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irishsailor

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I looking for advice.. Rewiring a garage using SWA from house CU, intend burying the cable IAW with rules. The garage will have a new lighting circuit and either a ring or radial for power.

What size SWA will I require and why??

What is a good choice of CU for garage and why??

When you look at the rating of a CU how does the ring and lighting circuit determine this??

Sorry If these questions seem stupid!!

Cheers
 
S

Spudnik

  • Thread Starter Thread Starter
  • #2
SWA - what sort of distance?

Choice of CU is dependent on budget. (metalclad Hager if not an issue.)

A four way metalclad CU may have a 63A main switch but some have 100A. Not really an issue for garage power to be honest. The reason a metalclad cu is better is because it is rigid so makes terminating the SWA easier.

There are a fair few other things that also need to be considered before anything is installed in the garage, ie distance from CU, type of earthing a the house, RCD protection services in garage, main bonding etc etc.

These questions i wouldn't call stupid, but they are fairly basic and one asks if you are up to the job?

This type of work is under Part P of the building regs and is therefore notifiable.
 
M

maddfridge

  • Thread Starter Thread Starter
  • #3
I looking for advice.. Rewiring a garage using SWA from house CU, intend burying the cable IAW with rules. The garage will have a new lighting circuit and either a ring or radial for power.

What size SWA will I require and why??

What is a good choice of CU for garage and why??

When you look at the rating of a CU how does the ring and lighting circuit determine this??

Sorry If these questions seem stupid!!

Cheers

hi there

no question is stupid !!

a metal clad board is a good idea but burying cables etc derates the sizes etc again without info not easy. there is no reason not to use the armoured shaeth for earth butb a lot of people do pull in and extra earth wire .

The main reason for this is largeresizes do not have the capacity to allow the sheath for earth in the csa available. a 1.5 swa can carry up22 amps or so but try table 4d4a onwards for the sizesof current etc. a 25mm armoured buried in the ground can carry 99 amps ref method col no 9

You need to work out your load and follow the cable sizing in the regs etc see scaddens books they are good to start with . ie 17th edition i think it is in there

good luck

cheers
 
If its a detached garage,I would think it would be outside the equipotential zone(is that term still used?)What I would probably do is use 4mm swa and terminate it in a
galvanised thru box adjacent to your consumer unit.You could probably get away with using an insulated inclosure.I would ensure that the armour is connected to
earth at the house end only.Then you could convert your supply arrangement to TT.
AND install an earth electrode going to met in garage.You should also not forget
to install 10mm earth to any copper pipework in garage,eg boiler.Your consumer
unit in the garage could then be fitted with a 30ma main swith with a 6a mcb for lights and 32amp for ring or 20/16amp for radial.
 

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