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Moes underfloor heating thermostat

Discussion in 'Electrics UK' started by Killalot, 17 Dec 2019.

  1. Killalot

    Killalot

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    Hi can someone point me in the right direction on how to wire it up the instructions are useless. The first picture is how the old thermostat was wired up the second picture is taken from the instructions of the new thermostat, GB image is what I've been following. I know where the mains live and neutral go and the temp sensors, its the blue and black from the underfloor heating. Couldn't work out either if I need to put a link from the mains live to link 1 or 2.
     

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  3. stem

    stem

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    You say that you are following the GB image, but first of all, do you actually have the GB thermostat? The wiring is different for each model GA / GB / GC. The instructions are not useless everything you need to know to connect them is shown in the diagram/s.

    Secondly the original thermostat shows that it is rated at 16A. I can't see the rating of the new thermostat. It might be less, if so, you will first need to check that it has sufficient rating for whatever you are connecting it to, otherwise you could overload it.

    The original thermostat has a dry contact (similar to the GC model) but the wiring for the GB is different. So providing that you do have the GB model and it is sufficiently rated for the duty, then:

    The black* neutral wire in the existing thermostat 1 goes to new stat N (3)
    The blue* neutral wire in the existing thermostat 1 goes to the new stat N1 (2)
    The red live wire in the existing thermostat 2 goes to the new stat L (4)
    The black wire in the existing thermostat 4 NO goes to the new stat L1 (1)

    No need for any link, the GB model has this made for you internally.

    * This assumes that the black wire is the incoming neutral as part of the mains supply, and the blue wire is the neutral to the UFH. If it's the other way around they should be transposed.

    The thermistor probe wires go to NTC (5) and (6)

    EDIT
    Do not do that under any circumstances terminal 2 is a neutral.:eek:
     
    Last edited: 17 Dec 2019
  4. Killalot

    Killalot

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    Hi thanks for the reply the seller told me 1 model can be wired for all 3 different types of insulation? Looking at the box its the GA MODEL.
     

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  5. stem

    stem

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    The seller's sort of correct, but you need to determine which version you actually have, because as the drawing you posted shows the wiring is different for each one. The GA thermostat will have this printed on the back of it. The symbol shows that it is primarily designed for controlling a motorised valve generally associated with a 'wet' central heating system.

    GA.JPG

    The box knockout shows that it only has a current rating of 3 Amps (motorised valves don't consume much power). Is 3 Amps sufficient for the load you want to connect to it? The original thermostat was rated at 16 Amps. [you haven't supplied any info about your UFH system, I don't even know if it's wet or electric, although NTC probes are generally associated with electric UFH]

    1.JPG

    Assuming that the current rating is sufficient, and based on it actually being the GA version

    The black & blue neutral wires in the existing thermostat 1 go to new stat 'N' (3)
    The red live wire in the existing thermostat 2 goes to the new stat 'L' (4)
    The black wire in the existing thermostat 4 NO goes to the new stat 'Open' (2)

    No connection is required to terminal (1)

    No need for any link, this model also has it made for you internally.

    The thermistor probe wires go to NTC (5) and (6)
     
    Last edited: 17 Dec 2019
  6. Killalot

    Killalot

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    Hi the underfloor heating is electric. This is the back of the thermostat, can I use it for underfloor electric heating?, thanks for your advice so far.
     

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  8. stem

    stem

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    It depends upon the current consumption of the underfloor heating. If it's a small system rated at 690W or less, then 3A would be OK. If it's larger than that, then no. A typical underfloor heating mat is usually in the region of 150W to 200W per square metre. [which would equate to 600W for a 1.5 metre x 2 metre area] But other types of electric heating can vary. At the end of the day you will have to tell us what the rating of it is; it's your UFH. If you don't know, you would be best advised to take the thermostat back and exchange it for 16A version as per the existing one. Such a version is available according to the info on the box.

    There is a possible exception to the above where a thermostat is used to operate a relay / contractor (they only use a fraction of an amp) The relay will then switch the heating load through heaver rated contacts.
     
  9. Killalot

    Killalot

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    Hi thanks for the great advice I've ordered a 16a one now,best to be safe than sorry
     
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  10. stem

    stem

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    Indeed. Lets see what version it is. You have the wiring info now for types GA and GB.....so it''ll probably be a GC :)
     
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  11. Killalot

    Killalot

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  12. stem

    stem

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    Perfect. A 16A rated thermostat for electric underfloor heating, and it's type GB :)
     
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