Workshop socket layout

[Mel769]

Theres still variables before selecting the size of cable you need and the fuse size . Your proposed new circuits will rely on the size of supply cable to the workshop), if theres already a supply there then whats its size, type, length of run & existing protective device. If the supply cable is not already installed then where will it be fed from ?. Other variables include does the workshop have metalwork touching the ground (structual or water/gas pipes), will the proposed conduit be hidden behind walls within insulation - these can all have a impact on cable size and other regulations. If you were more local I would be happy to help where I could. Probably best to call a a local electrician in the local paper for an appraisal before you throw any money at it !

 

[Scruples]

Horizontal supply to be at the top and then down to sockets and keep all runs visible. Be prepared to increase the number of sockets & outlets as work and tools require

I preferred a worktop height for my 100mm trunking, running around the workshop. I easily added extra sockets (for convenience rather than load) and I'm still pleased I did it that way after 12 years.

 

[Scruples]

I would put your electrician out to graze, he must be an outdated dinosaur or maybe a domestic installer !!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

In all my days as an electrician I never came across 15A sockets on a ring main in the UK. The 15A sockets/plugs were not fused so that would be a no-no for appliances plugged into it.

I spent my time ripping out radial final sub circuits, in both lead and VIR and replacing them with 2.5mm² TWE PVC/PVC ring mains. To my mind, it's still the best, especially since few people have 3kW fires/heaters as their main heating sources and demand on the ring, these days, is very small. And yes, the ring is cheaper than having many radials.

The only advantage I can see for radials is the ability to feed one room on one radial so that switching off a teenager's music doen't affect the rest of the house.

In my workshop, I have a ring around the walls at dado height and, at the location of the table saw, I wired a 16A BS4343 socket with a 20A DP switch from the ring. The ring is protected by a 16A MCB and a 30mA RCD so everything is well within spec.

 

[Spectric]

In all my days as an electrician I never came across 15A sockets on a ring mian in the UK.

Neither have I but then I am not that old, those plugs had round pins with no earth, but the earth was introduced later

.

I do vaguely remember these though

My nan plugged her iron into one of these back in the mid sixties, note the exposed live pins and metal construction but then many will remember the electric bar fires that had fully exposed live heating elements.

 

[Agent_zed]

One thing that might have been missed is what is your proposed demand ? Once you know how much power you need then you can design around that. My 13a radial is all I need for small power & lighting. Have a small bandsaw and a mitre saw; and two led batten lights, never use any more than 1 power tool at a time but and so I'm not a heavy consumer. Which is good cause I'm into saving the planet a bit more recently. I often dream of having a mega compressor and a few welders thou.

This was my thinking. My house and garage is next to other houses. If i was out in the sticks and had a massive workshop where I could have a massive P/T and huge extractors I could see the need to ensure the wiring could take many kw's.

I don't have the room for huge machinery and neighbours would probably complain if I run anything bigger than I already do.

It's highly unlikely that even if my ring main broke (and I had effectively 2 radial 2.5mm runs) that I would exceed the rating of the cable. Even if I was running my 2kw tablesaw and a 1kw extractor It should still be within 13amps and that's assuming they are both on the same side of a break. That is the biggest I can ever realistically seeing me running at the same time.

As others have mentioned it comes down to spec'ing to what is appropriate for the situation. it's just a waste of resources if everyone overspec's everything by ~100%.

 

[Sideways]

Even if I was running my 2kw tablesaw and a 1kw extractor It should still be within 13amps

These aren't resistive loads like electric heaters or powertools.
They are induction motors.
You can't just add up the kW and use 1kW = 4 Amps.
It doesn't work like that.
Please don't do your own electrics when you don't know enough to do this safely.

 

[Spectric]

Yes Dc and Ac RMS values only compare when there are no reactive impedances such as Inductance / Capacitance loads.

There is a lot more to electrical theory than many realise and Ac circuit analysis is not just ohms law and can get very complex once you have multiphase systems, it is much easier to get things wrong than do the job safe and correctly.

 

[Scruples]

Neither have I but then I am not that old, those plugs had round pins with no earth, but the earth was introduced later

View attachment 194262 .

View attachment 194260
I do vaguely remember these though
View attachment 194261
My nan plugged her iron into one of these back in the mid sixties, note the exposed live pins and metal construction but then many will remember the electric bar fires that had fully exposed live heating elements.

Yes,
In my childhood I saw and used 15A plugs and s

These aren't resistive loads like electric heaters or powertools.
They are induction motors.
You can't just add up the kW and use 1kW = 4 Amps.
It doesn't work like that.
Please don't do your own electrics when you don't know enough to do this safely.

Some power tools aren't always purely resistive if they have AC motors or transformers.
But, let's be honest, most single machines, with motors will run at a PF of 0.8 which won't alter the demand significantly.
Three phase machines will use less current/phase so the 0.8 PF is also not worth worrying about unless you're in a factory of machines.