Shower installation

[fickle]

I am installing a 9.5Kw shower.

Can I use 6mm cable with a 40 amp fuse?

My memera 2000 CU doesn't have an RCD. I only have 1 slot left for the fuse and I can't find a 40 amp RCBO for the memera 2000. Do they actually exsist?

 

[Taylortwocities]

Before you do anything else.

1. Use Ohms law and work out how many amps 9.5KW is.
then
2. Go to www.competentperson.co.uk and get someone who knows what they are doing.

 

[fickle]

I have used ohms law and 9.5Kw / 240v = 39.5amps
Which is why I choose a 40 amp MCB

If I am wrong can you please explain why.

Also do Memera make a 1 slot 40 amp RCBO?

 

[securespark]

You've used the incorrect voltage in your calculation.

 

[fickle]

You've used the incorrect voltage in your calculation.

OK so should it be 9.5kw/250v = 38 Amps.

A 40 Amp fuse should still be OK, or am I still going wrong?

 

[Taylortwocities]

I'm not sure you should be doing this work.

The standard voltage is 230V. Do the maths again and you will find you probably will need 10mm cable and a 45A breaker. Will depend on the installation method etc etc.

You can buy a Pod from MEM and convert the CB to an RCBO.

 

[djaa]

Fickle a bathroom is a special location and thus it is advised that you consult BS7671 17th edition, you need to consider many things for correct cable size, if only it was one calculation required life would be a lot easier for us electricians. your supply system is a start do u have TT or TN-S or TN-CS, this will determine your earth loop impedence for this circuit. If that has confused you add a few more consideration, voltage drop, method of installation, etc etc. To top all this off testing of the circuit to ensure all users have a safe and a long life.
Please if in any doubt call a professional.
UK supply is now 230v or 400v 3 phase.

 

[ban-all-sheds]

Secure and TTC - how do you know what the rating of his shower is at 230V?

 

[Spark123]

I think you'll find shower manufacturers still state the rating at 240v - maybe because a 9.5kw (240v) shower sounds better than the same unit 8.8kw (230v).
Only way to find out for sure is to look in the instruction book / consult the manufacturer.

 

[Taylortwocities]

We don't, and he certainly doesnt.

Got to raise a big red flag on this one. It could be 207v, it could be 253v. But the nominal voltage is 230, lets start from there.

Nobody's mentioned this yet.... //www.diynot.com/wiki/electrics:part_p:diy_electrical_work_and_the_law

Oh heck, there I go again. I only stutter when I say P

 

[ban-all-sheds]

The point is that if all you've got is the 240V rating then you have to use 240V in your calculations.

 

[fickle]

Ok I have decided to use a 40/45 Amp MCB like it says in the booklet with 10mm cable. I will have to get a new consumer unit with RCD as I can't find a 45 AMP RCBO for my Memera CU.

More questions

1. Does the shower have to earthed independantly other than the earth going back to the CU in the twin and earth cable?

2. Can the cable be ran in trunking on the outside wall of my house?

 

[Cremeegg]

I almost wonder why I am bothering as you have made it very clear that you are not reading what good advice you've been given.

MCB's are either 40A or 45A not 40/45A. Get someone from competent person website in to do the calculations for you as it's clear you are not understanding what good advice is being given to you. A competent person would also be able to do the correct calculations for you to see if running a cable in conduit would be acceptable.

A cable would run (present tense) in conduit not ran (past tense).

 

[ban-all-sheds]

More questions

1. Does the shower have to earthed independantly other than the earth going back to the CU in the twin and earth cable?

2. Can the cable be ran in trunking on the outside wall of my house?

When do you plan to submit your application for Building Regulations approval, and what do you expect to be putting down as the way you'll be ensuring compliance with P1?

 

[flameport]

I will have to get a new consumer unit with RCD as I can't find a 45 AMP RCBO for my Memera CU.

You do not need a new consumer unit.

You can't find a Memera 2000 45A RCBO as they do not exist.
40A and 50A types are available.
Which one is suitable for this installation will primarily depend on the actual rating of this shower, the cable you are intending to use, how the cable is installed and how long the cable is.
It is also possible that neither of them are suitable.