New Sockets and lighting for workshop

[jazzydan58]

I have a Fuse box in my workshop with a 32amp breaker and a 10 amp breaker. The 10amp breaker has a light switch and currently supplies 10 twin flourescent tube lights. The 32 amp breaker supplies one twin socket next to the fuse box. I

I need to add 3 twin sockets on the left side of the building and 3 twin sockets on the right side of the building. Because of the layout of the building its not possible to create a ring main so what would be the best soloution (two seperate breakers one for left and one for right?) What size wire should I be using 2.5mm or 4mm?

I also need to add two twin flourecent lights on the right side of the building seperatly switched from the existing lighting circuit.

 

[JohnD]

I bet you can run a ring if you want to. You just have to return the cable the same way it came.

you can run a 2.5mm ring at 32A; or a 4mm radial at 32A; or a 2.5mm radial at 20A.

 

[jazzydan58]

I didnt think of doing that!

Would routing the cable back along the existing conduit be the "correct" and in theory allowable thing to do?

 

[davy_owen_88]

If you are running 2 radials down each wall, then all you need is a link between the last two sockets to turn it into a ring circuit.

 

[JohnD]

don't put two cables in the same conduit. there are some rather tiresome calculations for bunched cables and the reduced load they can carry due to reduced heat escape. Simpler to have an "in" and an "out" route.

Also, instead of using conduit, try mini-trunking. This has a channel and a snap-on cover so you don't have to pull cable down a tube.

 

[sparkydude]

If the conduit is 20mm and is not broken along its length, ie is a continuous length with approved fittings and inspection covers then why can you not run a ring in it??? No reason at all, if i was you i would install a 20mm plastic conduit along both sides of your workshop and return them to the fuseboard, Wire the circuit in 2.5mm single core cables with a 1.5 earth and you could even add a couple of spurs to the ring main to switch the two lights either side of the garage.

Nick

 

[ColJack]

if you're wiring in singles it needs to be the same size earth..

 

[sparkydude]

since when col jack? what difference does the size of the cpc make to a cable whether its T+e or singles. after all t+e has a reduced sized earth in it . Every sparks i know uses reduced sized cpcs when wiring in singles asit makes it a lot easier to install . I am open to discussions on the merrits of this, and would welcome any link to a definitive guide on the szing of cps when wired in singles.

Nick

 

[ColJack]

table 54G in the regs book..

minimum CSA of corresponding protective conductor..

up to 16mm² is same size as the phase conductor,
16mm² - 35mm² = 16mm²
above 35mm² then half of the phase conductor size...

( asuming same material as the phase conductor.. )

also, in all cables that contain an earth, other than T+E and 3c+E, the earth is the same size as the phase..

T+E and 3C+E are different because the "un-insulated" earth has a different k value for the equation..