Concern over in-laws wiring

[Tonester]

My father-in-law has asked me to install the electrics for his new shower. I have an electrical background (degree in electrical and electronic engineering) so I understand the theory, but welcome your advice.

On inspection of his setup the existing 7kW shower ran off a 30A separate consumer unit. His new shower (bought without getting any advice) is a 10.5kW Mira unit.

I have ordered him 10mm cable and a 63A 30mA RCD and a 50A MCB in a separate CU.

Firstly his main fuse is labelled 60A - will this be a problem - its a small 3 bed house - with a 30A ring and 2 5A lighting circuits?

When we gutted the bathroom and removed the shower I took out the old separate shower CU. I noticed that the earth block in the main CU was only connected to the shower CU by a thin (only 2.5mm or so) BLACK cable with another length joined to this trailing out of the fuse cupboard, cut where it left the cupboard- presumably from when their hall was decorated.
Potentially the whole house electrics has not been earthed since they decorated the hall!

In shock at this I have connected a 10mm earth cable in its place to a 10mm cable that is visible beneath the service connector block. Is this a legal way to connect the earth, or is there a connection I can make from the block itself? How should I connect this solder or cable clamp?

Thanks in advance of your advice.

Tony.

 

[ban-all-sheds]

You should use an earth block like these:

Which (for TN-S and TN-C-S installations) should be connected with 16mm² cables to the supply earth and the earth bar(s) in the CU(s), and 10mm² cables to the incoming service pipes (gas, water) if they are metal.

I think you should also get an electrician in to check the whole installation out....

 

[plugwash]

if you have more than one CU you really need an 8 way earth block

this way you have a terminal for each CU a terminal for main equipotential bond to the water a terminal for main equipotential bond to the gas and a terminal for the main earth

 

[securespark]

And yes, the main fuse at 60A is woefully inadequate. The supply should be uprated to 100A, and if the CU that supplies the rest of the house is to supply the shower too, then this should be rated at 100A as well.

Call the Regional Electricity Company to upgrade - tell them you have a 60A main fuse and that you want to install a high powered shower. Check the meter too - many are rated at 40A.

 

[ZenStalinist]

Hmm... Most people I know with 60amp supplies have no problems running electric showers. I would say a 60 amp supply can handle either an electric oven and hob, or a shower, but not both. It seems to be when there are two high wattage devices, that the problem over going over the rated supply occurs. That said, if the meter is rated at a pathetic 40 amps... get it uprated!

This place has a 60 amp supply fuse, and the meter is rated at 80 amps.

 

[securespark]

THE FOLLOWING IS A JOKE:

You could always sit back and do nothing and wait for the in-laws to do away with themselves on a bad electrical installation, then pocket the inheritance.........

 

[ban-all-sheds]

Yup - it would come in handy to pay the lawyers defending you when you're up in court because you worked on their electrics...

 

[Tonester]

Thanks for your help everyone. I'll put in the 16mm cable to a block, wire in the shower and get a qualified electrician to come and check it over before go-live. Better to be safe than sorry, despite the jokes about inheritance!

Earthing's my main worry with a shower of this size especially if I fit an RCD - I'd like it to work.... I guess the other thing to check is earth bonding on all the plumbing etc.... oh joy

Also the house has a 100A meter but the main supply block although 100A on the casing has a sticker saying 60A.

cheers,

Tony