K
keen-apprentice
Hi all, long time reader first time poster. I am an apprentice that has mainly done domestic work, but more recently we have been doing commercial jobs (which i much prefer lol), i do really enjoy electrical work and I'm keen to learn more, which means i ask a lot of questions.
The last couple of weeks has been working with SWA's, re-routeing a 70mm 4 core (as in 3 phase conductors and neutral conductor - apologies in advance if my terminology is wrong here) for a sub-mains to a 3 phase distribution board. Also pulling in SWA 10mm 3 core cables (as in phase/neutral/CPC conductors) for the individual circuits that will be fed from said distribution board.
When it came to glanding off the SWA's the electrician i was working with wasn't really interested in answering any questions about using the 70mm 4 core's armour for earth, or what bonding was required for the banjo's on all the smaller SWA's.
So my questions are:
1. The 70mm 4 core SWA sub-mains runs from the plant room main distribution board, to the new TP distribution board. The SWA armour is used as earth for the sub-mains, but what size cable do use as for the fly lead from the gland's banjo to the main earth bar in the new distribution board?
I think the spark i was working with used 10mm, is that large enough given the fact that it is such a short run?
I have had a look through my books, i did a bit of googling, and did a couple of calcs, and after a lot of head scratching using the adiabatic equation i calculated you would need a 13mm cable, which surely would mean you would need a 16mm earth cable not 10mm?
2. He didnt do any bonding for the 10mm SWA's. He just glanded the cables to the distribution board and bolted the banjos down. I can understand his logic that its a metal clad enclosure, so the banjo and main earth bar will have continuity without a fly lead, but I thought all the glands needed to be linked together via their banjo's and then a fly lead up to the main earth bar. Is that correct? If so what size conductor would you use? 10mm for bonding?
3. On a side note he was really struggling to terminate the 70mm phase conductors into the main switch terminals, surely there must be an easier way lol any tips for how it can be done easier? Or do you just have to crimp a lug to the conductors, to reduce the size of the conductors so they can then terminate easily into the main switch terminals?
Sorry for all the questions, but i am finding it hard to get my head round this, i think i have started to confuse myself a bit lol, so it was time to seek advice. Any help/advice to help me understand a bit better would be awesome.
Cheers, KP
The last couple of weeks has been working with SWA's, re-routeing a 70mm 4 core (as in 3 phase conductors and neutral conductor - apologies in advance if my terminology is wrong here) for a sub-mains to a 3 phase distribution board. Also pulling in SWA 10mm 3 core cables (as in phase/neutral/CPC conductors) for the individual circuits that will be fed from said distribution board.
When it came to glanding off the SWA's the electrician i was working with wasn't really interested in answering any questions about using the 70mm 4 core's armour for earth, or what bonding was required for the banjo's on all the smaller SWA's.
So my questions are:
1. The 70mm 4 core SWA sub-mains runs from the plant room main distribution board, to the new TP distribution board. The SWA armour is used as earth for the sub-mains, but what size cable do use as for the fly lead from the gland's banjo to the main earth bar in the new distribution board?
I think the spark i was working with used 10mm, is that large enough given the fact that it is such a short run?
I have had a look through my books, i did a bit of googling, and did a couple of calcs, and after a lot of head scratching using the adiabatic equation i calculated you would need a 13mm cable, which surely would mean you would need a 16mm earth cable not 10mm?
2. He didnt do any bonding for the 10mm SWA's. He just glanded the cables to the distribution board and bolted the banjos down. I can understand his logic that its a metal clad enclosure, so the banjo and main earth bar will have continuity without a fly lead, but I thought all the glands needed to be linked together via their banjo's and then a fly lead up to the main earth bar. Is that correct? If so what size conductor would you use? 10mm for bonding?
3. On a side note he was really struggling to terminate the 70mm phase conductors into the main switch terminals, surely there must be an easier way lol any tips for how it can be done easier? Or do you just have to crimp a lug to the conductors, to reduce the size of the conductors so they can then terminate easily into the main switch terminals?
Sorry for all the questions, but i am finding it hard to get my head round this, i think i have started to confuse myself a bit lol, so it was time to seek advice. Any help/advice to help me understand a bit better would be awesome.
Cheers, KP