stevep pretended :
I have a Triton 8.5kw shower to install but already have a 7.kw in
another bathroom. I have an old consumer unit, with fuses, rated at
60ohms so it would appear that I need to replace it in order to add
another shower unit.

I think you meant 60amps ;-)

You do either need to replace it or add a second CS, neither of which
is a job for an inexperienced DIY'er.

Is this the only option and if so what do I need to get and do I have
to get an electrician to change it? Although I am reasonably competent
I have read of meter tails and breaking electricity borad fuses etc.
which puts me off somewhat!

Even supposing your CS had spare ways in it, it still might not even be
that simple. If both showers are used at the same time, it might well
exceed your incoming supply capability, especially so if you have an
electric oven/hob as well.

Your two showers running simultaneously would draw nearly 70amps, add
20amps on top for lighting plus other loads and your needs could be 80
to 100amps. As a first step in might be worth ringing your electricity
supplier to enquire what the maximum rating of your cut-out is, try and
talk to an engineer, rather than a telephonist. Explain what items you
presently have and what you plan adding. Some diversity is allowed, in
that they do not calculate loading based upon everything being turned
on simulataneously.

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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.org