Workshop socket layout

[Spectric]

One good thing about box trunking is that you can easily use a JB to split a 4mm radial into several legs, make alterations so any connections are not within the trunking and just have flexability. The most important part will be the testing to ensure it is safe, without the tools this is not possible and just because everything works does not mean it is correct or safe.

 

[Spectric]

I will see your twenty four way board and raise you fifty two.

Have used multiple large boards in industrial settings but never seen 52 way in domestic, even in industrial it is common to use multiple smaller boards at level 3 each located closer to the final loads.

 

[MikeJhn]

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.

I would question his qualifications.

Final ring circuits (FRC) as they are now called are only used in the UK, Gibraltar and I think its Hong Kong the rest of the world use Radials, easier to install and fault find, much smaller plugs as no need for a fuse in the plug, FRC's are very old fashioned as are MCB's off RCD's more modern RCBO's available at a reasonable cost now days, in case you don't know an RCBO is a combination of an RCD and MCB so much safer, also means only one circuit goes out and not the whole row protected by the RCD.

 

[MikeJhn]

Have used multiple large boards in industrial settings but never seen 52 way in domestic, even in industrial it is common to use multiple smaller boards at level 3 each located closer to the final loads.

That 52 way is a domestic three phase supply in France, thirteen row is the standard, in Germany its twelve row, but would still be 48 way, off that 52 way board are two additional smaller boards to supply the Kitchen and Workshop off the Kitchen board is another board in the pump house box at the swimming pool.

Very high end domestic in the UK is rapidly going RCBO radial boards, the small domestic CU days are numbered, built in EU boards are becoming the norm.

 

[Spectric]

Testing and looking for faults on a ring can be a nightmare as too many people seem to like taking a DIY approach. An important part of the testing is to ensure it is actually a complete ring by looping out..

Then remove the CPC from the loop leaving the L & N so the circuit is as shown below and now the measured impedance between live and neutral at any socket should be the same, ie X = Y at any socket. None of these issues with a radial because if a line becomes OC then something just fails to work and nothing is left in a potential overload situation.

 

[Katomi woodsmith]

Whoosh right over the top of my head.
If I get to that stage of need. I think I will call an qualified expert.

 

[MikeJhn]

You need to look up "Part P" regulations on what you can do and what you have to notify to Local Building Control.

 

[quintain]

I'm at the stage of laying out my sockets and lighting in my workshop, I plan on running 25mm conduit but cant decide whether to run it horizontally from socket to socket or across the top of the wall and drop down to each double socket. What are everyone's thoughts?

Spacing I thought 12-1500mm between each socket and at minimum of 1200mm from the floor.

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

 

[deema]

There has been a fair bit of discussion about radial on 2.5mm versus ring in 4mm circuits. Both are a safe solution, and both are fully acceptable under the latest wiring standards.

The proposed electrician who has come in for some derogatory remarks may be planning on wiring up a ring main in 4mm, which is a far better solution than either a radial in 4mm or a ring in 2.5mm. It is tolerant of a single earth fault and provides 8mm of conductor for a maximum 32A. The extra cable required really is nominal in the scheme of things. This is the approach I have and do take and also a practice @Sideways has also used.

Comments about testing a ring I just don’t understand. If you disconnect one side of the ring from the distribution board you have a radial circuit. What is the difference for fault finding? Equally which test does a ring cause problems with compared to a radial? I used to make (LEM, HEME where a couple of the brands we used for domestic stuff) test equipment used around the world for everything from power stations down to homes, never came up as an issue otherwise we would have looked at creating an alternative tester to resolve the issue?

 

[MikeJhn]

The standard in the EU is dual pole radials only, carried this over to my UK property, therefore no need to disconnect anything to test or fault find a circuit so much easier and quicker.

 

[Spectric]

Comments about testing a ring I just don’t understand.

The requirements for the test and inspection of a ring main have to confirm that it is infact an intact ring, ie each conductor leaves the board and returns which is a simple test and is done by placing each conductor in series with the other conductors so start with Live and Live return connect to Neutral, the neutral return you connect to the CPC and CPC return is the other end of the loop, now if there is no continuity then one of those conductors is open.

You also have to confirm that the ring has not been bridged, ie a ring within a ring and this is where you only loop the Live & Neutral so you have all the live side impedances in parallel with the neutral impedances and then at every socket the impedance between live and neutral should be the same, if not then something is wrong. You are not just disconnecting one side, you have a total of six wires each should be a loop and not a radial.

I used to make (LEM, HEME where a couple of the brands we used for domestic stuff)

The ones we used were for Dc current measurement, the PR30 and also some larger ones for just Ac and they were like hoover is to a vacuum when it came to current measurement but now they are nolonger grey but Fluke yellow with a price hike to match .

never came up as an issue otherwise we would have looked at creating an alternative tester to resolve the issue?

For electricians it was a routine test, you just did it with a continuity tester and a good low ohm meter, preferably a four wire job which I still have somewhere.

 

[Agent_zed]

It is tolerant of a single earth fault and provides 8mm of conductor for a maximum 32A

I may be missing something but I was under the impression that a 2.5mm ringmain will take 32A? By using 4mm surely you aren't gaining anything as you still can only pull 32A through the MCB. Doesn't that just use more copper and cost more to achieve the same thing.

edit - was thinking this through and realised what you are saying is literally just adding an extra wire from the last 'radial' socket back to the CU to make it a ring. Which I guess makes sense and will depend how far away the last socket is from the CU as to how much additional wire it will use.

 

[Jake]

I may be missing something but I was under the impression that a 2.5mm ringmain will take 32A? By using 4mm surely you aren't gaining anything as you still can only pull 32A through the MCB. Doesn't that just use more copper and cost more to achieve the same thing.

It helps if there is a break (fault) somewhere in the ring. If the ring is complete it does a sort of crude load balancing, but if there's a break it effectively turns into two radials - much of the load could then be on one side of the fault taking power through a single cable only rated for 20A.

 

[deema]

I may be missing something but I was under the impression that a 2.5mm ringmain will take 32A? By using 4mm surely you aren't gaining anything as you still can only pull 32A through the MCB. Doesn't that just use more copper and cost more to achieve the same thing.

edit - was thinking this through and realised what you are saying is literally just adding an extra wire from the last 'radial' socket back to the CU to make it a ring. Which I guess makes sense and will depend how far away the last socket is from the CU as to how much additional wire it will use.

No worries, 2.5mm on its own won’t carry 32A, the ring allows the current to flow in both halves, so effectively you achieve 5mm CSA. For a radial you have to use 4mm CSA which again depending on distance is the minimum thickness of wire that’s required.

From a cost perspective, if you look at Screwfix, a 50m of 4mm twin and earth is £88.90 including the VAT, now, the return will be enough for the vast majority of houses for the two or three rings required, which for absolute safety and piece of mind to me if you rewiring a house is a cost I would happily pay.

 

[deema]

You also have to confirm that the ring has not been bridged, ie a ring within a ring and this is where you only loop the Live & Neutral so you have all the live side impedances in parallel with the neutral impedances and then at every socket the impedance between live and neutral should be the same, if not then something is wrong. You are not just disconnecting one side, you have a total of six wires each should be a loop and not a radial.

Appreciate your insights, it’s a long time ago I was involved with the wiring regs, almost twenty years! Anyway, not sure if it’s a requirement, but I would have thought you had / must test for loops with a radial? There is just as much chance especially with Joe public dabbling with wiring and probably not realising or understanding it’s a radial circuit.

 

[Mel769]

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.

 

[Spectric]

but I would have thought you had / must test for loops with a radial?

There is no loop as such because each conductor L,N & E leaves the board and goes to the first socket with the others just daisy chained and at the final socket there is no return to board unlike the ring. But yes you still have determine the loop impedance of a radial to determine if it is low enough to allow sufficient current to operate the protective device but you no longer measure R1 + R2 as you just plug the tester into a socket and push the test button which gives you the prospective fault current. Yes things seem to change even faster or is it us just slowing down !

 

[deema]

@Spectric thanks for the explanation, I was actually wondering if you have to text for a loop being created with the radial, I have seen this done when they’ve spured off a radial and the at a later date looped the socket back as they wanted to add another socket, all in 2.5.

The other brand we used for domestic stuff was Norma, or LEM Norma after we bought them. They were initially made in Austria until production was moved to the UK. That test equipment was extremely well designed and engineered. The Austrian engineers knew their stuff, they also designed and manufactured primary standard!

 

[DomP]

I seem to have started quite a discussion here, I'll admit I'm well out of my depth as well so I'll make a list of all the tools I might use but as I'll be on my own I can't see how I'll ever use more than a 2000w router and a dust extractor or my festool vac. Jet P/T will be on a 16a supply.