Thermostat wiring advice: Honeywell 6360 to BHT-6000

Discussion in 'Plumbing and Central Heating' started by eitherxor, 26 Oct 2021.

  1. eitherxor

    eitherxor

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    Hello. I understand that this isn't an uncommon sort of question, I did search beforehand but I would appreciate advice on my specific scenario to be sure, please.

    My existing thermostat has 4 wires connected: Earth, Live, and 2 other wires.
    My new thermostat accepts 4 wires, but none of them are Earth.

    That's alright, because I can screw that off into the pattress box I installed. Though this leaves me questioning the positioning of the remaining wires. Live obviously goes to Live. But I'm dubious about where the other connections go. I will add pictures of old and new, but would this be correct:

    Old 1 - New 4
    Old 2 - New 3
    Old 3 - New 2
    Earth grounded to pattress box

    Thanks for any clarification. I don't mind trying my hand at these things, but don't want to blow my boiler or something so I'd rather be sure.

    photo_2021-10-26_02-44-59.jpg photo_2021-10-26_02-45-32.jpg

    Honeywell Diagram for ref:
    [​IMG]
     
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  3. stem

    stem

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    Hi & welcome to the forum

    You are along the right lines but just missed the connection to terminal 1. Here are the connections in tabular form. I hope my interpretation of the wire colours is correct, difficult to be certain from your photo. However it's what the wires are connected to that determines their function, not the colour of their insulation. :)

    Live in old thermostat 1 = New thermostat 4 (L) (Brown Wire)

    Neutral in old thermostat 2 = New thermostat 3 (N) (Grey Wire)

    Switched Live in old thermostat 3 = New thermostat 2 (Black Wire)

    Then add a wire link between the new thermostat terminals 4 (L) and 1 so that they are electrically connected.

    If you are mounting the new thermostat in a metal box, connect the earth wire to the box. If it's a plastic box, the earth connection isn't required, so insulate it safely and tuck it out of the way.
     
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  4. eitherxor

    eitherxor

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    Hello, stem. Thanks for the welcome and the reply. I can do that, I reckon. May I pick your brains on 2 things to be sure I understand:

    As I understood, the "dry contacts" (1 and 2 on new) shouldn't have voltage, so I'll not contradict you but clarify I definitely link from Live (4) to Dry Contact (1), yes?

    And to do that, can I use simple bell wire, specifically this to make the link: https://www.toolstation.com/doncaster-cables-pvc-2-core-flat-flex-cable-2192y/p78948?store=RP

    Ta again. I'm hoping I can get this fitted today so I'll be sure to update with how I get on.
     
  5. stem

    stem

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    With the original thermostat, the switch is directly connected to the live internally, and as you have figured the new switch is 'dry' or 'voltage free' The reason for this is that more recently, some combi boilers have 24v control, and the voltage free contact allows the thermostat to be connected to either voltage, 230V or 24v. As you want to switch mains voltage you get it via the link between terminals (1) and (4)

    Bell wire isn't ideal as you will be connecting it to mains voltage, and bell wire insulation isn't mains rated. However, the cable in the link you have posted is not bell wire and is suitable for mains voltage.
     
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  6. eitherxor

    eitherxor

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    Alright, that makes sense. The switch itself is voltage free but does need a current controlling it. I'll grab that wire -- happy accident with the wrong URL there, glad that'll fit the bill. Thanks again, and I'll update.
     
  7. stem

    stem

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    In the past I've cut a couple of inches off the end of an appliance lead, and used a wire from that, or an extension lead as they often don't have molded plugs on the end.
     
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  9. eitherxor

    eitherxor

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    Stem, if I were to do what, need I make sure that the wire I re-purpose is a solid core or is that irrelevant? I have an odd broken detail sander there but the wire core isn't solid like the product I previously linked.
     
  10. eitherxor

    eitherxor

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    Just to illustrate and keep up with the post, this is what I'm going with:

    I've snipped this from an old appliance lead:
    20211026_120333.jpg
    And I'm going to link it like this:
    20211026_120257.jpg

    With the other wires connected as previously established.
     
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  11. eitherxor

    eitherxor

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    Stem, you little belta. I've managed to get it on and working with the help of your advice, can't thank you enough for that.

    Over the moon with that, though one bit of bad news is that, with the location difference of the wires, the box doesn't have enough leeway to get in the home comfy.

    That's another job, going to move the hole and box up a couple centimetres.
    20211026_133755.jpg 20211026_133746.jpg
     
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  12. stem

    stem

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    Glad it's working. For your safety please make sure that the earth wire is connected to the metal back box, or any metal replacement. :)

    Just a note; I assume that the new thermostat is a programmable thermostat i.e. has time both time and temperature control built in. In which case the existing time control / programmer will need to be set to be permanently 'on' 24/7 to keep the new thermostat powered.
     
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  13. ianmcd

    ianmcd

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    Whatever timer you had before will have to be set to constantly on or your new thermostat wont work
     
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  14. eitherxor

    eitherxor

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    In case anyone is interested in an update, I still have some finishing work to do on the plaster but moved the hole up and it connects and slots in nicely now.

    Earth is grounded to dedicated screw in the metal pattress box, all other wires exactly as previously stated in the thread.

    I have my Drayton programmer next to the boiler as always on, stat kicks in and ticks off perfectly, and of course the best bit is that the boiler reacts.

    I'll touch it up tomorrow, but it's there and doing the trick:
    20211026_205203.jpg
     
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