shower connection

verdigris · 18 Jan 2005

I want to fit an electric shower.I have bought a Hagar 8 way CU to replace Wylex CU in my garage (where the power comes in)
I got some MCBs and a RCBO 6-50A for the shower. The CU came with a 100A double switch at the end of the bussbar. Is this ok or should this also be a trip type switch.
What size of wire is now used for the earth connection.

securespark · 18 Jan 2005

There are many things we need to know before we can give you a full answer.

How big in kW is your new shower?

The earth conductor size will be dictated by the cable you choose for that size of shower.

You need to make sure that you have main bonding attached to the gas, water and any other incoming services (oil?) and things like ventilation/heating ducting or exposed girders etc...

Also, you need to make sure that supplementary bonding in the shower/bathroom is up to scratch, where you link things like metallic pipes, objects (bath?) and the cpc's of circuits within the bathroom (like shower shaver point light fitting etc) together to try and make any exposed metalwork at the same potential.

You will need to get the DNO (Co responsible for your meter) to check that your meter and main fuse are up to scratch too. While they are there, you may as well have an isolating switch fitted (or if they don't fit them, you can supply and fit one, and it can be wired in when the come) so that you can isolate the supply (including your CU tails) to change the CU safely without having to bother calling them back.

These things and more need to be thought about in advance.

verdigris · 19 Jan 2005

securespark Thanks for your reply I am having to do this because we are getting a Combi boiler which B.gas thinks will not support a shower.
Any views on this? Water pressure seems to be the critical factor.
Re your answer. I thought of fitting a 9.5 kw shower as everybody seems to be going this way. Is this just another fad or does it really make a difference.
The Elec Board fuse is 100Amps but, thanks to you, I note the meter is only 40Amps. This house used to have storage heaters and I had assumed everything would be able to cope with a shower. Looks as though they down-sized the meter at some point
I thought 10mm cable would be the correct choice for the shower .The run is about 12 to 13 metres.
The new boiler is immediately above the bathroom and I notice the plumber has been instructed to bond all pipes there. These are the same pipes that will feed the bathroom and I have asked that he provides the pipe for the shower.
What do I do about the meter? I reckon the shower will almost take this.
If I say I am having a shower fitted will they upgrade the meter ?
Sorry about the essay. Must go for a Horlicks now.

securespark · 20 Jan 2005

Some combi's support themostatic mixers - double check with British Gas.

Is your pressure not good? What is the flow rate in l/m?

Showers are getting more powerful - 8.5 seems to be the min these days, although you can still buy 7.5.

I'd say as a rule of thumb that any shower 8.5 or over should be wired in 10. Plus, if you ever replace it in the future, the cable (hopefully!) will be Ok for the next one.

Are there any runs in insulated lofts voids or walls? Is the cable grouped with others for any distance?

As for the meter, I told my DNO (Powergen ex Norweb) that I was upgrading my shower, and as I already had three rings, a double electric oven, I really should have a new meter. I got one. Plus, the DNO has a duty to replace meters once more than (is it?) 20 years old. Maybe someone else can help on this detail.

They should replace the meter if you tell them it is only rated at 40A, less than the rating of the shower you want to install, let alone anything else!

Enjoy your Horlicks!!!!

verdigris · 21 Jan 2005

Yes, will speak to him tomorrow. Recently gave my son a thermostatic mixer. had it for ages and not used it. Sod's law.
Just checked my water flow. I reckon its about 17 litres/ min.
Boiler man coming on 1st of Feb. I think I will wait and see how it goes.
There is an old shower installed now. Don't know if its thermostatic.
Has a large graduated control for increasing the temperature but would perhaps prove whether we need to go electric.
Meter is by Ferranti. Property of NORWEB and has a sticker on it
Cert L
7
00

Not really thought this out very well have I. Just moved here, house needs a lot doing to it so its a case of jumping from job to job.

It has two CUs just to make it even more complicated.
One in the garage that used to feed storage heaters and one in the kitchen that feeds the house. Can I use the ex-storage heater points for extra power sockets in the house? What would the DNO(?)
make of that ?
I need more than Horlicks.

mapj1 · 21 Jan 2005

The DNO answer would be 'dunno' - it always is!!
Seriously it is common to convert Storage heater points to sockets, but you'd need the metering changing over too, otherwise these sockets will only be on in the middle of the night at cheap rate

.

There is a risk of them being on a second phase - how many service fuses are there. If so note there is 400v between the two lives

, and ideally sockets on one phase should not be close to the other. In the old regs a segregation of socket outlets of 6 feet or less ('full arms reach') required a 'danger 415V' label, but that is no longer needed. However, mixing phases in the same area, and certainly in the same 2 way light switch for example, is not recommended (not saying you would, more saying please don't!).
Otherwise no reason not to re-use the cabling at least if it is in good order.
rgds M.

plugwash · 21 Jan 2005

verdigris said:
Can I use the ex-storage heater points for extra power sockets in the house? What would the DNO(?)
make of that ?
I need more than Horlicks.

that depends

most likely (if it hasn't been done already) the ex storage heater CU will need to be moved onto the main non-timed supply (or the cuircuits moved out of it but given your CUs are in different locations this may not be easy)

how hard this change is to make depends somewhat on your existing metering arangement but it will obviously require pulling the service fuse which is not something we generally reccomend diyers to do.

how many meters do you have? how many dials does each meter have? if you have more than one meter how close together are they?

as always photos would be helpfull.

verdigris · 22 Jan 2005

Thanks for all your comments, a great help.

I think the meter was changed when the heaters went.
There is only one incoming phase to the single dial meter which is right next to the ex-heater CU.
The tails go to two Blocks, then to a switch with a very large cable through the next room, which may have been a carport at one time, to the kitchen CU.
It would be a major job to put all the ex-heater cables into the kitchen CU, which I suppose is where they really should be.

We just had a fifteen hour power cut and they said we would be off overnight so I took the opportunity and connected the ex-heater CU tails
to the blocks by the meter. It really was a case of an ill wind blowing someone some good.
I t does mean that sockets in the same room will be from the same phase but could be from different CUs.

I have abandoned the shower project until I see if the new combi-boiler will support a shower.
They allowed me to swap the kit I had bought for the shower for boxes and sockets.
Still don't know what a DNO is.

securespark · 22 Jan 2005

Distribution Network Operator.

If you are in the NW like me, then it will either be Norweb (or whatever they call themselves now!) or Manweb.

plugwash · 22 Jan 2005

verdigris said:
We just had a fifteen hour power cut and they said we would be off overnight so I took the opportunity and connected the ex-heater CU tails
to the blocks by the meter.

well you have done it now but i really wouldn't reccomend relying on a power cut for isolation.

ban-all-sheds · 22 Jan 2005

verdigris said:
We just had a fifteen hour power cut and they said we would be off overnight so I took the opportunity and connected the ex-heater CU tails.

Jeez - you were lucky. What if that 15hrs had been a worst-case estimate given out to set expectations so that:

a) They forestall complaints
b) When they fix it quicker every one is pleased.

Don't ever do that again...

verdigris · 23 Jan 2005

OK I get the message. We had trees down and they said they could not climb poles in the dark which seemed sensible. And I did take all precautions.

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shower connection

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