Workshop socket layout

[Spectric]

One question, why do people say to go for a radial circuit? My electrician says ring all the way.

I would put your electrician out to graze, he must be an outdated dinosaur or maybe a domestic installer !!

Look up the history of the ring main, it came about due to a copper shortage and not for being the better solution. Quote

" Ring final circuits originated in the UK, for historic reasons dating back to 1942 and the reconstruction effort following World War Two.

The Post-War Building Studies Committee No.11 was convened by the Council of the Institution of Electrical Engineers in June 1942. It was tasked with making recommendations to facilitate the building of the one million houses predicted to be required in the aftermath of the war.

In the face of shortages of materials, ring final circuits were conceived, to minimize the amount of copper required. The 13 A socket-outlet with fused plug top to protect appliance flexes was also introduced at this time. It was said that the ring final circuit typically required 30% less copper and could save up to 25% in cost. This allowed 15 A sockets to be installed in all rooms cost-effectively. "

A radial runs from the board through each socket and then stops, no return back to the board. A ring on 2.5mm cable and a 32 amp protective device is only safe when the ring is unbroken, if there is a break then the 2.5mm cable is insufficient for the current needed to cause the protective device to function.

 

[DomP]

He's certainly no dinosaur, mid 30s and heads a team at a modular building company.

What I don't understand is that all houses use ring mains, wouldn't a ring use more cable than a radial as it has to return to the cu.

 

[Phil Pascoe]

No, two radials would be much the same length as the ring but using heavier copper.

 

[Mel769]

If you opt for 4mm radials; then you will not fit x3 4mm cables into the back of a socket. This is all good until if you decide in the future to run a spur (additional socket) from one of your original sockets. ! You Might get away with a 2.5mm radials if the length is not excessive and depending on mcb size. Sometimes it's easier to run a 32a ring in 2.5mm for the above reasons and to keep costs down; but its doable to have radials certainly.

 

[Spectric]

What I don't understand is that all houses use ring mains

They did once upon a time when we would use a ring upstairs, a ring downstairs and put the kitchen on it's own ring but with a radial for the cooker on 6mm.

Today it is very different with appliances needing their own 16 / 20 amp radials such as many european ovens and who would have though 24 way boards would be used in domestic.

If you opt for 4mm radials; then you will not fit 3 into the back of a socket.

This is where design comes into play, you can run 4mm to give a 32 amp radial and with a 32 protective device or a 2.5 radial from a 20 amp protective device and when you think that you are fitting 13 amp sockets where only a certain percentage of them will ever be in use at the same time then look at your loads. With a radial you have one in and one out, why the three ? With correct design you can avoid any spurs but in the event you want three 4mm then it is easily done using the right fronts.

https://www.cef.co.uk/catalogue/pro...witched-socket-with-screwless-terminals-white

 

[Mel769]

This is where design comes into play, you can run 4mm to give a 32 amp radial and with a 32 protective device or a 2.5 radial from a 20 amp protective device and when you think that you are fitting 13 amp sockets where only a certain percentage of them will ever be in use at the same time then look at your loads. With a radial you have one in and one out, why the three ? With correct design you can avoid any spurs but in the event you want three 4mm then it is easily done using the right fronts.

Yes design it now and not add anything in the future; but it's still not a bad idea to future proof. There are some (not all) sockets available that will accept x3 4mm cables, but bear in mind it can be a pain getting x3 4mm's all buttoned up in the back of a socket box and then get the front screwed on. Just saying; personally I would go for a ring for general sockets in a workshop and maybe 1 or 2 dedicated radials for any large equipment. My workshop is run form a 13a spur in my kitchen; never had an issue - that feeds 2 lights and x3 double sockets for general power tools.

 

[Phil Pascoe]

My workshop is run from a 13a spur in my kitchen; never had an issue - that feeds 2 lights and x3 double sockets for general power tools ..........................

Yeah, that complies with all the regs. doesn't it?

 

[Mel769]

Yeah, that complies with all the regs. doesn't it?

Yep sure does, all it is is a glorified extension lead with swa wiring

 

[Phil Pascoe]

As a spur???

 

[deema]

I’ve just finished wiring up a new workshop, I’ve gone from plastic trunking around the top of the walls with drops 20cm down to either an interlocked outlet or metal clad double sockets. The plastic trunking unlike metal trunking needs fire rated metal straps every meter to support the cables should there be a fire. The cost of metal / plastic trunking is about the same.

In my last workshop I ran the wiring around the walls at I think 1.2m, it was always in the way / stopped best use of the walls.

 

[Sideways]

I've mentioned before that I'm not quite so precious as @Spectric over the use of rings. I have one ring around the top of my garage walls looping down to twin metalclad sockets. My ring is wired in 4mm singles so it is substantially over specified to deliver 30 Amps and this overcomes the major defect of ring mains.
In a couple of places I have a block of two double sockets (so 4 off 3 pin sockets in total) installed together. The lower twin is wired as a very short spur off the twin outlet above it. This is handy to avoid multiway adapters when you may need a battery charger or two, and a couple of plugtop power supplies for LED lights or phone charging all in the same place.

I have no particular issue fitting 3off 4mm singles into the back of a bog standard screwfix metalclad outlet.

In a small space where everything is visible, I find the topology of a ring around the garage feeding all the 13A outlets perfectly effective.
I have radial circuits in there too to feed the larger machines and 16A sockets where I need them.

Also. Search for some of the threads about wireless remote switched outlets here in UKW. A switch you can operate from a keyfob in your pocket is super useful for turning on and off a shop vacuum.