So L1 & N through one hole and L2 & L3 through a different hole in a steel enclosure? to me that's a non-compliance with 521.5.1.

The heating effect with relatively small circuits and especially with thin-walled steel is relatively small however. I've seen all four supply conductors entering a fully loaded 100A TPN DB through separate holes and the heating effect has been unobservable (certainly less that the normal heating of the cables themselves). Several hundred amps through one of the old fashioned cast-iron switch-fuses might be quite a different situation though - but the regs don't distinguish, but apply the same principle regardless.

So for me, it's not compliant, but not a disaster. The old school solution was one big hole,with a sheet of paxolin or similar with a slightly smaller hole in it sandwiched in the gap between the two pieces of trunking (or trunking and DB enclosure) to keep the cables away from the sharp edges of the steel. I guess these days a length of flexible grommet strip might be used instead.

   - Andy.

Thanks for your reply! I’m just trying to distinguish where to draw the line on the non compliance.

These circuits then go on to exit and re enter for the connection of kWh meters all in a row but with 2 inch centres via pvc glands to maintain the ip rating of the trunking, then bush  individually into switch disconnecters for each circuit probably 6inches part, then exit again individually in swa cables all glanded in a row a banjo spacing apart.

To me everything apart from the initial pass though the bushes looks normal and compliant but in theory could have the same effect as when the circuits pass through the bushes? 

Thanks for your reply! I’m just trying to distinguish where to draw the line on the non compliance.

These circuits then go on to exit and re enter for the connection of kWh meters all in a row but with 2 inch centres via pvc glands to maintain the ip rating of the trunking, then bush  individually into switch disconnecters for each circuit probably 6inches part, then exit again individually in swa cables all glanded in a row a banjo spacing apart.

To me everything apart from the initial pass though the bushes looks normal and compliant but in theory could have the same effect as when the circuits pass through the bushes?