Replacement shower

[davegilsenan]

Hello,
I wonder if someone can tell me what i actually need for the following job.
I have an 8KW elec shower at the moment that needs to be replaced. The feed comes from the consumer unit and has no RCD. The feed is 6mm.
I want to put in an 8.5 or 9.5 kw shower and run a new 10mm cable.
Can an RCD be added to the circuit without replaceing the consumer unit which has re-wireable fuses? Should the pipes in the bathroom be bonded? They're not at the moment. Is the bonding a DIY job? The other work will be done and certified by a sparky.
Any help appreciated. I've has several different electricians telling me I need different things from a simple job to rewire the house!

Thanks,
Dave.

 

[JohnD]

If your consumer unit has rewirable fuses then it is very old, and probably does not have the capacity for a large shower, and connecting an external RCD is not a very neat solution. Is it a Wylex? What colour is it, and is there a "Max load not to exceed" legend next to the main switch?

You would do better to have a new CU with an RCD. Better, get one with an RCBO for the shower, and separate RCBOs for your socket circuits.

It would be best to have this new CU replace your old one for all circuits. If for some reason you don't do that at this time, then don't get a little 2-way Shower CU. Get a big enough one that you can later use for the whole house. The extra cost of a larger plastic box and the fresh air it contains is very small.

 

[davegilsenan]

Thanks John. This job started out as a cheap batroom refurb!!
Anyone have any ideas of cost? Again i'm getting vastly different prices.

 

[JohnD]

You need to get a few local people to quote. Make sure they are covering the same thing. As it involves a circuit to a bathroom, and a new CU, it is subject to Building Regulations. Many qualified Electricians are members of approved self-certification schemes, which means they are authorised to test and certify their own installations; if you use one who is not, you will have to submit papers to your local authority and pay them to inspect it; which in my opinion in more trouble and expense.

Try to get personal recommendations of electricians from friends and neighbours. When phoning, ask if they are members of a self-certification scheme. Write down what you want done, and make sure they are all quoting for the same thing. As you have quite an old installation, they will probably need to update your Main Earth and Supplementary Bonding, so have this included in the price (it is not usually a very bid deal). Try not to specify the brand of CU that you want as they will have their preferences. Some good brands at similar prices are Crabtree, MEM, Wylex and MK. Foreign unbranded ones are available and may not be as sturdy. Some Chinese ones have a poor reputation.

 

[davegilsenan]

Half the problem is I'm not sure what I need....

 

[JohnD]

How about "Install 100A DP main switch & henley blocks to feed existing CU, with new 25mm tails to new 8-way CU with 1x40A RCBO for new shower plus 7 x blanks for future use. Run new 10mm T&E to shower position and connect to electric shower in previous position. Upgrade main earthing to current regs. Provide supplementary bonding in bathroom. Test and issue Installation Certificate"

I am assuming here that either you, or a plumber, will do the non-electrical parts of fitting the shower. If this is done before the electrical work, then you should have the shower working before the electrician leaves

Perhaps some other members can improve this outline?