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?
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
*Nostalgia isn't what is used to be.
Dave Plowman email@example.com London SW 12
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.
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
Minimum (copper) conductor sizes for all types of cable are defined [Table
- 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
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