Shower cable size

KW99 · 27 Jul 2013

Shower Wiring

KW99
27 Jul 2013
2

Hi was just wondering if someone could comment on whether my shower wiring is 10mm or 6mm (pic attached).

It looks to me like 10mm but would like a second opinion.

I am looking to replace my electric shower.

The one I am taking off is rated 8.7kw to 9.5kw (which I assume in plain English means it is a 9.5kw shower)?

As we did not install it I am just making sure the circuit is ok to replace with another 9.5kw shower.

Any advice would be grateful.

Thanks

RF Lighting · 27 Jul 2013

It's always hard to tell from photos, but it looks like 6.0mm² to me.

Is the earth wire from the cable in the green and yellow sleeving a single solid wire, or is it a wire made of several strands?

KW99 · 28 Jul 2013

RF- The earth wire is made up of several strands.

I think they normally use 6mm wire for internals of shower and the feed to the shower from the wall does appear to be larger than that used in the shower itself.

EFLImpudence · 28 Jul 2013

KW99 said:
The earth wire is made up of several strands.

That would mean it is 10mm²

I think they normally use 6mm wire for internals of shower and the feed to the shower from the wall does appear to be larger than that used in the shower itself.

I think you are right.

Everything would appear to be alright.

Is there a 40A MCB or fuse?

Is it RCD protected?

KW99 · 28 Jul 2013

Thanks EFL - That is good news, just hope it goes all the way to the fuse box - hard to tell.

There is a 40A RCB and is protected.

I have read though that a 45A RCB is advisable - will a 40A be sufficient?

EFLImpudence · 28 Jul 2013

KW99 said:
Thanks EFL - That is good news, just hope it goes all the way to the fuse box - hard to tell.

We hope so.

There is a 40A RCB and is protected.

Bit of confusion.

There should be either -
a 40A MCB protected by a 30mA (0.03A) RCCB (40A, 63A, or 80A doesn't matter) or
a 40A, 30mA RCBO which is a combination of both

I have read though that a 45A RCB is advisable - will a 40A be sufficient?

Yes. 9.5kW @ 240V = 39.6A

riveralt · 28 Jul 2013

KW99 said:
Thanks EFL - That is good news, just hope it goes all the way to the fuse box - hard to tell.

There is a 40A RCB and is protected.

I have read though that a 45A RCB is advisable - will a 40A be sufficient?

If the 45A MCB and RCD is what your read in the shower manufacturer's instructions then you should install a 45A MCB and RCD protection.

EFLImpudence · 28 Jul 2013

riveralt said:
If the 45A MCB ... is what your read in the shower manufacturer's instructions then you should install a 45A MCB ...

Let us hope not.

Don't forget the MCB protects the cable and as long as it is higher than the load current it has nothing to do with the shower.

KW99 · 28 Jul 2013

I have not bought the shower yet - just trying to determine if replacing it with a 9.5kw is safe on current set up.

my old shower states 8.7kw to 9.5kw...to be clear does this mean my old shower is 9.5kw (I would think so as it is 9.5KW max load)

I read it elsewhere on this forum that 9.5kw should have a 45a mcb.

EFL - think I was getting my terms mixed up earlier, may post a pic of my fuse box to be sure.

JohnW2 · 28 Jul 2013

EFLImpudence said:
riveralt said:

If the 45A MCB ... is what your read in the shower manufacturer's instructions then you should install a 45A MCB ...

Click to expand...

Let us hope not. Don't forget the MCB protects the cable and as long as it is higher than the load current it has nothing to do with the shower.

I know what you mean - but it is 'something to do with the shower' in as much as if the In of the MCB were less than the design current of the shower, one would have a non-compliant situation on one's hands.

For example (and I realise this would be contentious) if the manufacturer felt that one should be 'conservative' and work with a worst-case design current, occurring with the maximum permissible supply voltage (253V), then a 40A MCB would not be adequate. One could argue that they/we 'should not do that' - but it's worth remembering that we've recently been discussing a case in which it's at least possible that an OP is suffering from MCB trips on a shower circuit because his supply is 'higher than nominal'.

Kind Regards, John

JohnW2 · 28 Jul 2013

KW99 said:
my old shower states 8.7kw to 9.5kw...to be clear does this mean my old shower is 9.5kw (I would think so as it is 9.5KW max load).

I think that almost certainly means that it is 8.7kW at 230V and 9.5kW at 240V - the sums work out roughly correctly.

Kind Regards, John

riveralt · 28 Jul 2013

EFLImpudence said:
riveralt said:

If the 45A MCB ... is what your read in the shower manufacturer's instructions then you should install a 45A MCB ...

Click to expand...

Let us hope not.

Most 9.5kw/8.7kw showers - like the Mira Enthuse (9.5kw) for example come with the instructions to fit 45A MCB.

EFLImpudence said:
Don't forget the MCB protects the cable and as long as it is higher than the load current it has nothing to do with the shower.

Slightly confused here - I thought we had identified that the OP had 10mm ² cable - with a ccc of 63A clipped direct. So there is nothing wrong with their instructions - even 6mm ² clipped direct still comes out at 46A which means the cable ccc is higher than the MCB rating.

EFLImpudence · 28 Jul 2013

riveralt said:
EFLImpudence said:

riveralt said:

If the 45A MCB ... is what your read in the shower manufacturer's instructions then you should install a 45A MCB ...

Click to expand...

Let us hope not.

Click to expand...

Most 9.5kw/8.7kw showers - like the Mira Enthuse (9.5kw) for example come with the instructions to fit 45A MCB.

Why?

riveralt said:
EFLImpudence said:

Don't forget the MCB protects the cable and as long as it is higher than the load current it has nothing to do with the shower.

Click to expand...

Slightly confused here - I thought we had identified that the OP had 10mm ² cable - with a ccc of 63A clipped direct. So there is nothing wrong with their instructions - even 6mm ² clipped direct still comes out at 46A which means the cable ccc is higher than the MCB rating.

But neither we nor the manufacturer knows the cable installation method.

If the shower is less than 40A then the manufacturer has no reason to increase the MCB rating.

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Shower cable size

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