shower

westside · 3 Aug 2005

hi, i have installed a new electric shower 10.8 kw. Wired it to the double pole with 10m2 cable. Its all set bar being connected to the cu.
Reason being i want to know is the mcb high enough for the shower.
MCB is a(mem 32a type b),
cu is 240/415v- 50hz.
the 10m2 cable was already there and a sticker on the mcb saying shower.
will it be alright.
thankful for any advice

comms · 3 Aug 2005

power(kw)/volts(230)=amps

10.8kw / 230 volt = 46.9amp

So no the 32amp mcb will not be sufficient.

westside · 3 Aug 2005

so i need a 46.9amp mcb then.
also could i put it into the cooker mcb as i do not use it.

Adam_151 · 3 Aug 2005

You need a 50A MCB

Please tell us how long this cable is, and what route it takes, and whether you are going to have rcd protection on this circuit,

oh I think I hear something, *listens carefully* sounds like ban shouting something about pee, *replies "not on the CU, ban, would be painful I'd imagine "*

westside · 3 Aug 2005

it`s about 50 ft long
it goes from my sitting room up to the attic then along to the bathroom on the other side of the house ( were i found it taped up).
how do i put a rcd in and were in the cu does it go.

Steve · 3 Aug 2005

easiest way to fit an RCD is to cut the shower cable where it leaves the CU, get a shower RCD mini-consumer unit and fit this in-line with the shower cable. You're sure the entire cable run is 10mm2? It needs to be, given this rating and distance.

Some may argue use 16mm2 cable, and a 63A industrial isolator instead of that pull-switch, but in reality, you're likely to be ok with 10mm, as long as its ventilated (not buried in loft insulation), and the 45A pullswitch.

comms · 3 Aug 2005

Instead of using an rcd you could replace the mcb for a rcbo, this will save you having to install the second shower cu.

BenStiller · 3 Aug 2005

I would put a 45 amp breaker in, and you might not need an rcd, it depends on your earthing system

breezer · 3 Aug 2005

crafty1289 said:
and the 45A pullswitch.

(breezer strokes chin) hmmm

comms said:
power(kw)/volts(230)=amps

10.8kw / 230 volt = 46.9amp

this

westside · 4 Aug 2005

sorry about replying so late, yes it`s defo 10m2 cable and its not covered,
its just lying on the loft floor.
i just found in the cu a elcb,
apart from upgrading the mcb to 50amp, should the elcb be ok
thanks for the input

Spark123 · 4 Aug 2005

What are the current ratings of the ELCB (trip and capacity)? What else does the ELCB supply feed? The reason I ask is to determine if there is enough capacity left in it to run the shower. The 10mm² cable should be good for 64A if installed away from insulation.

mapj1 · 4 Aug 2005

sorry about replying so late,

Its OK, we have gone to bed and will respond tommorrow if you are lucky.

Seriously, with Email and bbs like this no one waits up for you to post, so dont feel guilty. There are some night owls here.
Seriously wait and see if anyone has any more thoughts tommorrow before rushing off. If they don't its probably sensible as alerady said.

ban-all-sheds · 4 Aug 2005

1) Firstly, that rating will almost certainly be a 240V one, i.e. 45A.

2) I know I am well overdue in editing my "This is Part P" document, but DIYnot have not said they'll post it as I suggested, so I think we do have to highlight to westside that if he does this without notifying LABC in advance then he is breaking the law. We may not care, but he might...

3) Westside - you don't know the difference between metres and millimeters, you have no idea of the relationship between voltage, current and power, you have no idea what electrical specifications mean, you don't know how to fit things into a CU and you don't know where an RCD would go in the circuit.

Are you sure you should be doing this job?

westside · 4 Aug 2005

hi people, again sorry for late reply as went to bed cuz got work.
To be honest it`s my wifes dads friend who is a retired electrician and has`nt done work for years.
That`s why i`m asking for answers so i can understand what he is doing.
In the cu the elcb says on it
curent trip rating 0.1a
1th=40a
240/415v 50hz
The elcb wires are only going into the meter.

ban-all-sheds · 4 Aug 2005

westside said:
In the cu the elcb says on it

curent trip rating 0.1a - that's 100mA, better than nothing, but not sensitive enough for a shower - 30mA is recommended
1th=40a - that means it can only interrupt 40A - not beefy enough for the shower, let alone an entire installation, which it probably used to cover
The elcb wires are only going into the meter - so it's disconnected anyway.

So is there no RCD anywhere in the CU?

Do you know what type of earthing your supply has? A 100mA RCD for the whole thing sounds like it might be TT...

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shower

breezer

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