouldn't work...

    P.

  7. #7
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    Evohome so nearly has the ability to control electric UFH, it is only the additional command to the S plan zone vale that stops it. Surely it can't be too difficult for Honeywell to change this.

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    Quote Originally Posted by paulockenden View Post
    Just a thought - if you don't have stored hot water I wonder whether it would be possible to utilise that part of the system for one zone of UFH? I can't see why it wouldn't work...

    P.
    Because you can't just use floor temperature alone... What will control the air temperature?

    So you are the reason I have been telling so many people lately electric UFH and evohome is a no no!

  9. #9
    Automated Home Legend paulockenden's Avatar
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    Probably. Especially as I gave you a plug! What I wrote was "If you have underfloor or electric heating there are also options available to you, but as I don’t have either of those I can’t really cover them in a ‘Real World’ manner.", so I don't feel TOO guilty! I was mainly thinking that Evohome would be fine in a situation where it was all UFH or other electric sources, and no boiler.

    As to temp, wouldn't it work with a DT92E doing the temp sensing, and a BDR91 controlling the E-UFH. Like others have said above, this isn't properly supported as a zone in a hydronic system, but I can't see why the HW side couldn't be used if there's no stored hot water. Configure the system as S-Plan. So the heating BDR91 controls the boiler and the 'hot water' one controls the UFH, without the boiler firing. Why wouldn't that work? I know it's a hack, but...

    I guess the only major problem is that you can only set a single temp, so you'd have to use something like IFTTT to create a schedule.

  10. #10
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    Quote Originally Posted by paulockenden View Post
    Probably. Especially as I gave you a plug! What I wrote was "If you have underfloor or electric heating there are also options available to you, but as I don’t have either of those I can’t really cover them in a ‘Real World’ manner.", so I don't feel TOO guilty! I was mainly thinking that Evohome would be fine in a situation where it was all UFH or other electric sources, and no boiler.

    As to temp, wouldn't it work with a DT92E doing the temp sensing, and a BDR91 controlling the E-UFH. Like others have said above, this isn't properly supported as a zone in a hydronic system, but I can't see why the HW side couldn't be used if there's no stored hot water. Configure the system as S-Plan. So the heating BDR91 controls the boiler and the 'hot water' one controls the UFH, without the boiler firing. Why wouldn't that work? I know it's a hack, but...

    I guess the only major problem is that you can only set a single temp, so you'd have to use something like IFTTT to create a schedule.
    As per your article, sort of Paul. I do appreciate the plug BTW! Our business unit is all electric and evohome controls this completely. We also have electric UFH and it also controls this with the addition of another manufacturers floor probe in series with the HC60NG wireless relay boxes we have.

    But electric anything plus evohome on a wet system with a boiler relay or HTG valve actuator is a big no. I can see some failed boilers where they have been cycling their heads off (on electric UFH demand) around a bypass circuit for 8 hours a day and it is just something I certainly wouldn't recommend or want on my conscience.

    I am unsure how you can combine the hot water CS92 and a DTS92 to control electric UFH? The DTS92 would demand the boiler relay/HTG valve actuator as would the CS92, so the boiler would cycle.

    On a different topic, I do need educating how I can do more with PC's and evohome! I am sure you could do an article on this...

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