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spitfire
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26-05-2020, 01:20 PM
1

Question For Judd

I have just fitted the new electrics to the Office. there is a spur off the Consumer Unit which at present only supplies a double socket in the garage, single weatherproof socket and the Central Heating Boiler. At present I am about to extend the spur to the office which has three double sockets, a weatherproof socket, and interior and exterior light (on 5 amp fused switches). The last double socket is the terminal point for the spur, so the question is this, I can leave the set up as it is or, I can extend the cable on the last socket to an accessible point back inside the Garage and terminate at a suitable Junction Box, so, if at any point i may want to I could change the spur and form a ring, I know the Office will not have equipment drawing many amps but want to be sure.
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26-05-2020, 01:36 PM
2

Re: Question For Judd

I don't want to have to faff at the Consumer Unit, this was newly fitted when I built the Downstairs Loo. what I would do is interrupt the the downstairs ring at the socket nearest the Garage, and leave the spur as is, and incorporate it with that.

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Judd
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26-05-2020, 03:12 PM
3

Re: Question For Judd

To answer your first post. Was this spur taken from the ring-main MCB or on its own 16amp MCB? If it is the latter (assuming a 2.5 mm cable), you can add as many extra sockets as you like but consider the length of the cable to the far socket to account for volt-drop and earthing resistance. Any lighting or appliances can be taken from this cable provided that the lighting/appliance circuits are protected and de-rated by switched fused spurs with the appropriate fuses fitted. Remember too that if the MCB is rated at 16amp, your maximum load should not exceed 3kW (13amps).

A quick calculation tells me:

Assuming cable length at 20 mtrs...

Incoming earth (Ze) - 0.8 Ohms (need to verify type of supply)
Design current - 13amps
MCB - 16amps
Volt Drop - 4.68V (11V max allowed)
Earth at furthest point (Zs) - 1.26 Ohms (Max allowed 2.2Ohms)

If this cable is taken from the ring-main MCB (32amps), then it should be connected via a 13amp fused spur near the Consumer Unit to de-rate the cable.

Your second option of running a further cable back to the consumer unit from the furthest socket is sound and you should consider this if you intend adding more sockets/load to the circuit. If you do decide to do this, the extra ring-main should be on its own MCB and not piggy-backed onto an existing one but looking at the new Consumer Unit, that shouldn't be a problem.
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26-05-2020, 03:17 PM
4

Re: Question For Judd

The first thing that occurs to me is..Have you been panic buying loo rolls Spitty?
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26-05-2020, 05:27 PM
5

Re: Question For Judd

Originally Posted by EZ Rider ->
The first thing that occurs to me is..Have you been panic buying loo rolls Spitty?


EZ, I was too fixated by the poppies and didn’t notice the toilet rolls!
realspeed
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26-05-2020, 05:48 PM
6

Re: Question For Judd

spitfire
So you are aware

Any electrical work you do has to be passed by a qualified electrican and certified before you connect up to the power source. This is for your own safety and actually a legal requirement.
Don't forget the circuit board chart DB1 will need updating by the electrician
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26-05-2020, 06:10 PM
7

Re: Question For Judd

Originally Posted by Artangel ->


EZ, I was too fixated by the poppies and didn’t notice the toilet rolls!
Same here LOL
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26-05-2020, 06:19 PM
8

Re: Question For Judd

Originally Posted by realspeed ->
spitfire
You do realise that any electrical work you do has to be passed by a qualified electrican and certified before you connect up to the power source. This is for your own safety and actually a legal requirement.
Don't forget the circuit board chart DB1 will need updating by the electrician
Not necessarily. Certification only applies to new circuits and replacement consumer units, work in bathrooms, kitchens (unless only replacing damage wiring or sockets), and new supplies to outbuildings or gardens. What Spitfire is proposing are additions to an existing circuit so falls within the remit of a `competent person`. The only caveat to that is if he decides to convert the existing circuit (a spur) into a ring-main which then falls under the new circuit restrictions.

https://www.buildingcontrolpartnersh...rks/intro.aspx
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26-05-2020, 07:21 PM
9

Re: Question For Judd

What about I.E.E regulations?
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26-05-2020, 07:43 PM
10

Re: Question For Judd

Originally Posted by realspeed ->
What about I.E.E regulations?
What about them? As long as Spitty follows the Regulations from a safety point of view then there's no issue.

I think you may be confusing the Regs with the requirements of Part P which are part of the Building Regulations. Anyone classed as competent can do electrical work except for the notifiable work mentioned earlier.

As a spark, I'm obliged to follow all the aspects of the BR except for the insulation (heating), noise transmission and the actual building structure provided that I don't compromise or weaken that structure - that pertains to not drilling too many holes in joists for cable, not cutting big channels out of joists as was the practice back in the day. I have to follow Part B (fire), Part L (conservation of fuel and power- i.e. fitting the appropriate lighting and heating, Part F (ventilation). I can't see Spitty getting too involved with that lot.
 
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