I'm confused about junction box rules

Thanks. As I said, I'll look into this properly when I have a little time, probably this evening.

However, in the meantime, what does your approach say about the maximum permissible spur length for a spur originating very close to the origin of the ring? - as I said, a small amount of thought suggests that (assume ring midpoint is already at 'maximum Zs') a spur could be half of the distance to mid-point of ring, not one-eighth of that distance.
Yes in my #112 gut feeling which was literally me considering the centre point being a parallel fed device which would be the same as a single cable of ¼ length of the whole ring.
My #121 I did rather foolishly work out the length from loop resistance which did fortunately come up with 25m for a 100m ring.
 
Same here, in the sense that I certainly wouldn't lose any sleep over it if it were my own installation. However, we're talking about the regulations, and advice given to others, and that's obviously rather a different matter.
True, maybe from now on we will have to say what's the Zs at the doner socket?
 
Same here, in the sense that I certainly wouldn't lose any sleep over it if it were my own installation. However, we're talking about the regulations, and advice given to others, and that's obviously rather a different matter.
In previous timesI've put in many temporary supplies, think public entertainment, field day contests etc etc, and sometimes I've had some 'rather long runs' in service. One of my most common tests for VD is to make a COT
 
If you're talking about the OSG, it's not "8 metres" but, rather 1/8 (12.5%) of the distance from origin of ring to midpoint.
Sorry John my bad, not 8Bm but 1/8 as a %age , still dont follow it though and yes some people do insist that the 2m rule does apply from the point or JB on the ring to the spur itself .
 
True, maybe from now on we will have to say what's the Zs at the doner socket?
Well, we theoretically ought to ask but, as you've pointed out, very few people will be able to measure. I suppose that if they had an EICR or EIC which included the circuit in question, they could get a ('probably still roughly the same') figure from that?
 
Yes in my #112 gut feeling which was literally me considering the centre point being a parallel fed device which would be the same as a single cable of ¼ length of the whole ring.
Quite, and that hardly requires any 'working out'! - as you say ¼ of the entire length of the ring, which is the same as what I said (using the language of the OSG), namely ½ of the the distance to the midpoint of the ring. Certainly very far removed from 'one eighth'!
 

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