Installing New Shower

[Graham Knox]

Hello to all you friendly helpful people.I am not an electrician but have always done it myself on any job around the house and have not had any problems including electrical work.When i started researching this latest project i kept coming accross people who had simply installed a more powerful shower onto the existing cable.isolator and mcb and were asking why it kept tripping out.I am replacing 6mm cable with 10mm and replacing the 30amp isolator with 45amp.I am also installing a new rcd and mcb.I live in North East Scotland.How much of the installation can i do myself bef

 

[Doc Hudson]

Well Part P is not applicable where you are, I am sure ProDave can confirm if any other obligations apply in Scotland. Otherwise you can do what you want in your own home. However I would always recommend work such as this is properly tested with suitably calibrated test equipment.

Doc H.

 

[Technician]

What power rating on the shower?

 

[ProDave]

Yes we have a lot more freedom up here, no building regulations to prohibit DIY electrical work.

As long as you are competent, and comply with wiring regulations you can just carry on.

Sounds like you are on the right lines with the larger MCB and fitting an RCD.  If there's no RCD on any of the installation at the moment, how about using an rcbo to make it simpler?

What test equipment and testing knowledge do you have to ensure it's all safe?

 

[Graham Knox]

Hi guys,sorry i have taken so long to reply.I have just got in from doing some voluntary driving.Thank's for the advice The shower is a Triton Aspirante Topaz 9.5Kw.I don't have any testing knowledge apart from using a multimeter for checking for continuity and a volt stick.The box i have bought to connect up to mains is a Crabtree starbreaker fitted with a 63amp rccd and a 50amp mcb. is that ok.

 

[Technician]

The manual should give you advice on that.  It should

also tell you to measure the conductor run and give

advice on when it might be too long.  I remember some

of the older shower manuals and they would tell you

when the conductor size had to be increased with the

increase in cable length.

 

[ProDave]

a 9.5KW shower will take about 41A  A 45A mcb would have been better, but the 50A one should be okay.

But what you have is a "mini CU" which is an okay way of fitting a new circuit where there is no capacity on the existing CU or the existing one is not up to current standards.

However, to connect this, you have to tee into the meter tails between the electricity meter and the existing CU.

That requires isolation of the supply, and you need to be sure you know what you are doing.  That is not something the average DIY electrician could undertake, so I hope you are at the very top end of DIY competence to be undertaking that.

A much safer way would be for you to connect the shower, the shower isolation switch and your new mini CU, and then employ a local electrician to come and check the work you have done, and make that connection to the meter tails.  That way all the work you will be doing will be on a dead circuit, and that electrician can test everything properly so you will know it is all safe and correct. 

 

[Graham Knox]

Hi Technician. I have looked at the manual and there is no mention of cable length,however i have laid the 10mm cable the same length as the existing 6mm cable which was for a 7kw shower.It has worked fine with no problems for years,so that should be ok?

 

[Technician]

I think it is a false economy to fit a 6 mm cable when

anyone in the future might fit a larger shower and

thus need a larger cable.  10mm is ok up to 10kW

depending on the run length.  I do not have books

to hand so I could not say what the maximum power

threshold is for this size.

Please take on board what ProDave says because

that is vital.

 

[Graham Knox]

Hi Pro Dave.Yes i intend getting an electrician to do the final installation of the mini cu.This is because i have a main fuse with a wire seal on it.I know i am not allowed to break that seal.If i had meter with a main switch which would isolate the whole house i am competent enough to do the whole job myself.However i will be calling in an electrician.

When i installed the old shower 6mm was recommended for 7Kw if had known then that i would be fitting a 9.5Kw shower later i would have used 10mm and saved myself hasstle now.

 

[SPECIAL LOCATION]

Hi guys,sorry i have taken so long to reply.I have just got in from doing some voluntary driving.Thank's for the advice The shower is a Triton Aspirante Topaz 9.5Kw.I don't have any testing knowledge apart from using a multimeter for checking for continuity and a volt stick.The box i have bought to connect up to mains is a Crabtree starbreaker fitted with a 63amp rccd and a 50amp mcb. is that ok.

Hi Pro Dave.Yes i intend getting an electrician to do the final installation of the mini cu.This is because i have a main fuse with a wire seal on it.I know i am not allowed to break that seal.If i had meter with a main switch which would isolate the whole house i am competent enough to do the whole job myself.However i will be calling in an electrician.

Just a polite note of caution....

without the correct test equipment and knowledge of the appropriate testing you are not competent... 

Thats notwithstanding the fact you have come on here to ask in the first place....

There is a BIG difference from wiring something up and getting it "working"... 

to design, install test and commission in accordance with current wiring regualtions...

Competence and good practical ability or two different things...

you sound like someone with reasonable confidence, ability and the good sense to ask...

But don't fool yourself into thinking you can prove your new circuit is fully electrically complaint with just a multimeter and a voltstick!

Personally I would not recommend any DIY person undertook a new shower installtion...

as they don't have access to something such as one of these..

http://isswww.co.uk/17th-Edition-Testers

Defiantly get it properly tested before energizing anything!!!!!

p.s.

if you were in England this work would need a building regulations compliance certificate via LABC notification... 

 

[Graham Knox]

Hi Trailer Boy.I only mentioned the multimeter and voltstick to illustrate that i know my limitations i will be getting an electrician to do the final connection and testing before energising.Thank you for your comments.

 

[SBS Dave]

Hi Graham,

As ProDave mentioned, the best option is to replace the existing (32A MCB?) with a 50A RCBO.

That way you can isolate the circuit with the CU main switch, allowing you to work safely.

However, you seem to have committed yourself to the mini CU option, for which you definitely need professional input.

I don't know how much the mini CU cost you, but my solution would have cost you £10.00 + postage + VAT.

Either way, the job needs to be properly tested and certified.

SBS Dave

 

[Graham Knox]

Hi David.If i had known that when i started this i would have gone down that road,but as i have bought the mini cu i will just stick with it.Thank you for your input.

 

[SLIPSHOD & SLAPDASH]

Well Part P is not applicable where you are, I am sure ProDave can confirm if any other obligations apply in Scotland. Otherwise YOU CAN DO WHAT YOU WANT IN YOUR OWN HOME. However I would always recommend work such as this is properly tested with suitably calibrated test equipment.

Doc H.

That's what Jimmy Saville thought  :innocent

 

[Graham Knox]

Hi guys.Sorry I have taken so long to reply,I have been plumbing in new bath.Electrician coming next week.I hve a new question.After the new shower is connected up i will have 6mm cable doing nothing,can i use it to connect a 250w towel rail? If so what size mcb do i need.

 

[ProDave]

A 250W tower rail  is conventionally done in 2.5mm, but could be done in even smaller cable say 1mm as long as the fuse or mcb is correct for the cable.

The 6mm is way over spec and you will find it hard to terminate in say a switch for the heater.

It's also almost certainly the old red and black colours, whereas now we should be using brown and blue.

The best advice for the old cable is weigh it in at your local scrap merchant.

Or failing that, if you have a decent length of it, sell it on ebay.  There are still people on ebay who buy old coloured cable for whatever reason (which we best not mention) and you will probably get as much, if not sometimes more than current prices for it.

 

[Graham Knox]

Hi Dave.Thank's for your reply.The 6mm cable is still in place where it connected old shower.I was trying to save having to lay new cable for towel rail.I understand that 6mm is not needed for 250w.Just trying to reuse what is already there.

 

[ProDave]

Well yes if you can terminate it into a suitable switch (does not need to be a 45A one like the shower) then there's no reason not to re use it.

The (presumably new) bit of cable from the switch to the towel rail can be smaller cable.  Don't forget to feed it from a suitable mcb.

This towel rail will need rcd protection, so connect it to a second mcb in your new mini CU that's feeding the shower. 6A will be plenty for a 250W heating element.

 

[Graham Knox]

Thank you very much Dave that is what i wanted to hear.I was thinking of using the old shower isolator switch for the towel rail so the 6mm cable will fit ok.Thanks again for your quick reply and thank's to you all for your help,Iappreciate it.