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Help with smart thermostat wiring please

Discussion in 'Plumbing and Central Heating' started by cammy2207, 9 Jan 2019.

  1. cammy2207

    cammy2207

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    I have an unbranded WiFi thermostat labelled rn004. I'm replacing a Danfoss rmt 230.

    1) The new stat has 2 thin white wires coming from the side, around 5cm long each. Are these for extra temperature readings from floor etc? If so, how do I not use\bypass them so I can just use internal thermometer?

    2) the new stat has L,N,L1,L2. The old stat has 4,5,1,3,2 and is using red live in 1, blue neutral in 4 and yellow switched live in 2. So am I right in thinking it's a straight forward red to L, blue to N & yellow to L1?

    Thanks in advance
     
  2. muggles

    muggles

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    What do the instructions say?
     
  3. cammy2207

    cammy2207

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    Very little. No mention of the 2 white wires protruding...
     
  4. ianmcd

    ianmcd

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    wire colours on heating controls very seldom mean anything, do not assume that the wire colour is L or N or switched
     
  5. cammy2207

    cammy2207

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    I had the place rewired a few years ago heating system and all.

    Nothing on the two white wires?
     
  6. muggles

    muggles

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    14798228.jpg

    Nope, nothing at all I'm afraid. A picture speaks a thousand words, but my crystal ball is all cloudy. Maybe you could provide one or two?
     
  7. cammy2207

    cammy2207

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  8. cammy2207

    cammy2207

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    This is identical...
     
  9. stem

    stem

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    That is a thermostat for electric underfloor heating. Terminals 1 and 2 are shown connected to a 'restive' heating element. And as you suspected the grey wires are for an underfloor probe. You have the wrong thermostat, there is another version with a 'dry contact' for boilers.

    Capture.JPG
     
  10. cammy2207

    cammy2207

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    Yeah. But surely this would still work with a boiler? I'm sure I've seen these underfloor heating stats being used with boiler instead, need to look again.

    What are the differences between dry and non dry contacts?
     
  11. stem

    stem

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    It might work with the boiler, it might not. I depends how it designed internally. It may well have a relay contact and simply switch L and L1. But it may not. Some electric underfloor heating controls provide a variable output to gradually raise & lower the temperature so that the floor doesn't get too hot, but doesn't go completely cold. (A boiler needs a clean on / off). On the other hand, it may need a permanent resistive load to be connected to terminals 1 & 2 in order to work. Then there is the issue of what to do with the thermocouple wires.

    Basically It all depends on how the manufacturer has programmed / configured / designed the unit to work internally, so only they will be able to advise you definitively. However, if it is as simple as you suggest, I wonder why would they would go to the trouble of making different products for different applications if one would do both.

    A "dry" contact is not connected to any internal wiring inside the device, so it is basically an on/off switch that the installer can use to switch any voltage, in that if connected to 24v it will switch 24v. If connected to 230V it will switch 230V.

    A "non dry" contact will have one side of the switch connected to other wiring inside the device, usually the 230V live, so that only the switched live output is available for use by the installer and it would only be 230V.
     
  12. cammy2207

    cammy2207

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    Thanks @stem for the very informative reply. I totally agree with what you said about bothering to make different versions.

    What would happen if I go ahead like I said I would just to give it a try, will it just not work or break the boiler? Or worse?
     
  13. cammy2207

    cammy2207

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    This is part of the description, which is what made me think it would be ok. Screenshot_20190110-142157.png
     
  14. stem

    stem

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    Sorry I can't say, It might be OK, but I can't confirm this because I don't know what it actually provides from terminals 1 & 2, it may be a simple switched 230V output, it does say L1 and N1 after all.

    The description on the app may be generic to the whole range of products, and not item specific, but again I don't know.

    I am a bit concerned that at item with CE marking doesn't have detailed installation information with it, which makes me wonder if it really is CE marked.

    There are several Chinese companies that seem to produce the same thermostats, but in slightly different packaging, but there are 3 distinct types for different applications. Can you not exchange yours for the correct version?

    Capture.JPG

    Or looking at the app there is a 'Send Inquiry' button, why not ask them if it's suitable for your application?

    Alternatively, if you are competent to do so, or know someone that is you could maybe bench test it and see what comes out of 1 & 2 under operational conditions.
     
    Last edited: 10 Jan 2019
  15. stem

    stem

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    I also notice that you have a RMT 230 that you want to replace with this. The RMT 230 can have voltage free switching.

    rmt.JPG

    That means that it can be used with boilers that have 230V controls or 24v controls.

    If your boiler is wired to use 24v then the thermostat you have is definitely not a suitable replacement because it would put 230V on a circuit designed for 24v, the result would not be good.
     
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