Running SWA and Cat5 in same conduit?

[martin.shaw11]

I would have thought the seperation provided by the outer insulation and the armouring would satisfy the regs.

[:::Jerry::::]

But that's the ambulance chasing lawyer for you though...

[Andy Hall]

Not really

*Every* cable in the duct would have to be insulated to the standard required of the highest voltage.

and phone cable does not meet those requirements.

.andy

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[usenet]

With a slightly different application in mind I was wondering if the armour of SWA would count as 'physical separation'? In my case it's not for being in the same couduit it because I might want a separation of less than 50mm between the SWA and some non-power cables.

[Andy Hall]

No evidence to suggest that it is, Chris

agree that one would have to try pretty hard to breach tghe armour and insulation, but it does say that all cables have to be insulated to the standard for the highest voltage

.andy

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[usenet]

Well in this case they would be as the 'other' cable is an electric fence wire, much more than mains insulation on that. However I still think the regulations require either mechanical separation or 50mm between it and any mains wiring. It would be just as dangerous (if not more so) to have a mains to electric fence fault as a mains to CAT5 fault.

However personally I would feel quite happy running my electric fence wire along close to the SWA, I was just wondering what the regulations said about such a thing.

[Andy Wade]

There's more to it than that. BS 7671 Reg. 528-01-02 allows six ways in which Band I and Band II circuits can be mixed in the same wiring system. To précis, very briefly, these are:

(i) all cables insulated for the highest voltage present;

(ii) cores of multicore Band I voltage cable insulated separately or _ collectively for the highest voltage present;

(iii) cores of Band I circuit separated from cores of Band II circuit by

• an earthed metal screen with current carrying capacity equal to

• that of the largest Band II core;

(iv) compartmented trunking system;

(v) physical separation barrier when cables are on cable tray or

• ladder;

(vi) separate conduit, trunking or duct.

For method (iii) the condition is met by the armour of 2-core SWA cables (to BS 5467) up to an including 10 mm^2. Since the OP mentioned 6 mm^2 SWA the arrangement originally proposed complies with BS 7671.

But I agree that direct burial of the SWA is preferable. It increases the current rating too.

[martin.shaw11]

"unless conductors of the two bands are separated by an earthed metal screen" ie the armour sheath.

[Andy Hall]

OK. I took (iii) as being applicable to metal trunking with a divider

- but I see your point.

Do you happen to have a table reference for SWA current carrying capacities for buried, ducted and clipped to a wall, Andy?

.andy

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[Andy Hall]

Point noted. I had taken an earthed metal screen to be applicable to trunking.....

.andy

To email, substitute .nospam with .gl

[Andy Wade]

BS 7671 Table 4E4A or

latter also gives adiabatic 1 s fault current ratings for the armour.

TBH the current rating is usually somewhat academic since the size normally ends up being determined by voltage drop considerations.

[Steve Walker]

I'm sure that I've seen CAT5 cable rated to 250V. Still not the best solution though.

Steve W