Mark Williams wrote:


If you're extending a 30A ring then the terminals only need to be
rated at 20A each

Hard to justify quite such a penny-pinching way of going about things!
It's not hard to come up with reasonable scenarios in which the
terminals are called on to pass over 20A - e.g. the spur drawing 15A and
other sockets on the ring drawing 15A at such positions as to cause,
say, 2/3 of that load to flow through the JB we're talking of. While
it's imaginable to use 20A terminals safely, and quite possible to louse
up the use of 30A terminals by having too little effective contact area
for the conductors, I'd consider it irresponsible to use anything lower
rated than 30A. In any case the OP (like the half-orphaned growing lad
in the furniture-out-of-the-window "if they're anything kangaroos" joke)
needs all the room he can get, whereas the JB you point to as well as
having only 20A-rated terms has 6 of them taking up the precious room.
And what did you want him to do with the other 3? He only needs E L & N.
Running short strappers to get two of the 6 terms for each of the 3 ways
only reduces the number of cores in each terminal by 1 - you'll still
have two "real" cores and the strapper - and introduces more
connections. Bodgesville magna.

Stefek