Cable size for a 10.5kw shower

[Willbeforced]

I'm currently fitting a 10.5kw shower where a 7.2kw shower used to be. The problem is the cable is 6mm and not 10mm. The cable run is around 10 metres or less and is not embedded in plaster board or insulation. The cable runs from the fuse box (obviously), under floor boards, through the waste pipe void area and into the loft.
If I fit a 45amp fuse/MCB will it be safe enough to leave the 6mm cable and not replace with 10mm.

What do you reckon??


Thanks

 

[sterose]

I'm currently fitting a 10.5kw shower where a 7.2kw shower used to be. The problem is the cable is 6mm and not 10mm. The cable run is around 10 metres or less and is not embedded in plaster board or insulation. The cable runs from the fuse box (obviously), under floor boards, through the waste pipe void area and into the loft.
If I fit a 45amp fuse/MCB will it be safe enough to leave the 6mm cable and not replace with 10mm.

I think 10sqmm will do fine for a 10.5kw shower. And by 'will do fine', I mean 'is absolutely essential'.

I cannot emphasise enough that you must use 10sqmm for 10.5kw, and probably should use 10sqmm for anything over 8.5kw.

Incidentally, 10m of 10sqmm will not be expensive - i.e. about 15 quid max. for 10m if you go to a wholesaler.

 

[Willbeforced]

Thanks for the advice 'sterose', much appreciated.

Cheers

 

[JP]

It concerns me a little that everyone says you should use a 10mm cable for 10.5Kw showers and yet Mira state in their installation manual for a 10.8Kw shower that 6mm cable will be fine upto 15metres.

Please see pg13 of this document.

JP

 

[JP]

see here

 

[Big_Spark]

jp, 10500 / 230 = 45.67 A at full load.

According to BS7671, 10mm only has a rating of 43A, without allowing for volt drop etc.

Assuming that the shower os often run at 80% power, then your cable must be capable fo supporting a 36A continuous load.

6mm2 is only rated at 32A max loading.

 

[JP]

I wasn't dissbelieving anyone I was just saying it concerns me. What are Mira playing at ?????!!!!!

Surely someone would have a strong case in court against MIRA if the worst should happen.

JP

 

[Willbeforced]

As I've got a family with 2 kids and do not want the house to burn down the safest option would be to re-cable with 10mm, wouldn't it?

Or is this over cautious?? It seems that there is a definite conflict of information.
I'd rather not re-cable as it is a hassle and I've got enough to do.

Why would the Mira shower manufacturer recommend using 6mm at 15m max for a 10.8kw shower? I'm confused!

Thanks for everyones input by the way.

 

[Big_Spark]

OK, the guide is out of date, MIRA are in the process of updating their guides to reflect changes in the Regs etc.

I know as I phoned to find out what was going on

One important piece of information, unless you have one of their new advanced range of showers NO DIVERSITY MUST BE APPLIED TO THEIR LOADING, they run at full power or 50% power only, depending on setting.

That advice comes straight from Mira's Technical Support Unit.

Bit of an eye opener for me actually as I assumed all showers today used thermostatic control, but apparently it's not cost effective in the cheaper units.

Certainly worth remembering.

Try this if your connecting a shower.

 

[securespark]

FWL

Nice website!!

 

[Big_Spark]

FWL

Nice website!!

Thanks, doing myself as I got tired of the cr*p I was presented with by so called experts in HTML!!

 

[securespark]

FWL

Aren't you being a bit harsh when choosing these figures for capacity?

They are the worst-case scenario - method 4.

 

[Big_Spark]

No, you need to assume the worst case scenario as invariably DIYers will not have the knowledge or experience to take into account volt drop or other enviromental correction factors that will have a bearing on the load capacity of the cable.

I will accept that 16mm for 10.5kW is a bit on the large size, and I would be surprised if many use it, but if you follow 7671 then that's what it states for the load in question.

Remember from my post about the Mira shower, you cannot apply diversity to a shower due to the manner of their operation.

I may add a paragraph to highlight this point in the piece to avoid any confusion.

 

[il78]

Just browsing your site, very interesting Jim........are they the usuall charges within your area....as it seems you aint charging enough......

If we put a spark in a van it costs us around £19 an hour and thats just for the spark to sit there......

 

[Big_Spark]

Just browsing your site, very interesting Jim........are they the usuall charges within your area....as it seems you aint charging enough......

If we put a spark in a van it costs us around £19 an hour and thats just for the spark to sit there......

WE make enough money, don't you worry about that.

Many contractors price themselves out of work simply because they do not know how to figure their overheads properly..it isn't an easy matter at all, get it wrong and you lose money.

We pay our guys £15.20 an hour (normal hours), they all hold CIS 4's and thus there is no tax burden on the company for employee's..well except the office staff.

We pay way above the average to ensure we have the best sparks available and to ensure we keep them. We treat them with respect, they are provided with work clothing, which we clean for them, they have the vans and all fuel is provided for the vehicles.

Power tools and plant belong to the company, hand tools to the Guys, if they require a specialist tool for a specific job, we will supply it.

Last year the company made a after-tax profit that we are more than pleased with as it was a 5.9% increase on the previous tax year. Estimates are that this year our profits will have risen by around 11%...accounts being completed at this time so don't know the exact figure.

We don't make HUGE amounts of money, but I make a living from Franklin-Wood and so do my partners.