Thermostat wiring advice: Honeywell 6360 to BHT-6000

[eitherxor]

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.

Honeywell Diagram for ref:

 

[stem]

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.

 

[eitherxor]

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.

 

[stem]

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.

 

[eitherxor]

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.

 

[stem]

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.

 

[eitherxor]

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.

 

[eitherxor]

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:

And I'm going to link it like this:

With the other wires connected as previously established.

 

[eitherxor]

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.

 

[stem]

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.

 

[ianmcd]

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

 

[eitherxor]

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:

 

[Brian Mcwilliams]

Hoping someone can help me iv done alot of searching around and this post closest to my own problem I'm trying to do same job as op using pretty much same thromoststs only difference is that my old thermostat only has 3 wires have included pics of my old and new

 

[stem]

Your existing thermostat is incorrectly installed. There isn't a neutral connection to terminal 2. So all you have is a live (in T1) a switched live (in T3) plus earth.

The old stat is purely mechanical, so it will work without a neutral, although its accuracy won't be as good as it should be. However, the new thermostat is mains powered so it requires a live and neutral 230V supply.

For future reference, you should have started your own new thread really. Hijacking someone else's post is against the forum rules

 

[Brian Mcwilliams]

so sorry for hijacking post this smart thromstat been cofusing me for weeks and op has same set up. so there no way to poer new thermo with set up wiring as it is