SWA

[astroman]

Hi All,

I want to run some SWA cable from the meter via a connection block and switchfuse to a second consumer unit. I shall be using 16mm2 cable. Should I use 3 core, L N & E then connect the wire sheathing to the earth core or can I use 2 core L & N and use the sheath as the earth, with, of course the correct glands and earth connectors at each end?

Chris

 

[andy]

Hi All,

I want to run some SWA cable from the meter via a connection block and switchfuse to a second consumer unit. I shall be using 16mm2 cable. Should I use 3 core, L N & E then connect the wire sheathing to the earth core or can I use 2 core L & N and use the sheath as the earth, with, of course the correct glands and earth connectors at each end?

Chris

you can use armour as the earth, so you only need 2core

 

[Qedelec]

Sorry to disagree Andy but I would always use 3 core as Steel wire is not as good a conductor as Copper and under fault conditions the armour carrying the fault current will get hot which will prevent disipation of heat from the live condutors and thus the safe current carrying capacity.

Melt down is not to be recommended.

Cost versus safety, I know where I would put my money!!

 

[BJS_Spark]

Agree with Qedelec. I would always use three core and use one of the core's (not the band!) as a CPC along with the armour. This will have the benefit of reducing the R2 resistance due to being in parallel.

 

[Adam_151]

Tables say its not ok, but these can be overridden by the aquadiabetic equation*, but unless you have the equipement to measure PSCC you won't be able to calculate this, use of a core as cpc in parallel to armour is strongly recommended.

*the tables have a built in margin, use of the aquadiabetic equation means you can make things specific to the supply, and thus cut down the margin, though if in doubt use a separate core

 

[ban-all-sheds]

Always assuming, of course, that you do want to export the earth...