Wiring for Thermostat Receiver

grumbler

Ben1989 said:

grumbler said:

In this case your original cable is fine and so would be 1mm2 equivalent or 4-core round flex.

So the normal earth, live, neutral cored flex?

No.  As Risteard said, you cannot use 'earth' core for "comms". To do this correctly, you need 3-core and earth, and the earth wire will be redundant.

Check B&Q - they possibly sell it by metres.

Ben1989

Can I ask why you can't use earth for comms? Surely it's the same type of wire and will conduct exactly the same? What if I were to sleeve it?

https://www.screwfix.com/p/time-3183tq-white-3-core-2-5mm-flexible-cable-5m-coil/207jy#product_additional_details_container

grumbler

Ben1989 said:

Can I ask why you can't use earth for comms? Surely it's the same type of wire and will conduct exactly the same? What if I were to sleeve it?

https://www.screwfix.com/p/time-3183tq-white-3-core-2-5mm-flexible-cable-5m-coil/207jy#product_additional_details_container

If you ask me, IMO it's fine to use it if it's marked correctly with a corresponding sleeve. However, here in UK we have probably the most strict in the world electrical regulations and I trust Risteard on this.

FreeBear

Ben1989 said:

Can I ask why you can't use earth for comms? Surely it's the same type of wire and will conduct exactly the same? What if I were to sleeve it?

https://www.screwfix.com/p/time-3183tq-white-3-core-2-5mm-flexible-cable-5m-coil/207jy#product_additional_details_container

2.5mm² is way over the top and you might find that it doesn't fit through the hole and/or the copper wire is too big for the terminals. 0.75mm² would be better suited. e.g. https://www.screwfix.com/p/time-3094y-white-4-core-0-75mm-flexible-cable-50m-drum/95721

Ben1989

How about this one then.

5metres, 1mm2, 3 core + E. £14

https://www.screwfix.com/p/time-3184y-white-4-core-1mm-flexible-cable-5m-coil/74464#product_additional_details_container

FreeBear

https://www.screwfix.com/p/time-3094y-white-4-core-0-75mm-heat-resistant-cable-10m-coil/836pf

4 core, 0.75mm², 10m. Only £6.89.

grumbler

Ben1989 said:

How about this one then.

5metres, 1mm2, 3 core + E. £14

https://www.screwfix.com/p/time-3184y-white-4-core-1mm-flexible-cable-5m-coil/74464#product_additional_details_container

That's the one that I linked above:

grumbler said:

Ben1989

Apologies Grumbler. Never realised the image was the link!

FreeBear

@Ben1989 - Check your messages !

Bendy_House

Ben1989 said:

I need three cores (live, neutral, comms). No earthing required as it’s double insulated.

It’s a Worcester Bosch Greenstar 4000

3 core + E (or '4-core') H05V2V2-F x 0.75 mm2 heat resistant flexible PVC cable, also referred to as 309*Y

Always good practice to connect the earth cable (inside the boiler) as this will afford extra protection to the cable itself, although it should be a very low risk in your situation.

Do you know how to connect this cable inside your boiler? Are you 100% sure?

Both the Live and Switched Live should be sleeved in Brown, and the neutral in Blue. It is very poor practice to use the 'earth' for anything other that what it was designed for, sleeved or not.