workshop electrics

Good thing no one mentioned the need to inform the DNO that a 4 Kw inductive load that is going to be used on a domestic supply.

No doubt the neighbours on the same phase will eventually get the DNO out to trace the source of the voltage dips.
 
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With respect to the cables, from the house consumer unit I'm using a heavy duty dedicated outside cable which I believe is 4mm
That sounds too small to be honest.

Regarding the comments on the welder, does it really need a 32A connection? My 150A welder plugs into a normal 13A socket, and it doesn't trip the B20 that currently supplies the garage sockets.

I've done this sort of thing twice, but each time I got an electrician to install a CU in the workshop and make the connection back to the supply at the house. He supplied the SWA, I did the excavation and cable routing, to his pre-agreed standards. I could then run the final circuits at my leisure. But this is Scotland so my legal requirements may differ from yours.

I hear your comments about maths, but there do need to be some calculations to make sure the installation is safe, even if these are broad-brush using a worst case assumption because you can't fully quantify all the loads. How else can you size the cable and the breaker at the supply end.

Regarding the legal side, people are talking about Building Regulations, which is not the same as planning permission.

Tony S
 
As a slight aside

An aquaintance had been using a table saw for many years in the garage on a bodged up supply, ( 2.5 mm² twin and earth buried in rubber tubing ).

When that supply failed a fully compliant supply was installed using Henleys on the meter tails and a switch fuse feeding the garage via SWA ( 10mm² or larger ). The saw spun up to speed much faster, the lamps in the house dipped when the saw was spinning up. So far the neighbours have not complained as the saw is used during the day and they may not have noticed the voltage dips.

The inrush current of the saw and the consequential voltage dips in the house ( and neighbours ) was limited by the resistance of the in-adequate 2.5mm² supply cable.
 
What size and type of motor?

As a further aside, when we were fed from overhead 240V we used to get a noticeable dimming of lights when the kettle and toaster were in use at the same time, dropping the voltage below 200V. This stopped after the DNO carried out what they called "reinforcements" in the area.
 
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It all hinges on the welding set. I gave commercial currents expected but much depends on your equipment an old Oxford oil cooled welding set which personally I think should be banned will require a very different supply to a modern switch mode welding inverter and I have seen as yet no details of the welding set requirements.

The 13A fuse will give far more than 13A for a very short time and it is not unknown for the B32 MCB to trip before a fuse blows.

But you have now said you intend to use 4mm² cable you can as easy as me look up the details of a BS6724 SWA/LSZH Cable IEC60502 600/1000V which will show you can use a B32 MCB also this gives PVC SWA cables it's not rocket science but neither is it guess work.

You also say your going to use a TT installation which means you will need meters. Although you should use a special meter for installing an earth rod with two probes which have to be set at a set distance from the rod to measure it quite a complex undertaking there is another way using a loop impedance meter and comparing to the boards earth when you already have a supply. There are cheap plug in socket testers with a loop test however not sure if the LABC would accept those readings?

Most electricians working on domestic are scheme members so don't need to be directly involved with the LABC. I have done about 4 jobs with Flintshire, Cheshire and Liverpool councils involved and they were very different. Liverpool was easy but Flintshire were very careful and they would not allow my son to test in spite of running his own business at the time and having passed his C&G2391 they did allow me to test because I had a degree in Electrical & Electronic engineering which really was wrong of them. I also had a C&G2391 but they did not know that.

The application has to be made before you start and once made they are responsible for site safety.

In the old days of fuses if one made a small mistake it could mean the difference between 0.4 seconds and 0.5 seconds disconnection time but with MCB's it means a difference of 0.01 seconds and 20 seconds so today measuring the loop impedance is very important. Hence why you are required to submit the Electrical Installation Certificate to the LABC.

It would seem your still living in the 1960's and you do need to learn about requirements today not those of a bygone age. It is no good getting upset with those who are trying to help you need to upgrade your skills to modern day.

As to timber buildings that is also incorrect This page does give some guidance and phrases like "constructed from substantially non-combustible materials" would seem to point to opposite where position of wood buildings are limited.

I think you have a lot of reading to do?
 
It seems that you're trying to fill the gap in your experience with arrogance.

You quite clearly don't know what you don't know

If you did indeed, as you say, wire up houses 20 years ago then they're probably as dangerous as your new workshop will likely be.

It's not batteries and bulbs you know, mains electricity is dangerous and kills people like you - who think they know it all, when actually they know very little.
 
It is obvious the OP is not prepared to take on informed knowledge and the mathematical side is a bit baffling to them with regards to a safe functioning design.
I doubt their intention is to install with any regards to safety or compliance or either have the system commissioned legally.
In my opinion the OP has had too much gluhwein over the festive period and needs a head shake!
There is no point continuing to help people out like this!
 
Design? Design what exactly? An electrical system? LMAO!!! Yeah, there's a real lot of "design" going into ensuring there's a series of sockets available near to work benches.

And of course there's a hell of a lot of "design" in ensuring that light is cast where it's needed eh? Don't talk such utter rubbish please, there is no design in this, it's called common sense. Do I need a socket where I'm going to be welding? Yes - Install one!

Do I need good lighting where I'm going to be welding? Yes - Install one!

Do I need a socket/light where I'm going to be sanding, drilling, cutting, routing? Yes - Install one.
Sorry, but not only do you keep proving that you lack the knowledge to do this job safely, you also demonstrate that you do not have the right attitude. I'm not a professional trying to protect my trade (see my sig), but I can see someone like the previous owner of my parents house - which was a BIY nightmare when they bought it with dangerous electrics and dodgy pluming all over.

Yes, each circuit must be designed - not just thrown in. While it may well seem like most installations are just thrown in with no design, in part that's because the spark will have done designs before (and covered 'standard' arrangements during training) so that he knows that certain arrangements will work without doing an individual design on them. Once outside those 'standard' arrangements, then the sparky will need to do a little more work.
When I had an EICR done in my flat, the quite experienced sparky told me he'd need to double check something - and went off home and checked his books to verify whether the submain fuse needed changing given the length of the cable (it did).

IMO, your proposal won't work - either satisfactorily or at all. Fire up a big (or even medium) welder on that and there's a good chance of just blowing the fuse - at the house end which will plunge you into darkness, which means your installation couldn't really be considered to meet the general requirements that the installation be suitable and safe for it's intended use. We used to have a large box of 13A fuses collected over the years - they went down quite quickly with the welder before dad put a 16A socket on the ring (protected by a C16 MCB, and it's roughly in the middle of the ring so unlikely to cause overloading of either cable).

But you also need to consider loop impedance. Don't know what that is ? Then you aren't competent to design an installation. it will be significant using the materials you've described, and it's possible you might not meet the disconnect times required. Do you have the tools, and know how to use them, to measure actual impedances once it's installed ?

So do you know what the supply impedances are (both Zs and Ze) ? Have you worked out the loop impedances of your proposed circuits (both R1+R2 and R1+RN) ? When you add them up, do you achieve values that are low enough to guarantee timely operation of protective devices ?
When you can honestly answer YES to every single one of these questions, then, and only then, could you be considered to have designed the installation to be safe. You won't be able to - you've demonstrated by your posts that you don't know and don't care.
 
It does not matter if workshop is in open air it takes power from the domestic premises so it is notifiable work in England and Wales.

Working on biggest item 150A welder output voltage approx 25v plus 1 volt for every 25A so 31 volt total so no losses 31 x 150 = 4.65kW = 20.22 Amp so 25A is the lowest supply you could possibly use. Likely you will need a C25 MCB for welder so will need a loop impedance of 0.92Ω and a B32 will trip before a C25 so will need a B50 supply for the C25 to trip first.

It's simple maths and if you have the skill to design you will have to do the maths yourself you can't expect others to do it for you.

150 amp Arc welder should run fine on a 13 amp plug for most work, a 16 amp socket B16 breaker is fine for my 180 amp arc welder.
some cheep Chinese welders do blow fuses/breakers for fun though


The OP seems keen to tell us about this "purpose built" "Professional" work shop but the wiring he is proposing seems to be anything but professional,
When I built my workshop (from below ground up) the electrical system was probably one of the most expensive parts of the build along with the door and roof trusses, even though I installed it all myself.
Surely if you want a professional work shop you need a professional wiring system?

Also what's the talk of surge protected extension strips for running heavy tools and equipment, seems like an immediate fire hazard to me :eek:

The only things that need to be surge protected are sensitive electronics like TVs and computers not table saws and welders
 

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