down sizing long lighting circuit

[robhawk]

I'm testing a car park lighting circuit at 200m long. 4mm singles to first point at about 100m and then reduces down to 2.5mm. Trunking used as additional CPC to reduce Zs values. How would you record that on a test sheet? And is there a regulation about downsizing?

 

[Marvo]

I wouldn't see a problem with downsizing cabling as long as Zs is okay and the OCPD is suitably sized for the smallest cable CSA.

 

[robhawk]

Ok. But on the test sheet will I put it as a 2.5mm circuit on schedule of test results, and then put in a deviation explaining 4mm to first point for design section to sign.

 

[Badged01]

Go for your worst case and record it as 2.5mm for the circuit. If its compliant overall then there is no issue with this.

In any remarks column (or notes sheet) record the downsizing of the cable so its obvious on any future inspections what has happened within the design of the system.

 

[spark 68]

The 4mm for the first half of the run is more than likely for VD reasons rather than CCC, it sounds as though it has been properly designed.