Ring Circuit - 2 x 2.5mm Live Conductors but the CPC has two different leg sizes - 1st leg is 1.5mm and 2nd leg is 2.5mm

Question

Hello 
 
 On an EICR carried out, I found the following below. 
 
 Line Conductors - 2.5mm 
 CPC Conductors - 1st Leg = 1.5mm, 2nd Leg = 2.5mm. 
 
 Although it isn't best practice, is there actually anything wrong/non compliant with the reduced CPC on one of the legs? I can't seem to find any issues with this in the regs. 
 
 Thank you in advance.

OlympusMons · Accepted Answer

you can use the adiabatic equation to determine the minimum CPC size 
 1.5mm CPC in twin and earth has been acceptable for a good while now. 
 So your 2.5mm is probably oversized. 
 I have heard of same size cpc in Irish twin and earth, with i think insulated 2.5mm CPC. Not sure whether it is recognized by BS7671 though. No disrespect whatsover to the Irish of course.

Ring Circuit - 2 x 2.5mm Live Conductors but the CPC has two different leg sizes - 1st leg is 1.5mm and 2nd leg is 2.5mm

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