Can we use the armour of an SWA as the CPC???

[TAFF4]

Hello again sparkies, here is a snippet of my project submitted for 2391-20 qualification regarding minimum size of S= √(1966²×0.1)/46=13.5mm²

Using the table provided by AEI I can see that a 70mm² four core cable has a 131mm² armour CSA, therefore this is perfectly acceptable.
[/I]

This shows that the armouring can handle 10x the amount of fault current that is required....!! no need for seperate CPC ;-)

Please note: values for armour and conductor resistance are from AEI cables, vvv useful!!! as you dont find them in the regs book, OSG etc. (OSG up to 50mm and doesnt show armour resistance.... there is a way of calculating conductor resistance but i cant remember how.....

Was going to post link to AEI site but you need to be a member to view the datasheets.... if anyone wants to see them and needs assistance then let me know

hope this helps AMP DAVID!!!

The AEI table suggest that the 'effective csa of armouring' is 16.38 sq.mm. Which seems closer to the mark and still good enough but not 10 times as good.

I am not criticising the findings but trying to get this to sink into my bald/grey head and have found this thread very useful.

Thank You.

 

[TAFF4]

It would depend on what it is you wish to achive.
If for instance you wish to determine whether the armour of an SWA cable is suficient to be used as a CPC, then I would either use the cable manufacturer's data or perhaps a chart that you feel is reliable, and then apply the adiabatic equation.
If however you wished to determine, whether the armour was suitable to be used as a bonding conductor, I probablly wouldn't bother making the attempt other than as an exercise to prove to someone that the armour is not sufficient.

Got it now.Thanks.

 

[madmac]

Just throwing this in because i'm sick of reading these threads about very basic electrical practise. If you have to ask questions like this then you shouldn't be touching any electrical installation above a 13amp plug!!!

 

[IQ Electrical]

Just throwing this in because i'm sick of reading these threads about very basic electrical practise. If you have to ask questions like this then you shouldn't be touching any electrical installation above a 13amp plug!!!

I don't agree at all, this has been a good thread, especially the points relating to the adiabatic and copper-steel conductivity ratios.

 

[tonys]

Shocking really

 

[Deleted member 26818]

What if the plug is in the loft?

 

[Amp David]

Just throwing this in because i'm sick of reading these threads about very basic electrical practise. If you have to ask questions like this then you shouldn't be touching any electrical installation above a 13amp plug!!!

Nugget!

 

[TAFF4]

Just throwing this in because i'm sick of reading these threads about very basic electrical practise. If you have to ask questions like this then you shouldn't be touching any electrical installation above a 13amp plug!!!

I look forward to your future input with interest.

Try your spell checker on the more taxing issues.

 

[madmac]

@Amp David: Thanks for that eloquent input into the discussion. After all, who knows? maybe i am a "nugget", or maybe i'm just some daft spark that's looking after his and his fellow electricians jobs! Now for the reality check........If guys on here think they are doing some sort of noble gesture by educating the ill-informed fast track sparks out there by giving away our trade secrets and experience, then don't complain when the next job you've priced for at competitive rates is blown out of the water by a fast tracked fake spark, undercutting everyone and saying a big thanks for this oppertunity!!! Just think about it for a second and you'll see who the real nuggets are and pray that you'll always have a secure and non threatened workplace. Oh and TAFF4, i don't need to be great at spelling on a site like this as it's not dangerous......unlike some of the question and answers i've had the misfortune to gaze on here!!!

 

[IQ Electrical]

@Amp David: Thanks for that eloquent input into the discussion. After all, who knows? maybe i am a "nugget", or maybe i'm just some daft spark that's looking after his and his fellow electricians jobs! Now for the reality check........If guys on here think they are doing some sort of noble gesture by educating the ill-informed fast track sparks out there by giving away our trade secrets and experience, then don't complain when the next job you've priced for at competitive rates is blown out of the water by a fast tracked fake spark, undercutting everyone and saying a big thanks for this oppertunity!!! Just think about it for a second and you'll see who the real nuggets are and pray that you'll always have a secure and non threatened workplace. Oh and TAFF4, i don't need to be great at spelling on a site like this as it's not dangerous......unlike some of the question and answers i've had the misfortune to gaze on here!!!

madmac, I think you're missing the spirit of the forum, who are we to 'restrict' certain items of information?

The sizing of SWA for use as a CPC certainly doesn't slot into the 'trade secret' category, it's been the subject of many reports and studies by the IET and ECA!

Then the adiabatic equation, how many blank looks I get when I mention the adiabatic to 'time served' approved electricians, not because they are 'fast tracked fake sparks' but because they never have occasion to use it on a regular basis!

Of course we can all lose contracts to lesser qualified electricians but restricting forum information won't have a drastic effect on that....