# Replacing electric shower

#### paul243

I need to replace an old "Gainsborough 1000" shower with a 10.5 kw Triton.I don't know the rating of the old shower.
The cable seems substantial but how do I tell if it's 10mm or 6mm?
I presume I need 10mm? for 10.5 kw.
The existing shower comes off a 32 amp mcb at the consumer unit. Is that sufficient? ,if not can I simply replace the the mcb with a higher rating? 45 amp? maybe.
If the cable is 6mm what is the highest rated shower I can fit?
The cable run is approx 4 metres.
Many thanks.

32 amps is a maximum of 7.6kW.
Whether the MCB can be changed depends on the size of the cable and how/where that cable is installed.
A 10.5kW shower might be permitted on 6mm² cable, but again that does depend on how the cable is installed.

In most cases, 6mm² cable will have a single solid earth in it, 10mm² will have a stranded earth. However that's not 100%, particularly with older cables.

Measure one of the strands of the cables diameter with a micrometer and calculate the csa using pi d squared upon 4 and multiply by the number of strands.

I don't think you need 10 mm for 10.5 kW, 6mm will do. I also don't think you need a 10.5 kW shower in these days of saving the planet but that is another arguement.

You can't just go up rating MCBs without doing other checks.

32 amps is a maximum of 7.6kW.
Whether the MCB can be changed depends on the size of the cable and how/where that cable is installed.
A 10.5kW shower might be permitted on 6mm² cable, but again that does depend on how the cable is installed.

In most cases, 6mm² cable will have a single solid earth in it, 10mm² will have a stranded earth. However that's not 100%, particularly with older cables.
Thanks for replies.
The old shower is 8.5kw and has been running off a 30amp Wylex push button mcb in a separate box with 3 mcb's, 2x30amp and 1 5amp with no issues.
The mcb's seem to just pull out?
However a label on the box reads "not to exceed 60amps total.
So as it's been ok so far can I simply replace the shower with a new 8.5kw safely?
The (old)cable to the shower has solid earth but the later cable from the isolater switch to the shower has a stranded earth.
Thanks again

Relacing with a new 8.5KW shower is OK. You should not put a 10.5KW shower on that old board. They don't like it up 'em, Mr Mainwairing.

While we are talking about stuff, where is the RCD protection for the shower? Those old Wylex boards do not have the necessary safety protection, and RCD is a must have. The shower instructions will require it.

Relacing with a new 8.5KW shower is OK. You should not put a 10.5KW shower on that old board. They don't like it up 'em, Mr Mainwairing.

While we are talking about stuff, where is the RCD protection for the shower? Those old Wylex boards do not have the necessary safety protection, and RCD is a must have. The shower instructions will require it.

Is it possible to simply replace the large switch with neon in the adjacent airing cupboard with one incorporating an RCD?

Yes.

TTC.

Yes, that's better.

I only looked on Toolstation site as I thought the OP had mentioned them , but I must be mixing up the threads.

Both? if so in which order?
The first is the enclosure, the second is the RCD. But, with respect, if you need to ask then you need an electrician to do this work for you.
In any case, I’ll bet you don’t have a calibrated RCD tester in your garden shed?

The first is the enclosure, the second is the RCD. But, with respect, if you need to ask then you need an electrician to do this work for you.
In any case, I’ll bet you don’t have a calibrated RCD tester in your garden shed?
Touche!
Thanks will get them ordered

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