From a non solar guy, does this look OK

[Top Cat]

If there's a 20A MCB in the 2 way CU then how can the tails be subjected to an overload greater than the rating of the MCB?
In other words, the MCB is your overload protection and the tails are fine.

Think of an 800A busbar chamber with a few 32A switch fuse isolators fed from it. Would you expect conductors rated at 800A to be terminated into the 32A switch fuse?

If the RCD short circuited then the prospective fault current could be thousands of Amps.
Agree to a point about a busbar chamber but the small tails would or should be mechanically protected.

 

[GaryM]

They are mechanically protected - by their outer sheath. No other protection needed, subject to environment.
Many thousands of amps would be great for fast breaking of a protective device that's suitably rated to break the fault current without destroying itself.

 

[xiaoneitie]

yes, it will only have electricity he is using pass through it. the excess will go off to the grid so I'm not right in saying he will be charged for everything he generates. As you say, just no reduction in his bill!

 

[Dan]

Don't mind me while I bump some threads in the solar PV forum. If they're not current or applicable topics, just ignore the threads; they'll drop off the page. If they are, feel free to chip in and chat solar stuff in the solar panels forum.