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Smart Thermostat and TRVs

Discussion in 'Home Automation' started by m0t, 2 Sep 2021.

  1. m0t

    m0t

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    We currently have a nest that has gone crazy and I've had to turn all the smart features off to stop it trying to heat the house at 3am.

    We've also got a new baby and need to make sure his bedroom is warm enough in the winter months throughout the night when we'd normally have the heating off completely.

    Are the smart TRV systems that can call for heat as needed worth investing in? Do any of them learn how long it takes for individual rooms to heat up?
     
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  3. RandomGrinch

    RandomGrinch

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    This might not be the best answer, but the simplest way (and simple is what you may need when you have a newborn!) will be just to replace the Nest. Our Nest was brilliant when we had our little one. If you have the base unit you can move it around to the room you are using.
    ...and without getting into Mumsnet territory ;) , the NHS recommendations for baby's room temperatures are 16 to 20°C.
    Our problems weren't with heat, but keeping the room cool enough!
     
    Last edited: 2 Sep 2021
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  4. ericmark

    ericmark

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    From what I read the Drayton Wiser TRV heads do have algorithms to work out how long it takes to heat the room.

    Nest have withdrawn support for using them with Energenie TRV's, so it seems when Google took over they lost their way.

    Main question is if you use OpenTherm? If using OpenTherm then looking at Drayton Wiser or Honeywell EvoHome, if not then Hive seems to have a good idea with their "demand for heat" system.

    Also depends on how room with thermostat cools, yes I know looking at heating, but when heating you can control speed by tweaking the lock shield valve, but you can't control cooling, so you want room with thermostat to cool faster than other rooms, as the TRV can't heat a room unless boiler is running.
     
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  5. m0t

    m0t

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    I've got a 5 year old Worcester Greenstar 28 cdi so I think that's got their proprietary connection on it rather than opentherm.
     
  6. ericmark

    ericmark

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    Yep mother had a Worcester Greenstar 28 and there seemed to be no option on hers for any modulating thermostat, and latter versions did, but as you say Worcester Bosch own system which does not include any links to TRV's, so likely the Hive system is best compromise, most central heating is a compromise, but question has to be how many linked TRV's are required, my house the hall cools to slow, so the living rooms starts getting cold before the hall so we leave open doors to dinning room and kitchen so hall cools faster, it would be better if the living room TRV was linked to hall, but I have silly Nest, and not really worth upgrading to Hive so I can have linked TRV heads.

    But mothers house had a hall which cooled faster than rest of house, so with her house stand alone programmable TRV heads were fine, one wall thermostat was enough, its only job being to turn off boiler on a warm day, the hall TRV was set slightly lower than wall thermostat so in winter it never turned off, and the boiler modulated as it was designed to do. I did have a programmer which turned off heating over night.

    For heating the wall thermostat, TRV head, and lock shield valve can be set to compliment each other, it is the cooling which causes the problem, wall thermostat should be in room which cools fastest, but not where there is alternative heat, or outside doors, every down stairs room in my house has an outside door, so I read that as outside door likely to be used, and I have a wood burner in living room, cooker in kitchen, and dinning room is only heated for evening meal, so only place for a single thermostat for me is the hall.

    Mothers hall worked well, when outside door opened the TRV would open and reheat hall fast, but before it got to wall thermostat setting it would turn right down, so keeping boiler running for rest of house. It does seem Hive was designed to get around the way Bosch does not use OpenTherm. Bosch is like the Apple in computers, good system, but will not conform with international agreed standards, like in phones we had iphone and the rest, in boilers we have Bosch and the rest.
     
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  7. RandomGrinch

    RandomGrinch

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    Interesting, and probably explains why Nest suits our house and may not suit others. We have a small terrace with open plan living/dining room and open stair case. No outside doors, or external sources of heat and nest in living room. The temperature is kept to 20°C with the TRV's in the bedroom set slightly lower.
    The house is kept at a very stable and comfortable temperature for the little one (slightly too cold for the rest of us though!).
     
    Last edited: 3 Sep 2021
  8. m0t

    m0t

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    Our house has a south facing garden with big French doors. The kitchen and dining room get hot quickly all year round. The living room and small office on the other side take much longer to get up to temp.

    At the moment the nest is in the hall in the middle but it's not a great compromise and you end up with none of the rooms at quite the right temp.

    The other question I have is about wireless strengh. There's no cable from our boiler to the thermostat and the nest connection to the Base can be shake. There's nothing more annoying than waking up on a cold January morning to find the nest has lost connection and the heating hasn't come on.

    Are any of the options better/worse for connecting to themselves? It's not a big distance to cover but there are two aerated block walls between the boiler and thermostat.
     
  9. RandomGrinch

    RandomGrinch

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    My nest wall mount is wired to the Heat Link. It still predominantly uses WiFi to 'talk' to it, but will use the wires if the WiFi drops out.
    I don't think it will hurt to run a cable (depending on the system you go for).
    A WiFi extender might work, but be a bit OTT, just to communicate with a recalcitrant nest!

    EDIT:
    Just been going through my nest manuals, the nest and heat link talk through a 'Thread' network - WiFi extenders will not work.
     
    Last edited: 4 Sep 2021
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  11. ericmark

    ericmark

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    The main reason for using Nest is the heat link and thermostat only requires two wires to charge, and send all info between them. So don't rely on wifi.

    Mothers house was a problem, sun in bay windows, and wind direction resulted in problems, I used two thermostats in parallel to try and stop problems one in hall and one tried first in living room, then it lost connection so moved to kitchen, but the major break through was when I fitted a TRV in the hall, against all I had read.

    Modulating boilers and non modulating boilers work very different, this house does not have a modulating boiler, but with mothers with modulating the main control is the TRV, the wall thermostat is only there to stop the boiler cycling in the summer months. In real terms you don't need a wall thermostat, you could simply use an on/off switch and turn off boiler in the summer.

    So the sequence of events, each radiator has the lock shield valve set so around 15°C difference between incoming and outgoing water. It takes a TRV around 10 minutes to close, so you don't want radiator heating up too quickly, or the TRV can't react fast enough, and the temperature overshoots. My TRV showed target and current and once it had been running for around 2 hours the two should be the same, if the current was over target I closed the lock shield and if under opened lock shield by a very small amount.

    As the TRV closes the water is first pushed though the TRV's still open and then the by-pass valve opens, which returns hot water to boiler, and boiler reduces output, so the radiators are only just warm enough to keep room at set temperature. So heat from other source like the sun, the radiators have not got a lot of stored energy, so can adjust output quickly.

    So I used the report from the TRV TRV_report.jpg to set the lock shield valve. The problem is a mechanical TRV does not have °C on its scale, so I moved the electronic one around to set the lock shield valve. Once lock shield valve set, could put mechanical TRV back, the problem was with a mechanical TRV and lock shield you don't know which one to adjust. So using an electronic with °C you know which to adjust.

    Once all set each room is kept as temperature set, note the wall thermostat has had no part in this up to this point.

    However as the weather warms up, the boiler will hit minimum output, at this point it will start to cycle on/off, anti-cycle software can reduce cycling, basic idea is if it turns on and turns off again quickly increase time between turning off and turning on, and of course the reverse. However this relies on ALL radiators having TRV heads, if any radiator does not have a TRV head, then likely the anti-cycle software will not work, this is down to the boilers built in algorithms.

    However we don't want boiler to cycle all through the summer, so we pick the room kept coolest, and we fit a wall on/off thermostat so as summer arrives it will turn off the boiler.

    So prime candidate is the hall, the TRV in hall is set to 17°C and the wall thermostat to 18°C so in winter the wall thermostat does nothing, but in summer it turns off the boiler.

    We may vary this, using both a programmable TRV and programmable wall thermostat, so both change at same time, so we can set day and night temperatures. But the important thing is the wall thermostat simply switches boiler off at set point, if the thermostat tries to do clever things like using a mark/space ratio to stop over shooting, it can completely mess up the system.

    With a modulating thermostat we are looking at a completely different sequence of events, and also with a non modulating boiler.

    Also we must look at geofencing, having the boiler turn off, or at least down to a anti freezing setting, while the property is empty is clearly going to save money, however the big question is how much? I found my house does not cool that fast, and setting geofencing caused over shoot when it tried to reheat the house, if using Drayton TRV heads which have algorithms to work out how long it takes to reheat the room, may well work, but I found cheaper TRV heads delayed the re-heat so actually better not using the geofencing.
     
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  12. ^woody^

    ^woody^

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    I have Drayton Wiser, and it does that.

    There are settings to have the room up to temperature at the time set, not come just on at that time as is more common, and it learns how long the room takes to heat up plus it takes account of external temperatures (from local weather stations/forecast)

    You can see a graph to show you how it's performing compared to how it's supposed to be performing.

    If you have an openthem boiler, it will modulate the heat so that rooms keep a more even temperature, and not cycle the boiler on an off all the time. It does this by keeping the boiler on for longer, but varying the water temperature.

    Generally it works OK, but not perfect according to their own graph. For some reason, I have some rooms that work according to the settings (ie heat up by the designated time and keep a level temperature graph line), whilst two other rooms don't. Drayton have never found out why.

    It's good if certain family members are up early for work, so their rooms can be heated ready.
     
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  13. SoftTopGeek

    SoftTopGeek

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    Hello Woody.

    I've been looking at the Wiser kit also.
    What parts have you used? Do you find it needs resetting much, as I had heard that it loses connection to the trvs, and gives trouble.
    I like the idea of it talking to the boiler (Vaillant in my case) with open therm / ebus to run it at a lower flow and return water temperature when near set point.
    We have a DHW cylinder to control too, so two motorised valves.
     
  14. CBW

    CBW

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    You'dbe better with Vaillant controls vs a n other.
     
  15. ^woody^

    ^woody^

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    I have the room stat controlling two room TRV's and TRVs on all other rads. I have a combi, so no cylinder.

    There was a connection issue on the rad furthest from the Wiser control box (several walls rather than distance I suspect) this gave errors with keeping to the schedule and other on-off issues, so the Tech team recommended using one of their remote plugs to act as a repeater half way. Problem was there was nowhere "half way" to plug the plug into!

    Anyway, the location I ended up using seemed to resole the issue but there is no way of knowing if the rad in question has actually connected to the repeater plug or the control box - you have to initials the TRV and the repeater plug in a set way to force the connection - but in the meantime I've turned off the power for various reasons and removed the TRV in question to change batteries so I don't know what it has connected to. Anyway it's working so I'm not bothered.

    A recent update made the TRVs much quieter when they turn on an off, and they are hardly audible now.

    I don't think I've ever had to reset the system. There used to be some delays with the app connecting to the system, but I think that must be sorted now as it seems to connect as soon as the app is opened.

    The only complaint if any, is that the TRV batteries don't last a year as promised. I'm not using premium brands, but not cheap ones either, but still they last about 9 months. Rechargeables can't be used
    Whether its signal related I don't know, but distant TRV's and one that's more obscured by furniture do seem to go sooner than others. I'm just waiting to see if the TRV firmware update has improved battery life.

    A plus point is that the system is locally operated. Others like Hive and Nest I understand have gone down several times at the server end, making the system inoperable.

    Anyway, Wiser was and looks like still is the cheapest of the smart systems with full actual control, unlike say Nest which just operates the whole house. So as a trial may be worth it if it does not work out. I just hope that as time goes on, Wiser does not make the older tech useless when/if it brings out updated products.
     
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  16. SoftTopGeek

    SoftTopGeek

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    Yes I thought that. The Vaillant TRVs seem too expensive though. :(
    Maybe just one of their room smart stats (that uses the eBus) and keep the regular TRVs in the rooms.
     
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  17. SoftTopGeek

    SoftTopGeek

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    Thank you, that's helpful. Battery life another consideration I suppose.
     
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