Shower cable size check

Mark3551

Hi,

I have recently had an electric shower installed. In the past, I would have done this myself however with these part p rules I was told it was illegal for me to do such work and I have to use a qualified electrician.

I used an electrician from the yellow pages but as I was putting the boards back down afterwards in the loft and have noticed that he has used 6mm cable to connect to a 9.8kW (Mira Escape) shower.

Surely, for a 9.8kW electric shower, he should have used 10mm cable as 6mm appears to be right on the very limit for this sort of current, especially as the cable runs behind the tiles?

Before I give him a ring to get this cable replaced, can someone confirm whether 10mm cable should have been used, and 6mm is not adequate.

Many thanks

Mark

espresso

Yes wrong cable for that shower. Just shows how effective these Part P regs are!

:rolleyes:

A 9.8kW shower could draw approx 42A, which is more than the 35A rating for 6mm cable.

Alan50

I normally fit 10.00mm TW/E cable for a shower that size, but you can get away with 6.00mm for short distances from the board.

Its all down to his calculation and certification

BS: 7671 Electrical installations

Current carring capacity: (ccc)

Reference method 4: cable enclosed in insulated wall (ccc=32 amp)
Reference method 1: cable clipped within the property (ccc=46 amp)

The calculation involves other factors which any qualified electrician would be happy to provide

Alan (NICEIC domestic installer) see:https://www.NICEIC.COM

Mark3551

Many thanks both.

Its a fairly long run of cable to get from the consumer unit, up the wall to the top floor, then across to the back of the house and down again - probably around 20 metres although its difficult to measure accurately. The cable also passes up through plastic ducting, across the top of the loft insulation and then behind tiles to the shower.

The cable certainly does get fairly warm in the loft after a short period of use, so I have instructed my family not to use it for the moment. I have not run the shower for any period of time.

I have spoken with him and he is adamant that 6mm is adequate. I have decided that the installation is unsafe, and have given him until Tuesday to fit the correct size cable (and have stopped the cheque).

Also, I believe the regulations say there should be a mechanical switch (e.g. a pull cord) to turn the shower off. At the moment, I can only turn the shower off in the consumer unit - the light on the shower is always on. Is this correct?

Mark

Stephen_Leak

I concur with the use of 10mm2 cable. And yes, if the shower switch is in the bathroom or shower room (and could be used with wet hands), it should be a ceiling-mounted, pull-cord-operated one.

espresso

Surely this "qualified electrician" has not provided you with Part P certification for this work?

Alan50

I would be concerned with a 20mtr cable run and no local isolator switch?
Probably the supplementary bonding within the bathroom has also been omitted
(has earth cables been attached to the metalic services in the bathroom?)

If he will not rectify the work then I would suggest the following:

Locate your Electrical installation certificate to find out which "Self certification scheme" he belongs to for Building regs Part P approval.

If its NICEiC contact them, they will send there area engineer to carry out an assessment of the installation, if its not to standard, they will ask the electrician to correct his work, or after a period of time will ask another NICEIC electrician to rectify the work with no charge to your self

In my experiance make sure he does belong to one of the approved schemes
If not then contact Building control dept for there advice

Please let me know which scheme he belongs too

Regards

Alan (NICEIC domestic installer)