wrote:

First question is: what problem are you trying to fix? Does your

existing CU have rewireable fuses or cartridge fuses?

I do NOT have a problem. I just wish to upgrade from fuses to MCBs.
My fuses are rewireable types.

MCBs do offer greater ease of use, however if you are not having to
rewire fuses on a regular basis then there is only a limited amount to
gained from the change. MCBs represent slightly better protection in
most cases, but not that much in absolute terms assuming the wiring is
in a reasonable state (rewireable fuses are still permitted in the
current wiring regs). If you are looking to improve safety then you may
get more "bang for your buck" making sure you have RCD protection where
it will give best advantage.

The pictures I've seen of MCBs seem to just clip onto a support bar and
have a screw terminal at each side for wires. If they screw to a buss
bar I'd only expect to see one screw terminal for the output to the
ring or spur or whatever.

There are not usually any side connections on MCBs

Take as an example:

http://www.tlc-direct.co.uk/Products/CM7106B.html

The bottom screw and terminal is used to secure the MCB to the busbar.

A busbar is usually comb like:

http://www.tlc-direct.co.uk/Products/MK5590.html

The prongs of the bar poke into the bottom terminal of the MCB and the
screw is done up. The end prog of the bar pokes into the bottom terminal
of an incomer switch or RCD which is fed from the meter tails which fix
into the top connection.

The rear of it clips to the DIN rail, and the top screw is used to clamp
the wires to the circuit.


--
Cheers,

John.

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