Indoor distribution circuits

[Amp David]

Have been working in a small packaging company today along with another local spark, installing a couple of single phase distribution circuits. 99.99% of my work is domestic, so was really along with him to help and learn a bit more at the same time.

The questions I have is why do some guys install 3 core and others install 2 core SWA for the distribution circuit. My 'mentor' today was pulling in 2 cores and using the armour as the CPC, where as existing distribution circuits were do using 3 core with the 3rd core as the CPC.

Is it personal preference or is it a case of if the CSA of the SWA is of the correct size it can be used.

 

[IQ Electrical]

Have been working in a small packaging company today along with another local spark, installing a couple of single phase distribution circuits. 99.99% of my work is domestic, so was really along with him to help and learn a bit more at the same time.

The questions I have is why do some guys install 3 core and others install 2 core SWA for the distribution circuit. My 'mentor' today was pulling in 2 cores and using the armour as the CPC, where as existing distribution circuits were do using 3 core with the 3rd core as the CPC.

Is it personal preference or is it a case of if the CSA of the SWA is of the correct size it can be used.

It's often a bit of both, ECA recommend using all armoured cables as a cpc without the need for a thermal withstand check, with the exception of 400mm 2-coreand 120mm 2-core.
The 120mm was 'within a few percent of the size required' and is recommended to be used due to the low likelyhood of the cable being run at full current carrying capacity.

Using a third core can help where high Zs is a problem.

 

[Amp David]

These circuits were roughly 55 meters long, suppose it all depends on the calcs for Zs then

 

[pushrod]

cost as well? I know you said indoor but i would still have more faith in the long term integrity of a core rather than the armour for R2

 

[Guest123]

Some designers/specifiers/architects etc etc, stipulate the use of an additional core for CPC regardless of armour size compliance.