davezawadi:
This statement is without foundation for practical rings, which are very rarely anywhere near maximum length. As RCD protection is mandatory the Zs question is fairly irrelevant, and voltage drop is just inconvenient and again unlikely to be a problem.
Strangely what regulation does it reference? I suppose none.
I think that the OSG should probably be dumped, it has a number of "old wives tale" comments which are not supported, and any electrician should have a copy of the real regulations, which they should know fairly well (in my experience they don't), and I had a few people turn up for an 18th edition course with just an OSG under their arm! They were really surprised when given a copy of the book to use as to how much was not in the OSG.
I really don't think providing lookup tables that err on the side of caution is responsible for many people being unaware of all of the issues that pertain to the 500 or so pages in BS 7671 (plus all of the attendant standards it references).
I think that's a separate debate all together.
davezawadi:
This statement is without foundation for practical rings, which are very rarely anywhere near maximum length. As RCD protection is mandatory the Zs question is fairly irrelevant, and voltage drop is just inconvenient and again unlikely to be a problem.
Strangely what regulation does it reference? I suppose none.
I think that the OSG should probably be dumped, it has a number of "old wives tale" comments which are not supported, and any electrician should have a copy of the real regulations, which they should know fairly well (in my experience they don't), and I had a few people turn up for an 18th edition course with just an OSG under their arm! They were really surprised when given a copy of the book to use as to how much was not in the OSG.
I really don't think providing lookup tables that err on the side of caution is responsible for many people being unaware of all of the issues that pertain to the 500 or so pages in BS 7671 (plus all of the attendant standards it references).
I think that's a separate debate all together.
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