A
Adam W
10. If the CPC breaks at some point you still have the CPC from the other leg.radials - pro's
1. no consideration needs to be given to balancing of loads across 2 legs
In a domestic situation you can't be sure of what's going to be plugged in where so that's not a consideration; if anything having a 32A ring makes that more flexible. On a radial the highest current using equipment should be plugged in to the nearest point to the CU which makes it more difficult with a radial, while with a ring you have 2 ways back to the CU.
2. Quicker to test
You still have to plug in to each socket. End to end doesn't take long, quick calculation and you can work out what you should be getting at each socket. Anyone who can't wrap their head around ring final testing probably shouldn't be doing the job in the first place.
3. Quicker to install
Again if you're reducing the capacity from 32A to 20A and thereby cutting out the last leg back to the CU this might be true, but it's not a true comparison. 2.5mm is quicker and easier to install than 4mm.
4. More flexible in cable layout to each point
You still need to run 2 cables either way.
5. Easier to add extra points at later date and with fewer restrictions with regards to where you can extend the circuit
You can spur off a ring. If the circuit is properly designed in the first place you shouldn't need to; a 'tree' arrangement would be a nightmare to find faults on.
6. Less chance of cross connections at the CU
Not with T&E, which would most likely be used in a domestic situation. If you're talking about singles you could say that about cross connection with other circuits.
7. Saves on cable when floors of a property dont require 32A of power , eg 2 bed terrace houses.
As I've said, it depends on the layout of the property. You could have one ring for all the sockets (maybe an extra cct for the kitchen) and split the lighting circuits differently.
8. integrity of the original circuit layout is less likely to be abused or altered by homeowner /diyer.
You could say that about any circuit. You can't account for what a DIYer/DIer is going to do after you've left, but an end to end at the EICR should pick this up.
9. Greater current capacity for the equivalent amount of cable used , eg
how have a ring main for the ground floor of a house - remove the midpoint cable and this leaves you with 2* 20amp radials - so you have a net gain of 8A for exactly no more cable.
You could say the ring option is 'over-engineered' which will give you some extra headroom for volt drop. Remember with a ring you're not splitting the circuit into 2 radials (although you have the option at a later date) so you can allow for greater diversity.
11. You have the option at a later date to split the ring to make 2 20A radials for whatever reason.
12. With a ring you can draw a similar current using less ways on the board.
I said I'd add an extra 1 - turns out I found an extra 3!
That said, I'm not against radials, but they need to be used in an appropriate situation and not blindly used because they're 'the modern way of doing things'.
Sorry for the delay in reply - I went to the pub with my mate instead of sitting at home talking shop on the internet, although to be fair he's a spark as well so we did talk shop.