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Thread: 13th Zone?!

  1. #1
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    Default 13th Zone?!

    The Evohome website says "if you need more than 12 zones contact us". I've seen reference on the forum to having two controller panels set up in parallel on the heating relay since but that is two separate systems as far as I can see.

    I have the following house to which I've already started fitting EvoHome in a few rooms:

    Zones:
    1. Kitchen
    2. Family Room
    3. Living Room
    4. Garden Room
    5. Dining Room
    6. Office
    7. Bedroom+Ensuite
    8. Spare Room
    9. TV Room
    10. Library
    11. Bathroom
    12. Loft
    13. **communal spaces, utility room**

    I'm aware of multi-room zones and this is already used for bedroom+ensuite - and would be for zone 13 if I could have a zone 13. I can leave these all on the old TRVs to 'steal' heat but this strikes me as not optimal?

    So my question is - is the system actually limited to 12 zones or can an expert installer do anything clever? If you had two controller units can they be bridged? Can one hack the system? I'm already going to have ~ 20 radiators if the zone 13 radiators are included - if there's a way to avoid splashing out on another controller I'd love to hear from an expert user or Honeywell nerd

  2. #2
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    You are limited to 12 zones.

    So your choices are:

    1) Spread the system over two controllers (more complicated, inconvenient and not really worth it for 13 zones)
    2) Leave some radiators on manual TRV's
    3) Make more use of multi-room zones. For example if you have any open plan areas that are currently divided into separate zones there is not much point doing that - make them one zone, or if they are large or odd shaped (like an open plan living room/kitchen combo) make it a multi-room zone even though it is one area so the individual radiators measure their own part of the room, which will give a more even temperature distribution than using one measurement location.

    Up to you!

  3. #3
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    I might be able to squeeze 1+2 onto a multi-room zone since IIRC I can set different temperatures for different radiators in this scenario(?)... the rooms are joined by a small arch but it's not optimal because we tend to go in there only to prepare food so it can be cold. Perhaps the way to go - I can then have a "communal area zone". I don't really want all the communal areas automatically getting heat just because I have the bedroom keeping warm overnight for instance so having all that area unzoned appears a problem to me.

    It seems almost certainly the case the 12 zone limit is artificial in the software design. When it said "contact HoneyWell if you need more" I thought the case might be they'd seize the opportunity to make more money by sending out an 'engineer' to unlock more zones (enter a special password to turn it on!)

    As far as we know even if you get multiple controllers, they are totally independent then? They don't have a bridging mode so you'd have two locations in your account/app to manage? I know Honeywell developers are active here, it'd be really interesting to speak to one of them about it - could they ever expand this in future?

    Also the homebrew community - I wonder if they have any tricks here? Whether the Web API offers more control or only let's me access zones not TRVs?

    EvoHome is the best system for large homes I'm aware of so it seems a bit odd it stops working just the point your home really starts getting above average - we are fundamentally just a 4/5 bderoom property so there are many people in far larger houses. What do they do?

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    Quote Originally Posted by MrBoy View Post
    I might be able to squeeze 1+2 onto a multi-room zone since IIRC I can set different temperatures for different radiators in this scenario(?)...
    No, when you have a multi-room zone, the schedule is the same for all radiators in the zone even if they are different rooms. You can manually override individual HR92's in a multi-room zone temporarily, however they will resume the shared schedule at the next set point change.
    It seems almost certainly the case the 12 zone limit is artificial in the software design. When it said "contact HoneyWell if you need more" I thought the case might be they'd seize the opportunity to make more money by sending out an 'engineer' to unlock more zones (enter a special password to turn it on!)
    It's almost certainly an "artificial" software limit, my guess is it is probably related to the user interface design and layout - you can get 6 zones per screen, so 12 zones = 2 screens. If they were to go beyond that 18 zones would make sense as that would be 3 screens.

    A similar thing seems to apply to the limit of no more than 6 set point changes per day in a zone - the 6 set points just fit across the screen neatly in the schedule edit page and I suspect that's why it's 6 and not some other number! (I bump into the 6 set points limit quite often believe it or not, and have had to somewhat simplify my schedule in a couple of rooms from what I'd prefer)

    I suspect if you were to "contact honeywell if you need more" they would advise you on the merits of either simplifying with multi-room zones, or suggest you buy a second controller!
    As far as we know even if you get multiple controllers, they are totally independent then? They don't have a bridging mode so you'd have two locations in your account/app to manage? I know Honeywell developers are active here, it'd be really interesting to speak to one of them about it - could they ever expand this in future?
    From what I've seen if you have two controllers then you just have two different "locations" to deal with in the phone app/website, and there is no synchronization between the two controllers as such - so for example you would have to set away mode on both of them if you want to be away, and given that they are probably in different parts of the house (some people use a two controller config as one doesn't have the wireless reach for a large house) that is a bit inelegant.

    You then have the issue of two different controllers both trying to do TPI on the same BDR91 (or two BDR91's wired in parallel) and that seems sub optimal to me, although I'm sure it must work. (Not sure how you'd do it with OpenTherm though!)
    Also the homebrew community - I wonder if they have any tricks here? Whether the Web API offers more control or only let's me access zones not TRVs?
    I doubt that it's possible to sneak more zones in using the web interface API. I've not heard anything along those lines and the API only lets you access zones not individual TRV's.
    EvoHome is the best system for large homes I'm aware of so it seems a bit odd it stops working just the point your home really starts getting above average - we are fundamentally just a 4/5 bderoom property so there are many people in far larger houses. What do they do?
    They probably have two controllers, and put up with the inconvenience of that, or use some other system entirely.

    Bumping the number of zones up to 18 would certainly extend the reach of Evohome to larger houses on paper, but I have to wonder if that has not been done to avoid trampling on a higher end product (does Honeywell still do anything equivalent to Hometronic ?) or whether they have just decided that a house that needs more than 12 zones is probably physically too big to get good reliable wireless coverage from the controller to all points of the house, and thus don't try to encourage it by allowing it to support more zones than it feasibly could from a wireless range perspective ?

    Even with 12 zones there are houses where a single controller can't reach all the zones, especially expansive, stretched out single level houses.
    Last edited by DBMandrake; 11th January 2018 at 03:52 PM.

  5. #5
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    Quote Originally Posted by DBMandrake View Post
    No, when you have a multi-room zone, the schedule is the same for all radiators in the zone even if they are different rooms. You can manually override individual HR92's in a multi-room zone temporarily, however they will resume the shared schedule at the next set point change.
    I know in a multi-room zone you have to have the same schedule (else it would just be 2 zones) but can the different areas have different temperatures set? Or is the only difference between a multi-TRV zone and a multi-room zone that in the latter case, all TRVs act as thermostats rather than one being the master and the others just 'dumb' actuators slaved to it?

  6. #6
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    Quote Originally Posted by MrBoy View Post
    I know in a multi-room zone you have to have the same schedule (else it would just be 2 zones) but can the different areas have different temperatures set? Or is the only difference between a multi-TRV zone and a multi-room zone that in the latter case, all TRVs act as thermostats rather than one being the master and the others just 'dumb' actuators slaved to it?
    Here's how the two work in detail.

    Single room zone: (the default for a new zone)

    One temperature sensor for the entire zone. This is the first device you bind to the zone after creating it, although you can easily change it later by selecting a new device as the "sensor".

    The sensor can be the evotouch's built in sensor, one of the HR92's in the zone, or a wall stat like a DTS92.

    The temperature reading from the sensor, whatever it is, is sent to the Evotouch periodically (unless the Evotouch is the sensor, then it already has the reading from its built in sensor) and then periodically re-sent to all HR92's in the zone by the controller. They all use this same temperature reading to adjust their own individual radiators. They then all send back their own individual heat demands to the Evotouch (based on their valve position) and this is used by the Evotouch to decide how much to fire the boiler. All HR92's in the zone will display the same temperature reading from the originating sensor if they are in room temperature display mode, not their from their own sensor.

    Any HR92 who is not the sensor for the zone it belongs to will ignore its own built in temperature sensor except for the open window function, which still seems to use a sudden drop in temperature measured at the HR92 to detect a window has been opened. As far as I can see a remote sensor does not do open window detection. So in my living room where I use a DTS92, the temperature measured at the DTS92 is what controls the room temperature, but the temperature measured at the HR92 (not displayed anywhere) still controls activation of the open window detection.

    Scheduled set point changes or changes made via the controller/phone app are sent to all HR92's in the zone at the same time, with up to a 4 minute delay.

    If you manually override one HR92 in the zone using the wheel on the top that HR92 changes set point immediately, the set point is sent to the controller, updates the set point displayed on the controller with a pocket watch icon and within 4 minutes the other HR92's in the zone will follow suit and change their own set points to match. So from this perspective there can be only one set point in the zone, apart from that few minute delay until other HR92's update. So it doesn't matter which radiator you adjust in the room, they will all be the same after a few minutes.

    The temperature displayed on the controller for the zone is that measured at the nominated sensor for the zone.

    Multi-room zones differ in the following ways:

    All HR92's in the zone work purely off their own individual built in temperature sensors and adjust their own radiator accordingly and independently. If they are in room temperature display mode they all show their own built in sensors measurement.

    Whichever HR92 is bound first becomes the "nominated" sensor for temperature display on the controller - so if you have three rooms in a multi-room zone, that "nominated" HR92's temperature reading is shown on the controller and the other two HR92's temperature readings are not shown anywhere, except on the individual HR92 displays if they are set to room temperature display mode.

    It's unclear whether you could bind a wall thermostat like a DTS92 in a multi-room zone - if you can (I haven't tried it) it would probably only affect the displayed temperature on the controller but not affect the control of the radiators in any way! (So it doesn't make sense to do it)

    If you make a manual override on any HR92 in a multi-room zone it is not reflected on the display of the controller, nor does this change get propagated to other HR92's in the same zone. This gives you the ability to manually override an individual radiator in a multi-room zone from the HR92 without it affecting other radiators in the zone, which you cannot do in a single room zone. This makes sense because for example if you had a zone consisting of two bedrooms you wouldn't want someone manually adjusting the radiator in their room to affect the other bedroom even though the bedrooms share the same schedule!

    Hope that clears everything up.
    Last edited by DBMandrake; 11th January 2018 at 04:27 PM.

  7. #7
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    Very instructive, thankyou.

  8. #8
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    There's a big-boys product, similar to Evohome but which has more zones. Can’t remember the name but the heating professionals on the forum here sometimes complain that they aren’t allowed to sell/install it.

  9. #9
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    That would be Smile.

  10. #10
    Automated Home Legend paulockenden's Avatar
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    That's the one. The controller is 1.5k. And the app.... I think it was designed by the same team that did the current TCC app.


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