View Full Version : Any qualified electricians here?

Mad Professor
06-11-2013, 06:29 PM
Good day all.

I am looking for some advice before I start building my new workshop.

As said above I am looking to start building a new workshop at the bottom of my garden soon.
And I am looking for advice with regards to getting power to the new workshop.
I am looking at needing no more then 5kw (22A) of power usage at any one time in the workshop, but it's approx 40m from where the workshop will be to where the houses main Fuse/RCD panel is.
I have been reading about on google, and fully understand that I will need armoured cable.
Looking at online it seems that I will need cable with a core area of 4.0-6.0mm2.
The other thing I have read is regarding the earthing of the new workshop, I find one post saying it's safe to use the earth coming from the house, and other posts saying that the workshop should not be connected to the houses earth, but have it's own earth rods fitted.
I would like to under take all the fitting and wiring, and have a qualified electrician go over it all, and sign it off.
I am also looking at putting the armoured cable inside conduit that way if I need to add any more wires later I can just pull them though.
So can anyone here give me any advice, or a list of web sites to try and find out more details.

Thanks for your time.

Best Regards.

Web Goblin
06-11-2013, 08:30 PM
4mm might do at a push but i would fit 6mm just to be sure. Dont have my regs book handy so cant work it out. Some people will export the earth from the house supply depending on the supply type, I did on mine, but the best way it to TT the external installation by fitting earth rods.
Run in the wire armour from the house supply to the workshop and connect the cpc, external part of the cable, only at the house end. This will protect the cable. Connect the phase conductors at the workshop isolator and insulate the end of the wire armour cpc from any connections. Fit earth rods at the workshop and use as your earth connection.
If you go down this route get an electrician to do this for you as this will have to be installed and tested correctly to ensure that it will work and possibly save your life.


06-11-2013, 09:02 PM
Things change, I'm qualified but not Part P certified and have always worked in industry rather than installations so I can't say anything for certain. If it was for myself I would see if the local library had a copy of the 17th edition Regs and follow the advice in that. I won't say how things used to be done because it won't apply and will just confuse the situation but I think you could install it yourself as per the latest regulations and have a Part P electrician test and sign it off, I also think you have to seek permission or at least inform the local council about the installation.
6mm2 sounds good to me as does running it in a conduit but I don't think you should run cables of different voltages within that conduit.
At the end of the day it's the 17th editon Regs. and any Part P supplements you need to follow.

Also are you proposing 2 core or 3 core cable ?, if you follow the advice of Web Goblin I think he is suggesting 2 core (Live & Neutral) from the house and providing the 3rd earth core locally via rods.
I also agree that if this is the correct route to follow you should not attempt to install earth rods yourself as installation is not just hammering a rod into the ground, at least it never used to be.

06-11-2013, 10:31 PM
Can't see a problem with armoured cable for the power supply,then just install low voltage @ internet ect in a seperate conduit.I have no electrical qualifications but i have been looking into this because i have to do something similar.
If anyone knows the separation distance from power cable to ethernet/telephone line that would be appreciated(power & Ethernet in same trench)

07-11-2013, 06:47 PM
Fit the biggest you can.

Even though what you've got might only draw 22amps, it's always better to allow for future purchases as best you can. If you only fit the bare minimum, the chances are it'll cost you a lot more in the long term.

In the latest TLC catalogue, there's only 27 difference between 50 metres of 4 and 6mm2 two core armoured, and 30 for three core.