Unused SWA

[Jako13!]

What is the regs on terminating unused cable or even cores of an SWA cable. I know sometimes we can’t remove the cable completely sometimes due to being impractical.

 

[Andy78]

Unused cores or cables should be connected to earth if they still form part of an electrical installation but are unused.

 

[davesparks]

Unused cores in a cable which has live conductors in it, or unused singles in trunking/conduit which has live conductors in it, should ideally always be connected to earth. This will prevent capacitively coupled (phantom/ghost voltages) or induced voltages appearing on the conductors.

 

[Jako13!]

Unused cores in a cable which has live conductors in it, or unused singles in trunking/conduit which has live conductors in it, should ideally always be connected to earth. This will prevent capacitively coupled (phantom/ghost voltages) or induced voltages appearing on the conductors.

Unused cable all together?
[automerge]1591968359[/automerge]

Unused cable all together? So you would ideally Earth all the cores to earth?

 

[Strima]

Unused cable all together?

Yes and tied to earth. Also worth labelling up as unused.

 

[David Prosser]

I'm not aware of any regulation that requires unused cores to be connected to earth.

Most control panels will have multi core cables coming in/going out where not all cores will be used, they are not connected to earth but labelled and terminiated correctly into din rail terminal blocks.

 

[davesparks]

I'm not aware of any regulation that requires unused cores to be connected to earth.

There is no regulation specifically in BS7671. But it is common sense and best practice to make the unused cores safe, generally being connected to earth achieves this and eliminates any phantom voltage.

 

[Andy78]

I'm not aware of any regulation that requires unused cores to be connected to earth.

Does EAWR regulation 8 cover it ?

Precautions shall be taken, either by earthing or by other suitable means, to prevent danger arising when any conductor (other than a circuit conductor) which may reasonably foreseeably become charged as a result of either the use of a system, or a fault in a system, becomes so charged; and, for the purposes of ensuring compliance with this regulation, a conductor shall be regarded as earthed when it is connected to the general mass of earth by conductors of sufficient strength and current-carrying capability to discharge electrical energy to earth.

 

[David Prosser]

Many cores are left connected to din rails in control panels. I guess it would cover the other suitable means of preventing danger arising.

 

[Jako13!]

Many cores are left connected to din rails in control panels. I guess it would cover the other suitable means of preventing danger arising.

Connect in terminals or connected to earth?

 

[David Prosser]

Connect in terminals or connected to earth?

See post 6

 

[pc1966]

I would vote for connecting to earth and labelling them as spare. Generally lower R2 is always better and if they are terminated sensibly to earth they can be disconnected and used later if needed.

 

[davesparks]

Many cores are left connected to din rails in control panels. I guess it would cover the other suitable means of preventing danger arising.

Aren't these generally ELV cables rather than LV cables so the potential risk from unexpected voltages appearing on conductors is much less?

 

[David Prosser]

Aren't these generally ELV cables rather than LV cables so the potential risk from unexpected voltages appearing on conductors is much less?

Sometime but not always, it’s also 110V signals, motors and other LV equipment. For example a seven core cable but no thermistor or seal leak on the motor.

 

[R-fur]

You can also have CT and VT wiring which are not classified as ELV.
I find it varies from industry to industry, Perochem usually insist on terminating and earthing. most industries try to at least terminate. In the ESI where I do most of my work there is often just no room to terminate so they are often labelled and left in the trunking sometimes there is a separate trunking just for parking spare cores.

 

[davesparks]

Sometime but not always, it’s also 110V signals, motors and other LV equipment. For example a seven core cable but no thermistor or seal leak on the motor.

In which case they should be terminated to earth to achieve compliance with the EAWR as referenced earlier in the thread.

The fact that this is often not done does not indicate that it is correct not to do it, it indicates that a lot of people perhaps don't understand what should be done or why.

 

[David Prosser]

In which case they should be terminated to earth to achieve compliance with the EAWR as referenced earlier in the thread.

No they can be terminated safely, in preventing danger by other suitable means. As referenced earlier.

 

[davesparks]

No they can be terminated safely, in preventing danger by other suitable means. As referenced earlier.

Yes, but what is another suitable means of preventing danger?
Terminating into a terminal does not prevent the conductor from 'becoming charged' in the way that earthing it does.

 

[David Prosser]

How is a core in a cable designed to be charged dangerous if it is becomes charged? Buy being terminated and labelled correctly it can not be mistaken by a competent person (non competent persons should not be entering a MCC or any other electrical equipment without a PTW). If a fault arises it is no more likely to cause danger than if all the cores are used.

 

[Lucien Nunes]

While we're on the subject:
Socapex plug spider.

 

[davesparks]

While we're on the subject:
Socapex plug spider.

Socapex, that wonderful, better than lectriflex, but still a can of worms, pain in the rear end.
Is it rated for 400V or 230V?
Can we run motors through it or can we not?
Should it be 1.5 or 2.5?
Should it be 10A or 16A?
All 6 on one RCD or RCBO's?
Coils, figure of 8, up and down the flyfloor.

 

[David Prosser]

While we're on the subject:
Socapex plug spider.

Nope no, no, no, there can't be any way a ridiculous device like that should exist !

 

[davesparks]

Nope no, no, no, there can't be any way a ridiculous device like that should exist !

But but but, it's industry standard!
White light, PRG, Neg Earth, SLX, etc etc all have hundreds in stock so it must be OK, no?

 

[David Prosser]

You install them first and let me know how they work out !!

 

[davesparks]

You install them first and let me know how they work out !!

So apex plug spiders have been working out just fine for many years, they obviously aren't ideal but what do you suggest as an alternative?

 

[David Prosser]

I suggest they have nothing to do with spare cores in a SWA cable. If you want to use the carry on.

 

[davesparks]

I suggest they have nothing to do with spare cores in a SWA cable. If you want to use the carry on.

It's not that I want to use them, the industry has hundreds of thousands of them in use and convincing anyone to use an alternative would be impossible.

They have a lot to do with spare cores in an SWA, or any other cable, but with increased risks of accidental contact with the unused cores due to the exposed plug pins.

 

[David Prosser]

I don’t see what they have to do with spare cores in a cable. Could you please explain?

 

[Lucien Nunes]

Spiders of both genders are used in entertainment lighting to send six separate 3-wire circuits along an 18-core cable with 19-pin connectors and split them up again at the far end. E.g. it is easier to run ten 18-core cables round a flown truss than sixty 3-core cables.

But, if some 3-pin plugs are energised and others are lying loose, not engaged in sockets, it is possible (and likely) to make contact via the exposed plug pins with unused conductors of cables and multipole connectors in which other cores and pins are energised.

 

[David Prosser]

That interesting and I would imagine a dangerous arrangement. I can’t see them being used on any of my sites.

As there’s still no consensus on a regulation stating the cores must be earthed. I’ll continue to have the spare cores in SWA cables labelled and terminated into MCC din rails as specified by the designers.

 

[Lucien Nunes]

There are also permanently-installed variants where a rack of captive cables with plugs feed into tie-circuits to sockets spread around the building, looking very much like a telephone exchange. A lighting fixture would be plugged into the nearest tie circuit, and the corresponding patch plug connected to the desired dimmer channel. In the days when dimmers were expensive, it avoided wasting channels feeding sockets that were not needed for a particular show. Multiple fixtures in widely-spaced physical locations (but lighting the same area) could also be grouped onto one dimmer without running extension cables between them. One might have 72 tie-circuit plugs that could be allocated to 24 dimmer channels each with two sockets.

In most cases those plug tails would be connected to the fixed wiring (usually singles in trunking) by a rail of DIN terminals, with one layer of insulation between the terminal of one plug and that of the next...

 

[Jako13!]

So connected to earth at the supply side and the other end appropriately terminated in a junction box

 

[Rockingit]

Socapex, that wonderful, better than lectriflex, but still a can of worms, pain in the rear end.
Is it rated for 400V or 230V?
Can we run motors through it or can we not?
Should it be 1.5 or 2.5?
Should it be 10A or 16A?
All 6 on one RCD or RCBO's?
Coils, figure of 8, up and down the flyfloor.

Now I really miss my proper day job ?? ...... feckin' pandemic.