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Thread: Z-Wave timer/roomstat?

  1. #1
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    Question Z-Wave timer/roomstat?

    Hi,

    Is there a Z-Wave room stat that also contains 7 day timer logic? I must admit I cannot find any - only room stats that expect (I assume) to be controlled by a central programmer.

    I'd like a system where each room is self contained, with the only weak point being the boiler relay - and where the room user has easy and direct access to adjust their programming and temperature.

    Cheers,

    Tim

  2. #2
    Automated Home Sr Member Quinten's Avatar
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    How about a Heatmiser PRT-TS Wifi? I've got 2 of those and using a plug-in on my Vera Z-Wave controller can control them locally, or using the Z-Wave controller...

  3. #3
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    Thanks - yeah - I did look at Heatmiser.

    But I decided the wiring would be excessive and I'd need to drop wires to a thermal wax actuator at the radiator, or have a motorised zone valve in the feed pipe.

    Then I'd also have to "OR" all the outputs to drive the boiler demand.

    My "ideal" system so far is actually the Conrad FHT - but the simplex comms bothers me (it is rumoured to be unreliable when you get too many, say >8-10 controllers babbling on the air.

    Z Wave looked interesting, having some interoperability and following a standard, yet being simpler (unlike zigbee) but having zigbee's mesh routing (subject to device support).

    I am happy with the Stella-Z valve (the Danfoss is rumoured to be unreliable, seem a report where the owner had to pull the batteries out every few days to get it to talk to the network).

    I'm happy with the choices for boiler control.

    What I would like to find is a Z-Wave version of the FHT80B which is a room timer stat.

    That leaves the system composed of relatively standalone components (save the boiler relay and I can have a spare) - but also with the option to remote control everything.

    I am a *great believer* in fancy systems being able to degrade gracefully in the even of faults. I'd even keep a boiler timer ready and wired and a few TRV heads in case the whole system failed

  4. #4
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    How many Stella-Zs do you think you'll have? (Z-Wave isn't a great protocol for running large numbers of battery powered devices)

    And how do you expect the Stella-Zs to fit in with your independent room thermostats?

    By the sounds of it you're asking for each zone to have its own controller that triggers both the Stella-Z and the Boiler Relay. Thats a degree of redundancy I just don't think you're going to find.

    Horstmann do a 7 day Z-Wave programmer, but it only speaks to the Boiler Relay so if you're looking at radiator stats too that isn't going to work.

  5. #5
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    Good questions to which I have answers

    11-12 Stella-Zs

    In most cases, one per room stat, in 2 cases, 2 StellaZs on a single room stat.

    2 StellaZ's will be paired with a 2nd "boiler relay" that actually starts the low temperature mixing circuit (underfloor heating, needs <=40C rather than 50-60C) and I will use simple relay logic to cause a boiler demand from this.

    The rest will be bound with the primary boiler demand relay.

    That's the base system - there will be some central point of control but if that fails, the system should basically operate.

    There are likely to be other ZWave devices (meter readers, odd controls for lighting outside).



    > "By the sounds of it you're asking for each zone to have its own controller that triggers both the Stella-Z and the Boiler Relay. Thats a degree of redundancy I just don't think you're going to find."

    Yes - that sums it up Exactly how you might deploy the Conrad FHT. Well, I can use the FHT if I am careful to test the system is not missing too many messages, but as I said, ZWave looked cute.

  6. #6
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    Right well 11-12 Stella-Zs is possibly pushing it, especially if you're planning to have (battery) thermostats in lots of the rooms and are looking for a responsive system. There is a thread on the Indigo forums about Stella-Zs and the problems of the Z-Wave protocol when you have lots of devices waking up and needing a quick response from the controller. The people behind Indigo have modified the software to avoid it crashing, but with 12 rad valves and half a dozen thermostats I think you're pushing the limits of the protocol from what I've read (certainly enough so such that I went cool on the idea of the system as its a lot of money to discover it isn't reliable).

    Stella-Zs are slave only devices so they can't speak to the boiler relays directly. I'm not sure whether they can take "associations" such that you could have them directly controlled by a thermostat as well as a central controller (and as per my earlier post the only 7 day Z-Wave thermostat I'm aware of in the UK won't pair with anything except its own boiler relay). You might have luck with the Horstmann dial thermostat to give local (but not programmed from the device) control to some extent assuming (i) the Stella-Z can be associated with the thermostat; and (ii) the thermostat gives the right commands to actually be of any use to the Stella-Z. On the latter point it definitely can't send the current set point to the Stella-Z, so the best you could hope for (though it should work) is to set the Stella-Z to 25 degrees with the main controller and then have the thermostat flick it between that and frost protection modes (6 degrees) depending on whether the thermostat thought the room needed heat.

    Whether you can bind half a dozen thermostats with a central controller and also with a single boiler relay (which in turn is bound to the central controller as well) is a similarly questionnable scenario but more likely to work as it really just turns on whether the boiler relay accepts associations and if so how many.

    All in I'm highly doubtful whether you can get anything close to what you're looking for in terms of redundancy if the controller goes down. I also think you're pushing Z-Wave altogether which is why I've abandoned (after a lot of research) the idea of doing what you're looking for relying on central control as well.

  7. #7
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    Thank you for that.

    I did not know the StellaZ's were simplex - I assumed they could at least manage an "ACK" and maybe return status (eg battery level and valve position).

    As I understand it, in the Conrad FHT system, the room timer/stats are bound with one or more FS20 radiator valves and with upto one boiler relay (which may be bound with upto 10 room stats).

    The rad valves are simplex with the message frame repeated 3 times.

    The boiler relay is also a passive simplex device that listens for "valve open" type messages from it's associated stats.

    So the only signal is each room stat sending 3 messages every couple of minutes. I do not think the system has any collision avoidance/retry logic (which is tricky with radio systems, but possible to a limited extent).

    The room stats are duplex so may be interrogated and remote commanded from a central controller.

    I assumed the ZWave devices were similar, but with duplex comms for more reliability and a more standardised protocol, but I could be wrong....

  8. #8
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    If you're using a proper controller then yes you get acknowledgements, battery, set point and temperature - I was just meaning if you try to have them speak straight to a thermostat you won't get that.

    The problem is actually because of the collision detection etc. To save battery they only wake up briefly. The problem is then if you get two waking up at the same time one of them will have shut down before the other has finished reporting. The controller then doesn't know the difference between a StellaZ which has gone to sleep and a transmission problem, so will keep trying to contact the now sleeping StellaZ. In the mean time the next one wakes up, asks for instructions and goes to sleep again when it doesn't get them and you end up with a massive pile up.

    The indigo guys have been very good about tailoring their offering to try and avoid this by just sleeping the StellaZs if one wakes up while its dealing with another (so it should then be first to wake up next and so only misses one report). But that means you're then looking at potentially 14 mins between giving an instruction to the StellaZ and it receiving it and afaik there is nobody using more than about a dozen StellaZs (and they don't have the communication overhead of room stats on top).

    It may work okay through a controller, but personally I wasn't willing to shell out the cash on the off chance when the protocol clearly isn't designed with that in mind. The problem being it will work fine until you've spent most of the money so you can't even really buy a few to see if its an issue.

  9. #9
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    Quote Originally Posted by TimJWatts View Post
    Thanks - yeah - I did look at Heatmiser.

    But I decided the wiring would be excessive and I'd need to drop wires to a thermal wax actuator at the radiator, or have a motorised zone valve in the feed pipe.

    Then I'd also have to "OR" all the outputs to drive the boiler demand.

    My "ideal" system so far is actually the Conrad FHT - but the simplex comms bothers me (it is rumoured to be unreliable when you get too many, say >8-10 controllers babbling on the air.

    Z Wave looked interesting, having some interoperability and following a standard, yet being simpler (unlike zigbee) but having zigbee's mesh routing (subject to device support).

    I am happy with the Stella-Z valve (the Danfoss is rumoured to be unreliable, seem a report where the owner had to pull the batteries out every few days to get it to talk to the network).

    I'm happy with the choices for boiler control.

    What I would like to find is a Z-Wave version of the FHT80B which is a room timer stat.

    That leaves the system composed of relatively standalone components (save the boiler relay and I can have a spare) - but also with the option to remote control everything.

    I am a *great believer* in fancy systems being able to degrade gracefully in the even of faults. I'd even keep a boiler timer ready and wired and a few TRV heads in case the whole system failed
    I've actually been running a Conrad / HouseHeat / ELV system for maybe 4 or 5 years now and it's proven pretty reliable. I have 10 radiators across 10 rooms with 10 FHT stats and actuators and the boiler control. I also have the FHZ USB controller running with FHEM and a xAP gateway for integration into other HA systems.

    Overall it's been a good experience, each thermostat can be locally programmed and the USB controller / FHEM / xAP gateway give status and control options externally. I've not noticed any communication issues, the actuators on the radiators react pretty quickly to changes on the thermostats. I've got the boiler control to only kick in if an actuator is opened by 8% or more and it's all pretty autonomous.

    With FHEM you have the option of web interface control and iOS and Android Apps plus the xAP gateway gives integration with other HA systems.

    That said, it has one drawback in that the USB controller seems to "queue" any commands you send to it and decides to send them out "when it damn well wants to" This means that it's not *that* great for instantly turning a radiator off or down in reaction to say opening a window or a door.

    I've been looking for a Z-Wave solution myself and am hoping to try some options out soon, but I really want to replicate exactly the same functionality I have at the moment with a completely autonomous system with HA integration overlaid on top.

    Will update this thread if I get any further with a comparable solution!
    Martyn Wendon
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  10. #10
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    Quote Originally Posted by martyn.wendon View Post
    I've been looking for a Z-Wave solution myself and am hoping to try some options out soon, but I really want to replicate exactly the same functionality I have at the moment with a completely autonomous system with HA integration overlaid on top.

    Will update this thread if I get any further with a comparable solution!
    @Martyn: Any luck with your Z-Wave solution? What have you gone for in the Z-Wave range?

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