9.5KW Shower - installer says 6mm T+E with 40Amp RCD is OK

[gazjam]

Getting a 9.5kw shower fitted next Tuesday, and the installer says for a 9.5kw shower you "could get away with" 6mm cable to the main electrical board.

Now, I'm not so sure, and to be honest, I'm starting to wonder if the guy knows himself.

Local tradesman, probably fitted loads of the things, sounds like he knows his stuff over the phone, but when I asked if he will be using 10mm twin and earth cable for the installation, he says "Naa, 6mm is fine."

Now, I checked about online and couldn't get a answer but general opinion is use 10mm stuff - its rated to carry highter ampage etc etc.

Anyone point to BS Standards or building Regs on this stuff?
Any sparks in the room to advise?

The guy sounded spot on until he mentioned the 6mm cable being fine.

The cable used would be about 10 - 13 meters long.

I have read the Regs say for a 9.5 you need 10mm T+E and a 45A RCD.
The guy says 6mm and a 40A RCD.

Should I be concerned?
(Im in Scotland by the way so I dont think Part P applies)


Thanks.

 

[flameport]

9.5kW is either 39A or 41A depending on the voltage it is rated at.
6mm cable is 47A when installed in the most favourable conditions.

So 6mm could be used, depending on how it is installed. However it would be usual to use 10mm which would allow the fitting of a higher rated shower either now or in the future. The difference in price would be minimal.

Did this installer also mention the requirement for an RCD?
Did they check the main protective bonding and the type of supply to your property before quoting for the work?
Are they or the company they work for listed on this website: www.competentperson.co.uk

 

[gazjam]

Thanks for the reply.

My current RCD is rated at 30mA and the installer spoke of fitting an additional 40A RCD just for the shower.

* Did they check the main protective bonding and the type of supply to your property before quoting for the work?

No, the arrangements were made over the telephone, but he says he has fitted showers in my area and is familiar with the house type.

* Are they or the company they work for listed on this website: www.competentperson.co.uk

I have no idea to be honest. He is a local tradesman advertising in the local newspaper. Is there a requirement for installers to be certified, as is the case with Gas fitters and Corgi Certification?

I am unsure about such matters, just want to make sure everythings safe and above board!


Thanks.[/b]

 

[flameport]

People don't have to be registered but if not, then the work needs to be notified to building control before it is started (and a fee of £100+ paid).
(If in Scotland there is a different system).

The shower supply needs a suitable RCD and MCB, fitting both in a small separate unit is a common way to do this.

6mm cable is only rated at 47A if it is installed on the surface of the wall, embedded in the plaster or in open air. If any part of it goes through insulation, conduit/trunking or other enclosed spaces, it's rating is significantly less.
While it possibly could be used, the cost difference between using 6mm and 10mm cable for that length would only be around £10. The MCB/RCD would typically be the same price regardless of them being 40A or some other rating.

'Knowing the house type' isn't good enough, the main bonding needs to be the correct size and actually present.
This should be green/yellow sleeved wires between the main earth (usually in the consumer unit) and the gas & water pipes where they enter the property.
The supply also needs to be capable of handling the extra load of the shower - in most cases it will be, but not all.

 

[RF Lighting]

Something seems not right to me.

I've never yet given a price without actually seeing a job first.

Due to the very serious consequences of this work being done incorrectly, it is a legal requirement for the LABC to be informed of the work.

This can be done directly by an approved domestic installer, who should be listed on the website mentioned earlier, or you can notify the LABC before the work comennces, and pay them their fee to test and inspect the work.

 

[skenk]

OP Says he's in Scotland so installer won't be on competent person website. No requirement for a building warrant for shower installs.

I would say the chances of the installer knowing proper bonding regs - slim to none, having test gear - slim to none, knowing maximum demand guidelines - slim to none.

Will probably put the shower on it's own RCD even if not necessary and likely take a submain to the new shower CU in 6mm leaving the installation with no single point of isolation. Already got an electric shower? No problem he'll add ye another one in.

How much has he quoted you and what does it include?

 

[RF Lighting]

OP Says he's in Scotland so installer won't be on competent person website.

He didn't at the time of our replies

 

[gazjam]

Thanks for all the replies, and yeah, as I didn't know Part P didn't apply in Scotland till later, so I went back and added my Scottishness in my post.
Sorry 'bout that!

He has quoted me £190 9.5kw shower supplied and fitted - A Triton "Rapide" apparently.


*Some more info*
As its for a small bathrooom (barely longer than the length of a bath) the cable required would be quite short.
The Water tank is on one side of the wall, the cupboard with the CU on the other.
He has said it would be a matter of taking the electric cable and running it under the gap beneath the bath and into the cupboard where the CU resides.
On asking for more details I asked that he would be using 10mm cable for the job, to which he said No, 6mm is fine for a 9.5KW shower.

I know next to nothing about electrical installs, but 5 minutes on Google threw that one into doubt.

As far as I know, for a 9.5KW shower, the atandard install is 10mm T+E with a 45A RCD.
I dont want to tell the guy his business, but as its water over electricity I'm taking no chances.

Chaps,
as someone very out of his depth here, but very aware of safety and having an acute aversion to being fleeced, what would you advise in this situation?

I would be comfortable stipulating to the Installer, "I need THIS cable with THIS RCD installed THIS way" if thats what I need to do.

Can I ask your advice on just WHAT I should be stipulating though?
Im not sure what I should be asking for to be honest - I just want a shower fitted!

Not in my habit to tell Tradesmen their business, but something doesn't seem right in a couple of things he says.
Maybe unfair on the guy, I just want to check first.


Thanks you VERY much for any help here.
Gary.

 

[RF Lighting]

Has he mentioned a double pole isolator, and where that would be situated?

 

[gazjam]

No RF,
no mention of that.
I would take it though (perhaps an error on my part!) that the pull string isolator would be a requirement?
Its a small bathroom so perhaps just outside the door or wherever.
Im sure this can be firmed up once he is on site.

Wish I had read up a bit beforehand though...

A "Shopping list" of things to stipulate are installed would be good.
Again though, I don't want to be an arse and tell the guy his job.

*sigh*


Can I ask, what would be the IDEAL way to install in my situation, and what elements should be there?



Thanks again.

 

[securespark]

Myself, I would install 10 milli, fed via a 30mA RCD protected 50A breaker. This means you don't have to worry too much about its route and allow for future expansion.

I would put the DP switch outside the zones, either pullcord inside or a rocker switch outside the room.

IF the existing CU could take the load, I'd feed it from there. If not, a stand-alone unit for just the shower would be my choice, fed into Henley blocks.

Also, you need PEB's (earth bonding to gas & water pipes) and supplementary if not all circuits in the bathroom are RCD-protected.

What size/ type is your fusebox/ CU?

Have you got PEB's & SEB's?

 

[sparkyspike]

Personally I would use a 45A RCBO, a shower isolator and 10mm cable. Not just because 6mm is too small - it sounds like it might be ok - but because you may want to fit a larger shower in the future.

Your installer may well know the type of house you have and may have calculated 6mm to be the correct cable at a previous house. His quote sounds pretty good too. But if you are not happy, then find someone else. It is up to the installer to explain things properly and give you confidence - not up to you to worry about whether he is competent.

 

[gazjam]

The Fusebox is a Wylex WSES 80/2 30mA Trip, 80A load.
There is a sticker on it saying "Total Load not to exceed 100A"

There is one spare slot in the RCD protected group of fuses.Cant he just use the spare slot, or as the Unit states 30mA Trip it isn't up to the task?

The Installer is telling me he would install a seperate RCD for the shower alone - but he has said 40A not 45?

As he is stressing 6mm cable is alright, I wonder if he is used to working with 6mm cable along with 40A breakers.

On initial discussions he tried to disuade me from having a 9.5KW unit fitted, saying the "8.5 was what I needed" and it was when I phoned him back later asking for a 9.5 fit and stating 10mm cable, he told me 6mm was fine.

Thinking about it, I wonder if 6mm cable and a 40w breaker is what he is used to working with - or has in the van - hence the recommendation for an 8.5KW Unit.

How would the Henley blocks come into play? What would they be used for?

RE: PEB's & SEB's,

The only electrical circuit in the bathroom is a pullstring for the ceiling light, I'm not sure what measures are in place.

Thanks for the help!

 

[sparkyspike]

Your shopping list:

1. Tea bags
2. RCD protected breaker or RCBO to 45A
3. 45A Shower isolator (pull cord or wall plate)
4. 10mm cable
5. Shower
6. Plumbing bits
7. Test equipment
8. Additional materials where required (e.g. if bonding is not up to scratch)

 

[gazjam]

Your shopping list:

1. Tea bags
2. RCD protected breaker or RCBO to 45A
3. 45A Shower isolator (pull cord or wall plate)
4. 10mm cable
5. Shower
6. Plumbing bits
7. Test equipment
8. Additional materials where required (e.g. if bonding is not up to scratch)

In that order?

#8: can you expand on that?

As I said earlier, I just want a "plug and play" solution (i.e. get someone in to do the work!), but I'm one of these guys who look into the little details.

Also, I dont want to tramp on the guys toes, HE'S the tradesman after all, not me.