Why do people twist CPC's?

Sparkingchip: 
 

“TPFO” Twisted Pair Fell Out, so you got good end to end readings on the socket ring circuit, but it failed testing at the socket.

going back those twenty years I remember it had been a long day and I replied “I thought there’s only twisted pair telephone cable, not twin and earth “ the lecturer announced it was time for a break and coffee then we would discuss it afterwards.

Twisting CPCs together was already an out dated idea twenty years ago and “is not encouraged because it makes fault finding and testing more difficult, also there’s effectively only one CPC rather than two increasing the risk of failpure“.

Since then most manufacturers have introduced double earthing connections on socket and other fittings as “Hi integrity earthing“ with the expectation that the CPCs will be connected separately to each of the two earth terminals to create Hi Integrity Earthing within the ring circuit inline with the requirements of the Wiring Regulations.

Back over to you. 

It is better to apply a small twist to two or more C.P.C.s at a socket outlet and then put it into just one earth terminal. They then stay together. That is a much more reliable option in my opinion than just putting conductors singly. They never just fall out using this method. In your example the C.P.C.s fell out of the terminal due to a loose earth terminal, not due to the twisting together. But I would never twist 2.5mm2 solid conductors.

Z.

Sparkingchip: 
 

“TPFO” Twisted Pair Fell Out, so you got good end to end readings on the socket ring circuit, but it failed testing at the socket.

going back those twenty years I remember it had been a long day and I replied “I thought there’s only twisted pair telephone cable, not twin and earth “ the lecturer announced it was time for a break and coffee then we would discuss it afterwards.

Twisting CPCs together was already an out dated idea twenty years ago and “is not encouraged because it makes fault finding and testing more difficult, also there’s effectively only one CPC rather than two increasing the risk of failpure“.

Since then most manufacturers have introduced double earthing connections on socket and other fittings as “Hi integrity earthing“ with the expectation that the CPCs will be connected separately to each of the two earth terminals to create Hi Integrity Earthing within the ring circuit inline with the requirements of the Wiring Regulations.

Back over to you. 

It is better to apply a small twist to two or more C.P.C.s at a socket outlet and then put it into just one earth terminal. They then stay together. That is a much more reliable option in my opinion than just putting conductors singly. They never just fall out using this method. In your example the C.P.C.s fell out of the terminal due to a loose earth terminal, not due to the twisting together. But I would never twist 2.5mm2 solid conductors.

Z.