I notice from the central heating diagrams that 4 (and sometimes 5) connections need to be made between the junction box and the programmer. Is there a particular cable for this or is it usually knocked up with a couple of runs of twin and earth?
Thanks
Paul
I've normally seen multiple cables. Frequently, it has been a 2+E for the permanent live and 3+E for signalling/switched lives. Not that I've seen that many installations.
Christian.
Mine (fitted by an electrician) uses a special cable/flex which has lots of different coloured wires. HTH Dave R
If it was situated so you could use flex, then a wholesaler will do multicore flex. Think Maplin do too. But if it's situated some way off, then suitably marked TW&E will be fine. Or Triple & E as used on two way lighting.
They make a special multi-way cable for the job. The wires are quite small so overall the cable size is similar to say a kettle flex. I bought mine in a larger B&Q. I think they call it "central heating control cable" You can use T&Es but its way overkill for the currents involved and too bulky esp behind the programmer.
Multi core flex cables are easy to come by. I recall seeing some in B&Q.
I've noticed you can get 5 core HiTuf fairly easily.
Christian.
There are many multicore flex and cable manufacturers and many different styles of to choose from. This particular one will take mains voltage up to a maximum of 10 Amps which is more than enough for a central heating control panel or timer / programmer installation.
Use of flexible cables and cords is not ruled out provided all the usual relevant requirements are met [521-01-04]. IMO though, it's inappropriate for normal fixed power & lighting wiring where more suitable cables are readily available. For multi-core control wiring (like CH controls) it's quite OK.
Minimum (copper) conductor sizes for all types of cable are defined [Table
52C]:- 1.0 mm^2 for power & lighting circuits
- 0.5 mm^2 for signalling & control circuits
- 0.1 mm^2 for signalling & control cables with 7 or more conductors intended for electronic equipment.
(All conductors must be adequately protected against overheating caused by fault (s/c), and where relevant, overload current.)
When using multi-core cables, colour coding must be observed [Table 51B]:
- 1, 2, or 3-core cables to use the usual brown, blue, green/yellow
- 4 or 5 core cables may use either brown or black for phase (live) (>5 cores is not mentioned, but I'd assume the same)
- cables including plain yellow or green cores are not allowed
- cables including any bi-colour combination other than grn/ylw are not allowed.
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