Novice installing smart thermostat - Drayton Wiser

Discussion in 'Plumbing and Central Heating' started by Mayank Seth, 25 Nov 2021.

  1. Mayank Seth

    Mayank Seth

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    Hi

    I just bought a Drayton Wiser smart thermostat in the Black Friday sales - I've been eyeing up this model for a while due to its API meaning I can geek out on settings, combined with the smart TRVs.

    Looking at the instrallation/wiring diagrams I think I have it figured out but could do with some help on clarifying/confirming.

    At the momnet I Danfoss components that were put in when the house was built in 2012. The system is a 2 heating zone system contrllled with 3 x 2-way ports. Where I think it gets a little wierd is that I have a 2 channel wired controller in the closet with the cylinder, which controls the hot water and CH1 (most of the house). This is linked to a wired thermostat in the hallway.

    I then have a wireless programmable thermostat in the living room which links to a wireless controller in the cylinder closet, which controlls the 2 way port for the radiators in that room. As far as I've ever been able to determine, this living room wireless system cannot fire up the boiler and only controls the 2-way port so that the heating in this room can only be activated when the rest of the house is also on.

    I can't find where the wiring centre for the whole system is! (where are these normally installed? attic? in the boiler itself? behind the plasterboard near the other controllers? A random mystery location)?

    I think the best way of wiring up my new system would be to short the room thermostat to be permanently on, to install the drayton controller where my main wired controller is, to run a wire from where the living room controller currently is to the CH2 on the drayton controller and just to tape off the L/N to the wireless controller unit. Does this sound correct? It sounds messy and I can't help but feel its a bit of a bodge! Should I just get an electrician to come and rewire things properly (beyondd my skill/effort)?

    Thanks for any input!
     
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  3. stem

    stem

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    What you describe is standard set up for a modern 2 zone heating installation. It follows the long established concept of a programmer for heating and hot water, and then, when the building regulations required new builds to have multizones, this was achieved by adding a programable thermostat for the additional zone. If you were moving to a Hive or Nest thermostat, they still work in the same manner, and require two devices; one, for one of the heating zones and the hot water, and another for the second heating zone.

    The Drayton Wiser is different because it does have a 3 channel version, which I assume will be the one you have ordered. It contains the controls for the two heating channels and hot water in a single controller.

    wiser.JPG

    Usually conversion requires a working knowledge of the heating system wiring, its components how they all relate together. This mod often involves considerable rewiring to bring the wiring from the two separate devices together at one place. Unfortunately it's not as simple as simply swapping an existing programmer for another and decommissioning a single existing room thermostat as with a one heating zone / hot water set up. Normally with this type of installation, I usually identify where each cable / wire goes, get rid of any redundant cables and reconnect it up again from scratch. Although what you suggest in concept would work, not a bodge exactly (except for the "tape off" bit. All wiring should be terminated properly), but not professional either.

    The wiring centre is usually located adjacent to the motorised valves, but it doesn't have to be there, the original installer was at liberty to put it wherever they wanted. However, to do what you suggest, you don't need to access it anyway.
    The thermostats and programmers don't actually control the boiler, the motorised valves do that by means of a small microswitch inside each of them. The controls open the motorised valves and when they are open the microswitch is operated and the boiler starts. Obviously the living room valve is opening otherwise you wouldn't get any heat in there, if it doesn't fire the boiler then there is a problem with the living room motorised valve, or its associated wiring.
     
    Last edited: 25 Nov 2021
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  4. Mayank Seth

    Mayank Seth

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    Thanks for the info. I've been looking at the system behaviour a bit further and realised that the zone 2 valve doesn't open at all (regardless of the zone 2 programmeable thermostat state) unless zone 1 is open. When zone 1 is open/the boiler is firing then zone 2 operates per the programmeable thermostat for that zone. Is that normal/expected?
    I think I've come to the conclusion that wiring it "as it should be" is beyond me, but now deciding whether to get a pro to do it properly or whehter to simply keep the zone 2 valve open and just put smart TRVs on thee radiators it feeds (only 2 of them). do you have an idea of cost to get someone to do it properly (have also posted that question on local forum to see eif anyone willing reponds)? Would there be any notable disadvantage in keeping the valve open and just using TRVs for zone control?
    Thanks again :)
     
  5. oldbutnotdead

    oldbutnotdead

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    Not sure where your knowledge of electricity starts or ends, before fitting this new controller it would be well worth the time and effort to draw a schematic of what connects to what.
    The zone 2 only operating when zone 1 is active- that's a choice (or mistake) that was made when the system was installed. If all the rads fed by the zone 2 valve have WiFi TRVs on them then yes that valve becomes redundant, it can either be removed (best option but plumbing required) or disconnected from electricity then latched open with the manual lever (assuming there is a manual lever).
     
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  6. stem

    stem

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    My thoughts exactly (y). Personally I suspect it will be a mistake, no one sane would make that choice, why would you.
     
  7. Mayank Seth

    Mayank Seth

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    Thanks for the responses guys :)
    I'm pretty handy with circuits and wiring diagrams but my knowledge of central heating systems and conventions for household wiring are nil, hence my lack of certainty about what is going on and my wish to find the wiring centre so I can figure out how the system is currently wired!
    Can aither of you shed any light on what the current wiring is likely to be, given the apparent mistake above? I'm wondering if it would even work to take the zone 2 wire to the drayton controller if in the current setup zone 2 only functions when zone 1 is functioning?
     
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  9. stem

    stem

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    One possibility is that Zone 2 thermostat is connected to the switched side of the Zone 1 thermostat, so that it can only switch power to the Zone 2 motorised valve when Zone 1 is 'on'. However, are you sure that the Zone 2 valve isn't opening, or are you assuming it's not because the heating in Zone 2 isn't coming on? I'll explain my thinking. (or try to :))

    There are two motorised central heating valves, one for Zone 1 & one for Zone 2. Both valves have a microswitch inside that operates and start the boiler and pump when the valve is fully open. If the microswitch in Zone valve 2 has failed, this is what will happen: The heating in Zone 2 comes 'on' and the motorised valve opens, but because the microswitch has failed neither the boiler or pump start and Zone 2 doesn't heat up. Then when Zone 1 comes on, the motorised valve for Zone 1 opens and the microswitch in Zone 1 motorised valve operates and starts the boiler and pump. Because the Zone 2 valve is open it now heats up too.

    If this is true, the system is probably wired up correctly, it's just the motorised valve that is at fault. If you have a multimeter and know how to use it safely, here's the test. Switch the heating system so that only Zone 2 is 'on' and the thermostat calling for heat (ie Hot water and Zone 1 off) and look for 230V across the brown and blue wires on Zone 2 motorised valve. If present the wiring is correct, if not it isn't.

    Assuming that there is 230V present, turn the power off and disconnect the orange and grey wires from the Zone 2 motorised valve (note where they go so you can put them back correctly) switch the heating system so that Zone 2 is 'on' and measure the resistance between the orange and grey wires. There should be little or no resistance. If there is resistance the microswitch has failed.
     
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  10. Mayank Seth

    Mayank Seth

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    I haven't yet checked with a multimeter but I'm pretty confident the problem is as I described it - I have judged the opening of the valve based on the slack in the manual overide lever on it. The lever for the zone 2 valve only moves when zone 1 is open. No adjustments to the thermostat can make the zone 2 lever move unless this is the case. Does that cover it?
     
  11. stem

    stem

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    Ah OK, the lever is slack when the valve is open, so if Zone valve 2 isn't opening until the heating in Zone 1 is on, it does look like the wiring is wrong, unfortunately that means tracing back the wiring for Zone 2 thermostat and finding where it originates from.

    If your house is part of a development and there are other identical properties around, it would be interesting to know if your neighbours heating work in the same manner.
     
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  12. Mayank Seth

    Mayank Seth

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    I was worried you were going to say that! Probably should ahve been more pro-active in querying it while the house was still under warranty. Nevermind, I'm pretty confident I can sort it if I can jsut find where the wring goes - hopeful that an afternoon in the attic with a head torch will see some progress :)
    Thanks again
     
  13. stem

    stem

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    Let us know how you get on, it will be interesting to hear the results of what you find.
     
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