Earthing Armour

[petersymonds]

Hi. I am installing a 16mm swa cable to a workshop in the garden. I am using 3 core cable so I can use one core as the cpc. I have terminated the swa into a steel box and will run the cores straight through it to the cu. I will run a single earth wire from the cu to earth the box and armour. What size does this cable need to be?

 

[Andy™]

the size as required by 7671

 

[apprentice87]

Hi. I am installing a 16mm swa cable to a workshop in the garden. I am using 3 core cable so I can use one core as the cpc. I have terminated the swa into a steel box and will run the cores straight through it to the cu. I will run a single earth wire from the cu to earth the box and armour. What size does this cable need to be?

What is it that you are doing?? You know that all this is not as simple as you think.....

john..

 

[binky]

so you are fitting an earth bond rather than the main earth as you propose to use a Core for the cpc. So look up bonding sizes.

 

[Murdoch]

I doubt he has a copy of BS7671

 

[Essex1]

so you are fitting an earth bond rather than the main earth as you propose to use a Core for the cpc. So look up bonding sizes.

I think it is earthing the armour rather than bonding the armour. :innocent

 

[binky]

same difference, gets a stripey wire either way :^O

 

[Rob_the_rich]

Why a metal box? Sounds like there will be no switchgear in it at all.

is the metal box in the house or the workshop? If in the house, what is in the workshop?

 

[Davethsparky]

Why a metal box? Sounds like there will be no switchgear in it at all.

is the metal box in the house or the workshop? If in the house, what is in the workshop?

Terminating into a separate metal box can have many advantages. It can act as a spreader box to avoid taking up space inside a CU with the gland and break out from the cable, it can also give a good solid fixing to the termination of the cable if a plastic CU is being used or it allows the SWA to be terminated and dressed fixed in position at an early stage before the Switchgear is fitted. 

Hi. I am installing a 16mm swa cable to a workshop in the garden. I am using 3 core cable so I can use one core as the cpc. I have terminated the swa into a steel box and will run the cores straight through it to the cu. I will run a single earth wire from the cu to earth the box and armour. What size does this cable need to be?

Usually an offcut from the core being used as the CPC is used for the bond to the banjo. 

Strictly it only requires a bonding connection and so it can be sized according to that. 

 

[petersymonds]

Thanks Dave, there's not enough offcut I was thinking at least half the main conductor so 10mm

 

[Davethsparky]

Thanks Dave, there's not enough offcut I was thinking at least half the main conductor so 10mm

Blimey! Someone was tighter than a ducks rear with the ordering on the cable then weren't they! 

What do you mean by the main conductor? That term doesn't have a definition in 7671 as far as I remember, do you mean the earthing conductor or the cpc. Either way I don't understand why you have chosen half of it as the size for the flylead?