9Kw Mira Shower

[Idonotknow]

I am replacing my shower with a 9 KW Mira shower. The wiring that is in at present is 6mm2 cable coming from a separate fuse box ( I think its what you call RCD) which has a 35Amp fuse.This goes to a pull down switch in the bathroom ceiling then to the shower still with 6mm wire. Can I use the same set up (wiring) The installation manual keeps refering to BS7671 whatever that is ?

 

[megawatt]

Your lack of knowledge is a little worrying, are you sure you really want to do this?

The 6mm2 cable will need replacing with 10mm2 and you will need a 40A MCB in the CU.

As the work is notifyable, get some help would be my advice

MW

 

[ricicle]

The 6mm2 cable will need replacing with 10mm2

Why?

 

[Cremeegg]

Good advice from megawatt - if you dont know what BS7671 is then you shouldnt even be contemplating this work - all legal issues aside.

To answer your question BS7671 is the British Standard entitled Requirements for Electrical Installations. The Institute of Electrical Engineers Wiring Regulations Sixteenth Edition. At the risk of offending non Christian or atheist electricians it is their bible containing all manner of regulations, tables and requirements. Yours for about £50 new and at over 300 pages long hardly an easy piece of bedtime reading - unless you have insomnia.

 

[megawatt]

It's all I could think of to try and get the OP to seek advice

 

[Taylortwocities]

35Amp fuse

 

[Adam_151]

35Amp fuse

*thinks*

A piece of 30A fuse wire with a bit of 5A fuse wire twisted around it in a 15A BS3036 carrier (from the old water heater)

... Probably

... Maybe

 

[plugwash]

wylex do a 35A cartridge fuse holder.

 

[bernardgreen]

35Amp fuse

*thinks*

A piece of 30A fuse wire with a bit of 5A fuse wire twisted around it in a 15A BS3036 carrier (from the old water heater)

... Probably

... Maybe

NO

The total surface area of the 5 A wire and the 30 A is greater than that of a 35 A wire so there is more cooling and the combination of 5+30 will create something like a 40 A fuse. ( from memory, the calculations are very complicated and assume both wires are the same type of metal )

 

[Idonotknow]

Thanks for all the knowledgable information, I will take your advice and get a qualified electrician in. So much for DIY it never f@*!&* works.

 

[Adam_151]

NO

The total surface area of the 5 A wire and the 30 A is greater than that of a 35 A wire so there is more cooling and the combination of 5+30 will create something like a 40 A fuse. ( from memory, the calculations are very complicated and assume both wires are the same type of metal )

...whoosh

 

[davelx]

Thanks for all the knowledgable information, I will take your advice and get a qualified electrician in. So much for DIY it never f@*!&* works.

Well yes, it does - if you know what you are doing. The problem with electrical DIY is that the consequences of getting it wrong can be lethal - to you, or your family, or whoever buys your house from you.

So, if someone comes along and displays some reasonable level of knowledge of the basic principles, regulations etc, they will generally get help with the detailed and more finicky aspects. But if someone comes along and demonstrates that they have no knowledge at all (which is fine - we can't all know about everything), then we will recommend the safe path of getting an electrician involved, for everyone's sake.

 

[MarkBarl]

Thanks for all the knowledgable information, I will take your advice and get a qualified electrician in. So much for DIY it never f@*!&* works.

Wise move, and never a truer word spoken.
Also, you want an electrician who is registered with a suitable body to self certify work covered Part P, not just a "qualified electrician" subtle difference. often referred to as "Part P registered"

Depending on where the cable is routed, they may have to change this. A 9KW shower is about 39Amps. 6mm cable clipped to a surface is rated at 46A. However if it is running in conduit this reduces to 38A and if buried in the wall reduces to 32A

As previously mentioned, at the very least they will have to change the fuse.

 

[bernardgreen]

So much for DIY it never f@*!&* works.

DIY can work very well.

DIY by un-informed or fool hardy people is the DIY that fails to work properly.