Online assistance for electrical trade people in New Zealand and Australia Login  |  Register  |   Forgot Password
Assistance for electrical trade people
 

 

 

 


Click here to send Forum Admin a pdf document for publication on this Topic

Documents must be less than 200k in pdf format

Posted By Topic: Using SWA as an earth conductor

Billy
Oct 10 2013 06:47

Is it still acceptable to use the SWA as the earth conductor in hazardous areas or in ant other non hazardous situation?
   

AlecK
Oct 10 2013 08:11

Start at 5.3.2.2
   

Billy
Oct 10 2013 14:20

Thanks AlecK,

5.3.2.1.3 states - Other Materials provided ...\" the conductor resistance is not greater than that for copper... ...the degree of corrosion resistance shall not be inferior to other materials (Copper - Aluminiuim) suitable for the purpose\".
From this I would assume the SWA souldn\'t be used as the earthing conductor because the corrosion resistance would be inferior. Would you agree with that?
Also are you aware of anything in AS/NZS 60079.14 that completely rules out the use of the SWA as the earthing conductor?
   

HazInspector
Oct 10 2013 14:48

I don\'t think there is anything that specifically excludes the use of SWA for protective earths in 60079.14 but the requirements of AS/NZS3000 will also need to be complied with.
One issue would be that for larger cable sizes the amount of SWA wouldn\'t be enough to be equivalent to the copper conductor in regards to conductivity.

There is a section within AS/NZS60079.14 that allows SWA (among other things) to be used for bonding (potential equilisation).
   

justsuppose
Oct 10 2013 19:57

is the adiabatic equation re swa earth size done over here??? swa used a lot in uk but its usual to run a half sized earth as well...
   

AlecK
Oct 11 2013 09:11

SWA tends to be galvanised, so is corrosion resistant.


5.3.2.2 (ii) specifically permits use of SWA but subject to 5.3.2.3.

5.3.2.3(b) says you can only use SWA to earth things supplied by that cable.

5.3.3 para 4 says minimum CSA for cable component used as PEC must be such that impedance is no greater than for a copper PEC, so a bit of research will find the ohms per km of the copper (sized from Table 5.1) and the cable supplier should be able to provide the ohms per m of the SWA.
   

Mince
Oct 17 2013 15:24

SWA should never be used as an earth continuity conductor, but should always be earthed - I have always held the view that the armour is for mechanical protection only, not for electrical continuity - and always use a suitable SWA gland to terminate an armoured cable.
   

AngryClient
Oct 17 2013 21:12

^^^Citation needed.
   

Apprentice
Oct 17 2013 21:34

No citation required for personal views on \"best practice\".
   

Sarmajor
Oct 18 2013 08:21

AlecK has provided sufficient citations in his post.
The issue with SWA as an earthing conductor is that the SWA cannot meet the requirements of this section in larger cables:
5.3.2.1.3 states - Other Materials provided ...\" the conductor resistance is not greater than that for copper.
   

AngryClient
Oct 19 2013 00:00

Ahh so Mince was just being contradictory for shits and giggles...

I get it.
   

CoopzNZ
Oct 20 2013 20:56

Its never been acceptable to use SWA as an earth
   

daniel2
Oct 20 2013 21:35

I agree with Mince.
   

Sarmajor
Oct 21 2013 10:36

It don\'t really matter what you think about SWA as an earth conductor.

It was used in the past as an earth conductor under some of the conditions noted above and continues to be used as an earth conductor for many installations especially in older industrial situations.

And will continue to be used until someone deems it to be electrically unsafe.
That is the hurdle that must be overcome as it complied when it was installed.
   

AngryClient
Oct 22 2013 11:44

I want to know what CoopzNZ would do if he was installing to a certified design that was using SWA as protective earth conductors.

Enlighten me?
   

CoopzNZ
Oct 27 2013 12:59

Show me a \"certified\" design calling for SWA to be used as an earth conductor