Maximum Load on Consumer Unit + 50A MCB for shower?

[AnonymousImport]

Hello, just some advise please...

I've bought an electric shower (10.8Kw) to install in place of the old mixer shower that comes from our combi boiler. I'm fairly happy with the work required (will be using 10mm2 2 core+earth with 50A pull switch). Plumbing appears straightforward too. The one bit I'm NOT clear on is the wiring into the Consumer Unit.
I understand that I'll need a 45A+ MCB with 30mA RCD. However, my consumer unit (which is an older 8-way Wylex) has 100A master switch with 'Maximum Load not to exceed 100A' sticker below. I have 4 MCBs in use in the unit (2 x 5A [lights+mains smoke alarm] and 2 x 30A [cooker + sockets]).

Clearly, the sums say 70A of MCB already installed, so 45A MCB for shower would be a problem. But then I get confused because the other 4 MCBs in the unit which AREN'T wired up (think the previous owner had them in at one point) bring the total installed up to 120A.

What is going to be the best way of getting an MCB + RCD wired in. Could a 45/50A MCB actually be used in the consumer unit, given the above info, then with RCD housed seperately?

Am quite prepared to get an electrician in to fit etc, if not straightforward job, but would appreciate some advance advise so I know what I'm talking about!

Cheers...

 

[AnonymousImport]

your sums are correct, but what your consumer unit really means is 100A at the same time, so unless you turn everything on i shouldnt worry on that one.

How ever with regard to your rcd it is possible to get a "stand alone version" but i would be inclined to get shot of your old consumer unit altogetherhave a new bigger one which is "split" so that the lights are not protected by the mcb (standard on a "split" consumers unit") and ALL your sockets and cooker and shower are. it would be much safer, but obviously it is NOT a diy job,(don't even think about it) get an electrian, but do get several quotes