Safety Concerns Over a Shower Upgrade??

[Pete E]

Hi Folks,

Not been on here for a while, but something came up the other day that has me concerned to the point I thought I would ask here.

A good friend asked me if I would connect up a new electric shower for him. This is an older gent, a farmer, and as much I like to look out for him and his wife, I advised him that for safety sake he needs a qualified electrician to do this...

As I was at the house, I agreed to "have a look" with a view to repeating he needs a qualified spark...

The farm house was supposedly rewired about 10 years ago, but I think he got taken for a ride. In this case , looking at the CU, the current shower is fed of a 32amp MCB with 6mm T&E, but at the shower end, the wiring is on the old colour scheme although I think its still 6mm T&E.

The real problem is the shower he intends to buy (or the one his wife wants!) is 12.5Kw. Would that be safe to run off 6mm T&E/32amp MCB?

After my warning, it seems the "plumber" who has been approached to change the shower says as the wiring is already there, he will change it over and it will be "fine"..

I really like the old gent, and I am hoping that I am worrying over nothing, but is 6mm T&E (especially old T&E) enough for the load or should it be upgraded to 10mm?

Thanks in advance,

Peter

(edited power rating of shower to 12.5Kw due to sausage fingers)

 

[Pete999]

Hi Folks,

Not been on here for a while, but something came up the other day that has me concerned to the point I thought I would ask here.

A good friend asked me if I would connect up a new electric shower for him. This is an older gent, a farmer, and as much I like to look out for him and his wife, I advised him that for safety sake he needs a qualified electrician to do this...

As I was at the house, I agreed to "have a look" with a view to repeating he needs a qualified spark...

The farm house was supposedly rewired about 10 years ago, but I think he got taken for a ride. In this case , looking at the CU, the current shower is fed of a 32amp MCB with 6mm T&E, but at the shower end, the wiring is on the old colour scheme although I think its still 6mm T&E.

The real problem is the shower he intends to buy (or the one his wife wants!) is 12.5Kw. Would that be safe to run off 6mm T&E/32amp MCB?

After my warning, it seems the "plumber" who has been approached to change the shower says as the wiring is already there, he will change it over and it will be "fine"..

I really like the old gent, and I am hoping that I am worrying over nothing, but is 6mm T&E (especially old T&E) enough for the load or should it be upgraded to 10mm?

Thanks in advance,

Peter

(edited power rating of shower to 12.5Kw due to sausage fingers)

Have you worked out what the Amps will be, for a 12.5Kw load at 240Volts? somewhere in the region of 52 Amps, think the 32Amp mcb will be to small as will the 6mm2 TWE, how long is the cable run, what wiring method has been used, lots of consideration to be taken into account for a job like this, you are correct, professional advice and expertise will be needed, the Plumber is an --- for saying it will be OK to continue, in my opinion.
If as you say the 6mm cable changes colour, one of two things could have occurred The cable could be in a Joint box somewhere on the run, or it goes to the isolator and then to the shower, either way the install needs upgrading/rewiring, and certifying, there is no mention of an RCD on the equation so far.

 

[Taylortwocities]

A 12.5KW shower (is it really 12.5??) will pull around 54amps.
Of course it will be perfectly safe, with the current set up, when they turn it on, the 32A MCB will trip and the power will be disconnected. That's as safe as it can be!

So, a much bigger cable, and a much bigger MCB (I hope there's an RCD too?). And a review of if the supply is capable of supplying that amount of current. A survey of the existing loads is necessary, my experience with farmers is that they always sail close to the wind. You may find that they can have a shower, but not keep the lambs warm at the same time.

Your first thought is correct. He needs a qualified electrician

 

[Pete E]

Thanks gents that's much appreciated..I realised that the draw would be in excess of 50 amps, but wasn't sure if I was missing something like "diversity" ...as I say this is way over my pay grade, and just was asking to make sure I wasn't worrying over nothing..

I forget the brand of the shower, but when I looked at the glossy sales blurb they had, it was rated as 12.5Kw...Ironically I don't think she will be pleased with it anyway as I suspect the underlying/ongoing problem is low water pressure..

With regards the "plumber" I don't think he is time served, more just a "handyman" they have to do odd jobs..

I will reiterate the advice already given and hope they heed...

 

[Taylortwocities]

Diversity does not apply to instant heat water heaters of any type. They are either on or off. Showers of that type usually vary the temperature by altering the water flow rate.

They'll need a good mains water pressure/ That needs sorting first, that may make the existing shower useable!

 

[telectrix]

as a rule of thumb, any shower above 9.5kW requires 10mm cable and a higher rated MCB. volt drop is also a consideration if it's a longish run. calcs need to be done considering the installation method. also RCD protection is requried.

 

[Midwest]

As its a farmer, they probably only shower for thirty seconds, once a month each other alternate months. So my money is on the mcb not tripping on overload.

Plumbers right for once.

 

[Pete E]

As its a farmer, they probably only shower for thirty seconds, once a month each other alternate months. So my money is on the mcb not tripping on overload.

Plumbers right for once.

so very cruel!

 

[Dave OCD]

Whenever anyone consults me about a new electric shower most seem fixated on the ridiculous 10.5kW + versions, probably down to clever marketing. I always try my best to steer them towards a maximum of 9.5kW explaining about the current draw, cable needed and running costs, all for very little advantage really. Most people tend to see sense but with some of these showers you could end up needing 16mm cable depending on the installation. Try terminating that properly in a 45a DP wall or pull switch or even at the shower itself, virtually impossible, 10mm is tricky enough.

 

[Midwest]

Electric showers are a misnomer in themselves.

 

[DefyG]

Installed a 11kW unit earlier this year and manufacturers instructions said 16mm!!! (It didn't read as a recommendation either).

 

[Pete E]

Just want to says thanks again for all the advice and to give a follow up...

I popped around there today and I think I got the message across. When I ventured that he will in effect be wasting £400 as the new shower simply won't work, I think that concentrated his mind.

I also suggested he get in a proper plumber to look at the low water pressure issue first, as he might be better considering a small power shower...

Anyway time will tell, as you can only do so much to help....

Thanks again,
Peter