Does sheathed wire fulfil the 'separation' requirement?

[cl]

For the 50mm (or 2") separation or physical barrier requirement of the wiring regulations does sheathed cable (i.e. T&E or sheathed mains flex) fulfil the requirement?

[ARW]

Chris, it depends on what you are wanting to do. The only 50mm separation in the regs I can think of refer to coms cables and gas pipes.

[cl]

I thought there was a requirement to separate unsheathed (i.e. as in conduit type single conductors) mains wire from signal/low voltage wiring such as telephone wires.

[ARW]

50mm is 50mm and it does not matter if the 230V cables are single or double insulated.

You might have to be more specific. Remember that 230V is classed as low voltage.

Telephone wires are treated differently to ELV cables (eg 12-24V boiler controls) as they are liable to put 230V into a BT line.

[Bob Minchin]

What on earth is the thinking behind this particular rule? Seems daft to me.

Bob

[spuorgelgoog]

Sheathing is irrelevant as it's not insulation; sheathing's there to protec t the insulation from physical damage, which should not occur within condui t or trunking. Therefore cables in conduit or trunking need not be sheathed .

A physical barrier is required for cables of different classes sharing a co nduit or trunking etc unless both cables are insulated for the higher volta ge. This is, I assume, because within conduit or trunking there will be pla ces where insulation is removed from one class of cable to enable connectio n to terminals etc., and separation of circuits therefore relies on the ins ulation on the other circuit.

AFAIK the 2" recommendation for distance between phone and mains cables was to reduce hum and interference on the phone line. For alarm cables there m ay be a vulnerability leading to false alarming from spikes on the mains in ducing spikes on the alarm wiring. It is not required for electrical safety . The mains cables outside conduit or trunking are insulated, and that insu lation is protected from damage by sheathing. They are electrically safe if you run your hand over them, and they are electrically safe if you run an alarm wire next to them.

TheChief wrote:

No, but it's not supposed to. In fact it would be better if the alarm cable broke down quickly and shorted to earth, tripping the protective device.

Owain

[spuorgelgoog]

Possibly lighting hitting (overhead) phone lines?

Owain

[spuorgelgoog]

or a power wire breaking and falling on an phone line - which were uninsulated in t'olden days.

Owain

[Andrew Gabriel]

Mains and comms cables - to prevent interference on the comms. It finally made it into the regs just as comms cables and protocols were designed to be immune from such noise, and as such it's pretty pointless for things like ethernet, although I would still be concerned with a broadband connection because they operate right up to the limits of the chipsets driving them, and noise can have significantly detrimental effects in that scenario.

The separation from gas services has been there much longer.