electricians opinions please

[stredwizard]

hi all,

i'm installing an 8.5kw electric shower, im stuck at which way to go as regards to connecting it up to the supply.

my original idea was to add an rcbo to the existing cu which has 2 spare ways, its a modern proteus m2 model, but my father in law came round last night and knows a fair bit about electrics as he fits underfloor heating, he says that it would be easier to buy a dedicated shower rcd/mcb consumer unit, I disagree because I will still have to buy a mcb to connect to this or use a Henley block and add another set of tails, which will mean pulling the companies fuse.

who has the right/best idea?

quick background to save all the questions

8.5kw shower
10mm2 cable run to 45a ceiling mounted pull cord switch, across loft space then clipped to the wall then through joists under bath then down to the current cu location below, roughly 7 metres total.

I also know under part 'p' I am not competent to do this and thats fine, my brother installs kitchens for a living and is all up to date, sadly he is busy

opinions please

scott

 

[Iggifer]

rcbo all the way - assuming you have a non-rcd side in your board - otherwise it's pointless fitting an rcbo

if it's a dual rcd board and you want to avoid taking out one of those rcds if the shower trips an rcd, split the tails

 

[ban-all-sheds]

i'm installing an 8.5kw electric shower,

They don't work very well.

the existing cu which has 2 spare ways

And they are not already RCD protected?

8.5kw shower

The important thing to remember with electric showers is that ye cannae change the laws of physics.

The specific heat of water is 4.19J/gK.

An 8.5kW shower will be able to put 510,000 joules per minute into the water.

If we assume a desired temperature rise of 30°C, the amount of water which can be raised by that by 510,000J is:

510000 ÷ 4.19 ÷ 30 = 4057.3g

So your 8.5kW shower, assuming it's working at 100% efficiency, will deliver a flow rate of about 4l/m.

To put that into some kind of perspective I've seen 15l/m quoted as the rate at which most people think "Ooh yes - that's a nice powerful shower".

No electric shower will be able to deliver that, but the higher the power the closer you'll get to something acceptable.

10mm2 cable

Good for the most powerful one you can find.

I also know under part 'p' I am not competent to do this and thats fine

Well it isn't, really - if you aren't competent to do the work safely you mustn't do it.

 

[Taylortwocities]

I also know under part 'p' I am not competent to do this and thats fine, my brother installs kitchens for a living and is all up to date, sadly he is busy

opinions please

Your bro will almost certainly be registered as "limited scope" under CPS rules.
This means that he can only notify work that is associated with his kitchen installation activities (and that he has done himself).
Assuming the shower is not going in a kitchen that he is installing, that's one wangle you cannot pull.

 

[sparkwright]

City Electrical, unfortunately, is about the only place that sells Proteus.

 

[ericmark]

As said instant heat electric is the last resort for a shower. Either stored hot water or gas instant heat is far better.

Assuming no option then even a 3kW under sink water heater will give you a trickle of hot water but really for a shower 8.5kW is still a trickle of hot water.

As to fitting it is simply not worth doing DIY if you want to stay legal. If you want to break the law then yes you can install it. However because you have broken the law getting it tested to be sure it is safe is rather a problem.

This is one thing I have against Part P it has done the same as the USA prohibition laws it has allowed a gang of rouges to trade.

 

[PrenticeBoyofDerry]

I am pondering on the options....
Proteus! Oh dear!

Are you on a low or high water pressure system?

 

[Iggifer]

I hate proteus with a passion, not as bad as Protek though

 

[OwainDIYer]

City Electrical, unfortunately, is about the only place that sells Proteus.

Oh no, that's a good thing.

Can you imagine what it would be like if they were in B&Q?

 

[ban-all-sheds]

This is one thing I have against Part P it has done the same as the USA prohibition laws it has allowed a gang of rouges to trade.

How does a legal requirement to make reasonable provision in the design and installation of electrical installations in order to protect persons operating, maintaining or altering the installations from fire or injury allow rogues to trade?

 

[RF Lighting]

Lack of policing?

 

[JohnW2]

Lack of policing?

I think that BAS's point was that the existence of Part P really has no bearing on rogues trading. As so many times, I think BAS was 'getting at' eric for talking about Part P when he really should have been talking about notification requirements.

Kind Regards, John

 

[ban-all-sheds]

As so many times, I think BAS was 'getting at' eric for talking about Part P when he really should have been talking about notification requirements.

And as so many times you are wrong.

But if you want to introduce notification, how does that requirement allow rogues to trade?

 

[JohnW2]

But if you want to introduce notification, how does that requirement allow rogues to trade?

You would have to ask eric what he actually meant. He clearly didn't mean Part P, per se - since, as you implied, that would have made no sense. As we know, when eric speaks of 'Part P' he usually means notification, so I suspected that was what he meant on this occasion.

I suspect that he was probably suggesting that the advent of notification meant that only unscrupulous ( and maybe 'cheap' and/or incompetent) people would undertake notifiable work in the knowledge that it was not being notified - but, as I said, you'd have to ask him.

Kind Regards, John

 

[sparkwright]

Out of interest, what is so wrong with Proteus?

Used it a few times, not by choice, found their consumer units too 'short' to get all the wires in nicely.

Really bad is it?