Garage Wiring Advice

[Lee Mason]

Hi all new member here.

First of all im not an electrictian, i have a sparky mate but hes on holiday and i wanted to get advice to get everything setup for his return (im aware of part p regulations etc so wont be doing it all myself).

Anyway just moved house and need some extra sockets in the single garage. Its a detached garage which has a armoured cable connection to the main cu via a mtn 116 hager 16a type b breaker.

In the garage is a little cabtree unit with a 6a breaker for the light, and a 16a type b breaker for the existing double socket.

Thats the existing setup, and this is what i need:

8x double sockets total.

2x above garage door for security lights (connected by fused plugs) and cctv cameras.

2x on each sidewall (1 will be used for another security light, the rest for occasional tool use).

1x external waterproof double socket unit.

Plus the existing double socket on the back wall, which will be used for:
1. an outdoor extension cable used for a fish pond
2. an outdoor extension for a light and thermostat tube heater in a dog kennel.


Being as there is only 1 double socket currently its just 1 cable runing strait to the socket with no return, which correct me if im wrong makes it a radial circuit?


What i want to do is run the cables and fix all the sockets to the walls ready so my mate can just come in and wire it all up to comply with the regs.

Will a 16a radial handle this? and due to the load is there any special wire specs i need to follow or use existing sized cable?

Or should this be converted to a 32a ring circuit? (which i guess would mean new breakers in both cu's and different cable sizes?

As i said above ive already mounted the backboxes and pvc trunking, just wanted to run the right cable and get any breakers if needed ready for when my mates back so he can actually make any connections.

 

[Lee Mason]

interesting, i brought it from b and q a few months ago

 

[DPG]

I'd certainly be using a lower wattage LED fitting. Nearly half a kilowatt of power is going to get that meter spinning!

 

[Spoon]

interesting, i brought it from b and q a few months ago

I just done some searching on Google.
Check out Table 42 (page 84 of 92) on the pdf.
This states a max of 100W.
http://webarchive.nationalarchives....mestic_building_services_compliance_guide.pdf

 

[shaun1]

Wouldn't be a problem adding those to the existing lighting circuit then. It should be a C6 really as fluorescent lights have high inrush current on switching and C has a higher tolerance for that kind of thing than B. Probably worth spending £15 on while doing all the other works.

If changing to a C type breaker, you need to check the Zs of the circuit to make sure disconnection times are still met.

 

[Lee Mason]

Think ill stick to the pir lights on plugs to save any other alterations. Thanks for all the help so far.

On the actual wiring they run all round the garage with the cu in the middle.With the breaker being a 16a with 2.5 twin earth, a ring is just as easy as a radial, so just wondering if theres any limitations of a 16a ring? because havent yet confirmed the feed cable specs, and if thats also 2.5mm i cant make it a 32a ring.

 

[kingeri]

There would be no benefit of running a 16A ring over a 16A radial in your case.

 

[Dan91]

(Its a new built (2015) house and weve just moved in so wanted to put enough in and not have to think about changing anything later on.)


sorry if its been mentioned already but the garage circuit, is it on a 16A mcb in the house consumer unit?

New builds these days seem to just have a 2.5mm t&e go into a whiska box which is then terminated onto a 2.5mm 3 core swa. depending on the garage demand, you might have to upgrade the cable from the consumer unit to the whiska box first.

 

[Lee Mason]

yeah just checked and its on a 16a breaker in the house, and it does appear to be a 2.5mm t&e being fed. not sure about a whiska box as obviously this cable then runs behind the plasterboard.

i thought a 2.5mm was enough for a 16a radial circuit? after seeing the cable i know i cant uprate it to a 32a, which i wasnt intending to do anyway. But are you suggesting the 2.5mm and the 16a wont be enough for a few garage sockets?

 

[Octopus]

^^ it all depends what you plug into said sockets .......

 

[Deleted member 26818]

2.5mm2 T&E can be used with a 20A breaker.
All depends on the installation method.
SWA is rated slightly higher than T&E.
Don’t like the idea of there being two 16A breakers in series, it’s a guessing game as to which would trip in the event of a fault.
As you intend installing extra sockets, and even intend using sockets for lighting, you will need to provide RCD protection.
Easiest method would be to swap the MCBs in the garage for RCBOs.

 

[Lee Mason]

Thanks, so this is what i think im going to get ready.

new 20a breaker in the house cu (maybe an rcbo, my board is full and plan an extension later on, if i replace all breakers for rcbos i can gain 4 slots by removing the dual rcd parts)

new 16a rcbo in the garage (replacing 16a breaker)

new lighting rcbo????? not sure if this is needed.

radial circuit from the garage cu to the plugs.

 

[Lee Mason]

Also i was thinking of wiring the external wall socket into an rcd plug and then into one of the double sockets on the inside. This would reduce the radial circuit by one permanent double, and the external could just be plugged in/turned on when used.

 

[Octopus]

Its best that you get your "mate" involved.....

 

[Deleted member 26818]

If the circuit feeding the garage is already RCD protected in the house by one of the dual slot RCDs, there will be no need for extra RCD protection in the garage.
No need for an RCD plug if the socket you plug into is already RCD protected.

Ideally the circuit feeding the garage should not be RCD protected, though it may have to be as you mention the T&E runs behind plasterboard.