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Thread: New Evohome install - questions on local override and zone binding

  1. #1
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    Default New Evohome install - questions on local override and zone binding

    Hi All,

    I've been researching and reading about Evohome since the Colour model was first announced at the end of 2013.

    In March I bought a single HR92UK to test compatibility with my radiator valves and get a sense of how effective the radiator controller was at regulating the room temperature compared to a manual TRV, intending to buy the main controller and more HR92UK's soon after. I was very pleased with how well it performed in the living room (even unbound as a standalone device) but the funds to buy more of the system didn't appear until now... fortuitously as it turned out, as the Wi-fi model came out in the intervening time

    Earlier this week I installed a new Evohome Wi-fi consisting of the connected pack (controller+BDR91) and wall mount to add to the existing HR92UK in the living room.

    The controller is mounted in the hallway adjacent to the living room on the wall mount in the location where the old wall stat was. At the moment there is no radiator controller in the hallway.

    The boiler is a 20 year old "conventional" boiler with just on/off control via the BDR91 (which replaces both the old external timer and wall stat) and no zone valves. Hot water is stored but is a thermosyphon system, not directly pumped.

    By and large the system is working excellently however there are three questions I have:

    1) The original Evohome colour did not support displaying an HR92UK manual override on the main controller screen, however according to this post by Rameses (and others) the new Wi-fi model does support showing the HR92UK's local override.

    This is not working for me. I have tried various ways of binding, guided and manual setup etc, and for me I get the same behaviour that would be expected from the older non-wifi model - eg the Evotouch controller can send a setpoint update to the HR92UK, the temperature measured at the HR92UK is displayed on the controller, but local temperature overrides made on the HR92UK are never propogated to the controller screen even after waiting a considerable time.

    Have I missed something in the binding process ? Is it possible that an HR92UK bought in March does not have a firmware that is new enough to support this functionality ? (If so I have not seen any mention of newer HR92UK's being required for this to work)

    2) I had perhaps naively assumed that I would be able to use the internal temperature sensor in the Evotouch controller in the hallway zone without a radiator valve (temporarily) and also use a second zone with an HR92UK at the same time - apparently not, without cheating anyway...!

    In single Zone mode the Evotouch controller internal sensor will happily control the boiler relay to control that zone with TPI, however attempting to add another zone forces this zone to be removed, and if there are multiple zones present you are forced to bind every zone to an actuator of some kind. There is no option for one zone to only contribute to the boiler relay control but without having it's own actuator.

    Since many people are upgrading from traditional single thermostat bypass radiator systems this seems to be a glaring oversight.

    Trying to fool it by choosing radiator controller then just pressing the tick without actually binding anything does not work - the zone is present and works in every other way except it will not fire the boiler...

    Looking through the list of actuators for a workaround I realised the Zone Valve can also use a BDR91, and being aware that you can bind multiple devices to a BDR91 I decided to try a hack - I purposely double bound two functions to the BDR91 boiler relay - both the boiler relay function, and as a Zone Valve for the zone for the hallway. Much to my surprise it seems to work fine.

    Either zone demanding heat will turn on the boiler, either zone on it's own demanding a small amount of heat seems to cycle the boiler on and off in accordance with TPI. In short it seems to work just as I hoped but I have a couple of concerns about this unusual binding:

    a) Does the zone valve output for a zone also support TPI like the boiler relay output does ? It seems to, but I'm not completely sure. If it does, does it share the same cycle rate configuration (6 per hour etc) as the boiler relay output ? Does it support the same minimum on time setting ? (I have it set to the default 1 minute as the boiler is instant fire)

    b) What happens to the effective TPI percentage when the BDR91 is being sent a demand both for the boiler relay function and the zone valve function ? Does it just add them together ?

    For example say the living room with HR92UK required a demand of 50% and the hallway with "zone valve" required 30% - would the Evotouch controller add the two demands together and send a demand of 80% to the "boiler relay", but also send a demand of 30% to the "zone valve", thus causing the BDR91 to add the two together to 110% and therefore stay on continuously ?

    Another way of looking at this is does this double binding mean that the hallway zone effectively gets its demand figure doubled as far as the actual boiler on-time is concerned ? If so this is certainly not ideal.

    Is there a better way to do this than fooling it by binding the zone as a zone valve ? Nothing else I've tried works so I guess I don't have much choice until I can afford an HR92UK for the hallway radiator, however other rooms are likely to get priority first.

    3) The reliability of the online service for remote control via phone apps seems to be pretty poor so far. We have a 152Mb connection with Virgin media that performs excellently, the controller is only about 4 metres from the base station with direct line of sight through the living room door. The controller itself reports an excellent signal received and is not reporting losing the wifi connection.

    In the 4 days that I've had the system I've had no less than 10 emails from Honeywell telling me "Alert: Failed System Change" in response to trying to update something like a set point from my phone. In most cases at the time I was in the house and know for a fact that the internet connection was working, and invariably trying to perform the same action a second time a few seconds or a minute or so later succeeds.

    This is quite annoying because the UI of the App indicates that a change was successful, I quit the app, a couple of minutes later I receive the email alert (I have it set to immediate) and go back into the app - sure enough, the change has reverted back.

    Is this typical of the performance of the Honeywell servers ? So far I have not had any communication lost alerts except when I have rebooted my wifi router so it doesn't seem to be a loss of communication as such, but rather changes being pushed to the controller are not always getting through.
    Last edited by DBMandrake; 6th December 2015 at 01:49 AM.

  2. #2
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    Quote Originally Posted by DBMandrake View Post
    Hi All,

    I had perhaps naively assumed that I would be able to use the internal temperature sensor in the Evotouch controller in the hallway zone without a radiator valve (temporarily) and also use a second zone with an HR92UK at the same time - apparently not, without cheating anyway...!
    My understanding is that it is possible to use the controller without any HR92s fitted. I have 12 zones and my hallway/stairs is configured such that the Evohome controller is the temperature sensor rather than any of the 3 HR92s in this particular zone. The other 11 zones are controlled via HR92s.

  3. #3
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    Not the same situation - you have three HR92UK's in your hallway zone bound as actuators even though they are not measuring the temperature - I have none.

    If you try to configure a zone which has no actuators using the built in temperature sensor it will not call for heat from the boiler - unless you have configured a single zone system. With multiple zones it won't let you do this.

  4. #4
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    Quote Originally Posted by DBMandrake View Post
    Hi All,
    Looking through the list of actuators for a workaround I realised the Zone Valve can also use a BDR91, and being aware that you can bind multiple devices to a BDR91 I decided to try a hack - I purposely double bound two functions to the BDR91 boiler relay - both the boiler relay function, and as a Zone Valve for the zone for the hallway. Much to my surprise it seems to work fine.
    Sorry to dredge this up from years ago - I wondered if you still used this double binding and/or if you had any problems with it?

    I'm tempted to do the same thing, so that I can fire up towel radiators on demand in summer (which I'd rather not put HR92s on). I've been looking about for anyone doing something similar, and this is the only example I've found.

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