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Topic Title: Terminating SWA
Topic Summary: Earth wire CSA to Earth nut or Banjo
Created On: 04 November 2009 08:25 PM
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 04 November 2009 08:25 PM
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74jools

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Is there a reg that specifies CSA of earth wire when earthing the armour on SWA cable? I'm not talking about when using the armour as the CPC, typical situation i'm thinking of is where 3 core SWA is used for L, N & E, and cable is terminated into plastic enclosure both ends, the armour as extraneous metalwork requires earthing.

Julian
 04 November 2009 08:40 PM
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dg66

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Extraneous condutive parts require bonding,the SWA is an exposed conductive part,which requires earthing.Look in the big red book for minimum size earth conductors.

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Dave(not Cockburn)
 04 November 2009 08:48 PM
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Testit

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Ideally you might take a reading to ensure the conductor can withstand any potential fault current as well...

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 04 November 2009 09:12 PM
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Legh

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Traditionally, the armour is used as a cpc and needs to be terminated at both ends, however, if you use this method you will also need to check that the armour meets the conditions for thermal constraints, ie the adiabatic equation given in 543.1.1

Where a 3 core cable is used on a single phase circuit, the armour is now only used as a protection against damage and should be treated as an exposed conductive part. In this case it only needs to be connected to the MET at one end via a banjo ring (internal installs) or an earthing nut (external installs) (IMO ).

By the way, I was at a trade counter today and somebody mentioned that they had seen 3-core SWA with the colours Brown, Blue and Greeen/Yellow has anybody else seen this colour combination?

Legh

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 04 November 2009 09:15 PM
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Legh

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543.1.3

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 04 November 2009 10:05 PM
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dg66

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Have seen 5 core brown,black,grey,blue& green/yellow.

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Dave(not Cockburn)
 04 November 2009 10:29 PM
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Legh

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Does it does make more sense for cables sizes up to 25mm2, If SWA cable is going to be used in this manner (B,B,G/Y) rather than as is at present, (B,Bl,G)

Legh

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 05 November 2009 07:24 AM
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50spark

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why is the swa a exposed conductive part?. its got insulation around it and a shroud over the gland?

when i run a 3 core swa out to a 3phase motor, i dont want brown, blue, and g/y conductors!!!!

steve
 05 November 2009 07:43 AM
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sparkiemike

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Originally posted by: 50spark

why is the swa a exposed conductive part?. its got insulation around it and a shroud over the gland?


because it fits the definition in BS7671.
because GN8 says it is

It can be touched, gland shrouds are easily removed without a tool, can can also be touched should the cable be damaged e.g. when digging.

EDIT: also I am not sure if the oversheath could be considered insulation, by that I mean is it manufactured to meet the requirements for insulation?

Edited: 05 November 2009 at 07:49 AM by sparkiemike
 05 November 2009 07:56 AM
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paulskyrme

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Originally posted by: 50spark
when i run a 3 core swa out to a 3phase motor, i dont want brown, blue, and g/y conductors!!!!
steve


I'll second that, especially as I was taught that you must not use the g/y for anything other than earth, and you must not oversleeve it!
In fact I read this again somewhere recently, in a document from the ESC/NIC or something like that IIRC.

Most of my time I work without a neutral in the system anyway, with cables of less than 25mm sq normally!

Also remember that the colour codes change when you move from BS7671 to BS EN 60204 which is the equivalent standard for machinery. The only thing that stays without chage is the G/Y and the prohibition of using this for anything other than a protective conductor.

Paul
 05 November 2009 08:29 AM
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MrP

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Paul

514.4.2

On multicore cables the G/Y can be sleeved therefore not restricted to a protective conductor not the best regulation but there

MrP been here one year and two days
 05 November 2009 08:40 AM
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paulskyrme

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Originally posted by: MrP
514.4.2
MrP been here one year and two days


OK, it is there but what you suggest is not how I read it!

Paul
 05 November 2009 08:51 AM
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zeeper

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Is there a reg that specifies CSA of earth wire when earthing the armour on SWA cable?


544.2

I read this as same size as cpc and no less than 4mm, if no mechanical protection.

cable is terminated into plastic enclosure both ends


Dont forget to use the double lock nut with banjo in between.
 05 November 2009 09:14 AM
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sparkiemike

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or Piranha Earth Locking Nuts, makes things very easy.
 05 November 2009 09:18 AM
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MrP

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Paul

514.4.2

States that G/Y single core cables should be used exclusively as a protective conductor Therefore the implication is that multicore cables containing a G/Y can be sleeved

If you compare the equivalent reg in the 16th pre 2004 amendment
single and multicore cables are included
In the 2004 amendment multicore cables were removed and this carries through to the 17th

The situation would suite a standard 3core flex for use with a class 2 fan incorporating a timer or run on, where the G/Y could be sleeved and used as a switch wire

Mr P
 05 November 2009 09:24 AM
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zeeper

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The situation would suite a standard 3core flex for use with a class 2 fan incorporating a timer or run on, where the G/Y could be sleeved and used as a switch wire


I always thought it good practice to run a earth even when not require for the purpose of testing. Although now Im starting to think maybe theres a reg , or maybe an nic thing. puzzled
 05 November 2009 09:27 AM
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zeeper

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makes things very easy.


I always have trouble getting me pipe grips on those little screws. lol
 05 November 2009 02:33 PM
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zeeper

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I always thought it good practice to run a earth even when not require for the purpose of testing. Although now Im starting to think maybe theres a reg , or maybe an nic thing. puzzled


To answer my own question I was thinking of 411.3.1.1 bottom bit
 05 November 2009 04:25 PM
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AJJewsbury

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To answer my own question I was thinking of 411.3.1.1 bottom bit

In the case of a fan fed via a bit of flex, it could be argued that the "point" is the supply end of the flex - so (provided the fan is class II) no need for a terminated earth connection at the fan, nor a CPC in the flex.

- Andy.
 05 November 2009 06:23 PM
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dg66

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In the case of a fan fed via a bit of flex, it could be argued that the "point" is the supply end of the flex - so (provided the fan is class II) no need for a terminated earth connection at the fan, nor a CPC in the flex

Not a very good argument.Would you class the point as being the accessory? I'd say the accessory is the fan enclosure.

-------------------------
Regards

Dave(not Cockburn)
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