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Workshop wiring

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I am fairly sure that what I am doing is acceptable, but no longer have experts to confirm.

I have wired the workshop from a 32A mcb in the house consumer unit with 6mm cable.
This feeds a small consumer unit in the workshop. Via a ECLB there are two 16A and a 6A mcb for lighting.
I am running radials from the 16A mcbs . I plan four or five double sockets from each.

Worst case, there will be a 2kW heater and a table saw running. Obviously not on the same radial.
Plus maybe a battery charger.

Comments??
 
A few questions, off the top of my head:
  • What is the supply cable from the house to the workshop, and where and how is it run? You've said 6mm2, but what type of cable and how long?
  • What is the workshop consumer unit made from? Under current regs it needs to be metal, but there's a lot of 17th edition equipment still around to be bought.
  • I'm assuming the workshop socket circuits are in 2.5mm2 cable - if not, then what is it?
  • By ECLB, do you mean a 30mA RCD?

Apart from that, it comes down to things being installed correctly (including checking the manufacturer's torque specifications for your consumer units) and your test results being in range. Also note that since this involves installing new circuits (both at the house end for the workshop supply, and the three circuits in the workshop itself), this is notifiable work and needs a building control completion certificate. For that you either need a friendly Part P registered electrician willing to certify your work, or to submit a building notice and have the council's inspectors visit.
 
Oh, and as the designer and installer, you should be filling in an electrical installation certificate for it - there are generic model forms in BS7671, or available for download from a variety of sites. That doesn't replace the building regs completion cert, but a properly completed one should help convince the inspector that you know what you're doing.
 
spb":wt5g9lbj said:
A few questions, off the top of my head:
  • What is the supply cable from the house to the workshop, and where and how is it run? You've said 6mm2, but what type of cable and how long?
  • What is the workshop consumer unit made from? Under current regs it needs to be metal, but there's a lot of 17th edition equipment still around to be bought.
  • I'm assuming the workshop socket circuits are in 2.5mm2 cable - if not, then what is it?
  • By ECLB, do you mean a 30mA RCD?

Apart from that, it comes down to things being installed correctly (including checking the manufacturer's torque specifications for your consumer units) and your test results being in range. Also note that since this involves installing new circuits (both at the house end for the workshop supply, and the three circuits in the workshop itself), this is notifiable work and needs a building control completion certificate. For that you either need a friendly Part P registered electrician willing to certify your work, or to submit a building notice and have the council's inspectors visit.
Click to expand...

Cable is normal flat stuff. 10 metres within the house and then 4 meters armour into the workshop ( this is overhead )
Consumer unit is brand new and conforms.
Yes
Yes

Will get it p ed by my sparky as soon as the lockdown is over, this is why I am checking here as I can't ask him as he has enough problems at the moment.

Thanks
 
If the outdoors part of the cable is SWA and the armour is properly earthed, that all sounds fundamentally sensible. A few more things to check, though:

  • Normal 6mm2 twin and earth (i.e. the indoor part of your supply cable) only has a 2.5mm2 earth conductor - that's enough current capacity for the garage CPCs, but check your earth fault loop impedances carefully. The extra resistance of the smaller cable shouldn't be troublesome over 14-odd metres, but better to know sooner than later if you need to change anything.
  • You might need a catenary wire to support the overhead cable - I don't have my copy of the regs to hand at the moment, but from memory I think it's a maximum 3 metres you're allowed to span unsupported.
  • Do you have any metallic water (or gas) pipes coming into the workshop, or any other metal building parts that might connect to ground? If so, you'll either need a 10mm2 earth conductor for the supply cable so that you can bond them properly, or to put in a separate earth rod for the workshop and separate it from the house earthing system. If not, then exporting the house's earthing system (assuming it's TN-C-S, as most modern-ish houses are) will be OK. From your build thread it doesn't look like it, but proper bonding of extraneous-conductive-parts is important enough to be worth checking.

(NB: I'm not a proper electrician, just a DIYer who actually tries to follow the rules and has a copy for that purpose. If your local sparky disagrees with me, listen to him/her instead.)
 
SPB,

Thanks for the feedback, keeps me thinking.

I will need to get the sparky to check this, at moment I am relying on one of those test plugs with neons that show correct wiring. I am aware that they are not perfect, but it’s a bit of assurance.

The length of the armour cable between where its cable clamped to the house wall and the workshop is less than two meters.

Nothing metallic in the workshop.
 
Hi Lurker
It’s definitely worth checking with a qualified sparks, I recently built a pottery studio in a clients garden.
To assist the sparky I did all the cable routing to the studio, it went through the house in the flat type 10mm twin and earth, I took this to their boiler house ( the old outside loo) and then 3 core - 10mm armoured to the studio, the Electrcian who did the connections said he had to install something extra as it wasn’t a continuous run of cable, there was a change in cable type (T&E to armoured ) for the life of me i can’t remember what it was he had to install.
 
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