Electric shower advice please

TiTheRev

Guys, I am in need of some help!

Our old Mira advance atl has packed up and we will be replacing it very soon, however it seems some regs have changed and we may need to update the wiring and fuses etc just to keep the same kW rated shower?

We are currently running 6mm cable to the shower off a 32a fuse and the mira unit was 8.7kw. For ease of replacement I was thinking i will put an 8.5kw in now but apparently 32a is no longer enough, although 6mm may be?!

A) is it worth uprating the wire along with the fuse?

what's the highest kW version we could get with our current set-up?

C) is there anything else that has changed with the regs?

D) what brands of shower have you had good/bad experience with please. Was considering Triton or Aqualisa as Mira are just astronomically priced :eek:

All thanks in advance. I am hoping to get this ball rolling very soon as it's useless without a shower at home!

southcoastrgi

the regs haven't changed 32a was never big enough, i'd also be worried about 6mm cable as well but that depends on the lenght of cable from the fuse box to the switch/pull switch & onto the shower, I also doubt it is 8.7kw, electric showers have two ratings depending on your supply ie 230v or 240v

the max on a 32a fuse would be 7.2 kw @ 230v

Ectophile

If you do the maths, 8700W / 240V = 36.25A. So a 32A breaker never was right. An 8.5kW shower will be closer, but it's still over 32A.

You've managed to get away with it, because a 32A breaker will probably never trip at 36A. It certainly won't trip in the time it takes for a shower. But that doesn't make it right.

Whether or not a 6mm cable is good enough depends on exactly where it is run. If it's run through insulation, then probably not. Generally, 10mm is preferred as it has a bit of safety margin.

TiTheRev

I am finding plenty of corners cut in this house and the "DIY" efforts were appalling at best!

The cabling is only around 3m long straight from box through the ceiling (to box) and behind some tiles to the shower unit, so maybe 6mm will be ok. Will certainly upgrade the fuse then, but surely the conversion should allow for approx 230v thus requiring 37a fuse? 8.5 would be best then, but could get away with 9?

I'm sure I read something about a dedicated breaker for the shower?

Any recommendations on brand?

Thanks for the info thus far guys

dm20

As others say, it's not just the length of the cable. The current carrying capacity is reduced when bunched with others, buried in walls or surrounded by thermal loft or wall insulation. In theory it's possible to use 6 mm in ideal conditions, but most need 10 mm.

You shower needs a dedicated MCB, which is sounds like it does.
And it must now have RCD protection - does it?
And does it have a switch (usually pull-cord) to isolate the shower?

TiTheRev

There is an external pull cord, so I am guessing the wiring goes from the fuse board up the wall through the conduit to the ceiling, and back from the switch to the shower (may be nearer 3.5m of cable having not considered that before!). It is not bunched with other wires though.

Having spoken to a sparkie mate over the phone he has suggested I would need either a 40a RCBO, or a 40a MCB and replace the main switch for a 2 pole 100a 30ma RCD. Any recommendation on which is easier?