Radial circuit branches

[jonnyplatt]

I've fitted two new sockets in a utility room feeding a tumble drier, washing machine and freezer. I've used 4mm cable for the first socket and 2.5mm for the second socket (as a spur).

I was going to connect the 4mm cable as a branch from a socket on n existing 4mm radial circuit installed (by an electrician) in a new conservatory but have noticed that he has connected the conservatory circuit to a new consumer unit which seems to have a 64amp MCB.

Surely a 64amp breaker is too high for a 4mm radial circuit. A 3kw heater is used in the conservatory and I'm concerned that adding a further branch to the radial could overload the 4mm wiring when the drier and washing machine etc are added to the load (12amps heater plus 20amps for the drier and washer and another 10amps for the freezer gives a potential max load of 42amps - in excess of the 25amps which can be carried by the 4mm cable).

I have the option of connecting the new wiring for the drier and washer direct to the conservatory consumer unit but am still concerned about the 64amp MCB.

Finally, if I connect to the new consumer unit directly do I have to get a certificate for a new installation?

Any suggestions/comments welcome

[jonnyplatt]

Querie now sorted