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Replacing wall stat with wireless?

Discussion in 'Electrics UK' started by Roger465, 2 Nov 2018.

  1. Roger465

    Roger465

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    Last winter, I had a new oil boiler & heating controls installed. It was done under the terms of a local authority grant, which did not include a wireless thermostat.

    For various reasons (things like cornicing etc) it wasn’t possible to put the wall stat in my living room, which is pretty much the only room in constant use – so it was installed on the wall in my hall, just outside the airing cupboard.

    Now, the trouble with that is, it works kind of OK, but of course it switches the boiler off and on to suit the temperature in the hall – so I find myself going out to the hall and adjusting it from time to time, as the living room gets too hot or cold.

    Seems to me that the ideal solution would be a wireless stat… however, I’ve given up trying to get electricians or plumbers to come out and do small jobs like this, so want to tackle it myself unless it would be life-endangering to do so :eek:

    Here are some pictures of what I’ve got. Now it *SEEMS* to me that the wall stat is a simple switch (apart from the thermostatic bit obviously), so it just makes and breaks a loop? If so, first question – can I just buy a wireless stat, and substitute its receiver unit (or whatever that bit is called) for the existing wall stat, and it will work in the same way?

    Secondly, I don’t want to have to get into replacing the timer unit (also pictured below) – is that possible? IE, if the wireless stat just makes and breaks the circuit, presumably the new one would be OK with my existing timer control?

    Thanks everybody :D

    20181102_103134.jpg 20181102_102917.jpg 20181102_102856.jpg
     
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  3. SFK

    SFK

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    Roger,
    Cannot recommend this as never used this version, but this is a temp only radio temp gauge that uses Batteries and so should work for you as you have no mains (240V) at old thermostat position.

    https://www.toolstation.com/shop/p7...MIy9fF3Mq13gIVDr7tCh3jiA07EAQYASABEgLhAvD_BwE


    Note that you may have slight issue in that the screws screwing your old thermostat back plate to wall use a square driver.

    SFK
     
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  4. Roger465

    Roger465

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    Thanks - wow that's cheap :eek:

    The cable that goes into the current stat does seem to carry mains though...?
     
  5. DetlefSchmitz

    DetlefSchmitz

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    I've used a Drayton Digistat RF2 for years - still working as required.
     
  6. SFK

    SFK

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    Roger, "The cable that goes into the current stat does seem to carry mains though" is the point of my suggestion of the tool station on.
    [I believe that this one is battery in Both boxes to power them so you do not need mains. BUT Toolstation does not give full details so I am not 100% sure]
    -EDIT... I was wrong , this also needs 240V which you do not have - see message below.

    The "Drayton Digistat RF2" as suggested by Detlef is a great product, but I did not suggest it as one of the boxes needs mains.
    https://www.draytoncontrols.co.uk/sites/default/files/WEB 31-01-18 IG. Digistat+2RF Web PDF.pdf

    SFK
     
    Last edited: 2 Nov 2018
  7. SFK

    SFK

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    Roger,
    Sorry but I am wrong, the Toolstation version also needs 240V to power it, so NOT suitable for you as a direct replacement of your thermostat (unless you can run 240V to it).
    Manual is here:
    http://www.tfc-group.co.uk/assets/graphics/static/RFWRT_instructions.pdf

    Your better option is therefore to put the receiver at the boiler location (next to your the timer unit), connecting the receiver to 240V to power it, and identifying where the current thermostat wires go into Boiler from the wall and use those as the receiver to swtich boiler on and off.

    Sorry again for raising hopes,
    SFK
     
  8. ericmark

    ericmark

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    It seems hard to get wireless thermostats cheap, but first I think you need to understand what it is there for.
    The thermostatic radiator valve (TRV) should control the temperature in every room, it is an analogue device as is the boiler, so theory is each valve slowly opens and closes modulating the heat output of the radiator, this in turn causes the return water temperature to go up or down which in turn tells the boiler how much output is required.

    When every TRV has closed the bypass valve opens and the boiler can't turn down any more so it starts to cycle on/off, however there is nothing to stop it cycling all summer as it stands, so we use a wall thermostat to stop it cycling in the summer. That is all the wall thermostat is for.

    So you want a wall thermostat which once it switches off, needs quite a drop of temperature before it turns on again, it's whole job is to stop the boiler cycling so a high hysteresis is good.

    However wireless thermostats on the cheap end of the market may do what you need, however they don't have fail safe built in, so if battery fails the heating can get stuck on, as you go to the more expensive types, they include a fail safe, but also have anti hysteresis software so increase the cycling of boiler where idea is to decrease it, you have to move to top end of market to find a wall thermostat which reduces the cycling and now we are looking at opentherm where the thermostat does not tell boiler to switch on/off but tells it to modulate it's output.

    So there is a huge jump, simple on/off thermostat in the hall to something like EvoHome which controls each room independent collects the information from the electronic TRV heads and tells the boiler what output is required.

    There is no right and wrong, every house is different. However step one is try to set the TRV see if that works before spending money, if that fails then you have to make the leap of faith, simple electronic TRV heads, electronic heads which will follow or be followed by a thermostat, full integrated control where the head tell the thermostat (I would call it a hub) what heat is required and that thermostat (hub) then tells the boiler.

    So what you are looking at is how much you are willing to pay. The terrier i-temp i-30 will convert the TRV to a programmable electronic TRV and will likely be enough, however if it's not the your binning it to go to next stage, so safe way is EvoHome.

    But cure is good TRV not moving thermostat in most cases.
     
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  9. flameport

    flameport

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    The existing thermostat does have mains power - the blue and brown wires to the left.
    Even worse, some idiot has wired the switched live using the green/yellow wire.
     
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  11. Roger465

    Roger465

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    You serious? It was a qualified electrician that installed it as part of putting in all new heating controls when the grant work was done... it seems to have worked OK for the last year? What are the implications of what you're saying please?

    {EDIT} - what I mean is, is he an idiot because he's used something which will look like an earth wire because of its colour (idiotic, I agree - that's what I assumed it was), or is the wire connected incorrectly?

    Thanks
     
    Last edited: 2 Nov 2018
  12. Roger465

    Roger465

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    Thanks… sorry, I only understood ¼ of what you said, but here’s the simple (naïve?) logic I followed:


    At the moment, the wall stat is in the hall. The hall radiator doesn't have a TRV. I’ve always been told that TRVs aren’t normally fitted in the room where the wall stat is? So, when the hall reaches its right temperature, the stat turns the heat off. Unfortunately, at this stage, the living room is still cold, because the stat has no awareness of the living room temperature, and the living room requires more heat.


    Thus my decision to move the stat to the room whose temperature is most important to me.


    What’s the flaw in my logic please?
     
  13. DetlefSchmitz

    DetlefSchmitz

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    I think your logic is fine - and Eric is getting bogged down in an issue which is only secondary to your situation. Of course your main thermostat should measure the temperature of the room you most want to control.
     
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  14. JohnW2

    JohnW2

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    You seem to be assuming that everyone has TRVs. However, if the wide range of non-thermostatic valves still offered for sale is anything to go by, that assumption is probably significantly off the mark.

    I must say that I've never really understood how TRVs can really do what they say on the tin, given that they are sensing temperature so close to the radiator.

    Kind Regards, John
     
  15. EFLImpudence

    EFLImpudence

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    Until you move the thermostat, turn down (or off altogether) the hall radiator.
     
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  16. Roger465

    Roger465

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    Thanks everybody for your helpful advice. I think, in view of how cheap the Tower unit is, I’ll get one and just try it – if it doesn't do what I want, I’ll get a more expensive one…

    Think you’ve misread my post – mine does use mains ;)

    Anyway, I’m going to try your suggestion :D

    Yes, I have new TRVs everywhere, and they kind of work – but in any house I’ve lived in which has them, I’ve found their effectiveness seems to vary widely between rooms etc. Kind of feels like they’re a fair bit better than nothing, but far from accurate as far as I can see…
     
  17. flameport

    flameport

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    Regulations do not permit using a green/yellow wire for a switched live, or anything else other than an earth connection.
    It also means there is no earth - although the majority of thermostats do not require one.

    It will work as wired and isn't unsafe, but it does suggest whoever installed it either did not really know what they were doing, or did not care.
    At the very least the green/yellow should be oversleeved in brown at both ends.
    Ideally that cable should be removed and the wireless receiver installed next to the wiring centre using more appropriate cable.
     
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