New electrics in old garage

[Nick M]

Hi,

I'm converting an old 1970's garage on a budget into a workshop/storage space and have nearly finished lining the concrete panels with stud work.

Next on my list of things to do is put in some electrics, but I have some questions...

I plan on getting the garage power connected to the house (about 15m away). An initial quote was in the order of £1k which was enough to put me off doing it this year.

So for now, I'm planning to run an extension lead up the garden to power the circuit. I'd like to do things as close to regs as I can so that it doesn't all need re-doing when I have the cash to have it hooked up properly.

I'll be putting in a consumer unit, a lighting spur (single switch to two waterproof 2 x 58w strip lights), and a ring for wall sockets.

- Is the lighting spur ok, or does it need to be a ring?

- Is 1.5mm^2 enough for the lighting spur? I think at 240W it's more than enough, but it will be on a 6A MCB..?

- Is 2.5mm^2 ok for the socket ring? It'll be on a 16A MCB, but I may want to increase that to 32A in the future

- Do I need to put cables into conduit if they're going in/on/behind stud work? Or can I just clip them to the stud work?

- I'd like a light switch by the external door - are there any regs about how close to the door opening the switch can be?

- When I'm connecting cables up to the consumer unit do I need to worry about the IP66 rating (it won't been near the external door)? I'm guessing yes, just because of sawdust, etc?

- When fitting cable glands for the consumer unit, is it one cable per gland, or can I put several into the same gland?

Many thanks!

Nick

 

[flameport]

- Is the lighting spur ok, or does it need to be a ring?

Lighting circuits are radials.

- Is 1.5mm^2 enough for the lighting spur? I think at 240W it's more than enough, but it will be on a 6A MCB..?

Grossly oversized, 1.0mm would be the usual choice.

- Is 2.5mm^2 ok for the socket ring? It'll be on a 16A MCB, but I may want to increase that to 32A in the future

16A rings are not defined. 2.5mm would be ok for a 16A circuit in most situations, and would normally be used for a 32A ring.

- Do I need to put cables into conduit if they're going in/on/behind stud work? Or can I just clip them to the stud work?
- I'd like a light switch by the external door - are there any regs about how close to the door opening the switch can be?

No, provided they are in the correct zones. They can be clipped to the studs. Light switch can go anywhere you want.

If you want the IP66 rating to be maintained, then the correct glands etc. must be used. However exceptionally unlikely that IP66 is actually required.

What electrical items will actually be used in this garage?
How is power eventually going to be supplied from the house?

 

[winston1]

And you don't need a consumer unit in the garage either. The lights can be run off the ring via a switched fused connection unit.
If someone tells you you would lose lights with a trip, yes you would but you would also with a power cut, so if that is a problem fit battery backed emergency lights.

 

[Nick M]

Hi Winston,

Many thanks for your replies

Grossly oversized, 1.0mm would be the usual choice.

Lol - I have some 1.5mm cable from a previous project hence the plan - better too much than too little!

What electrical items will actually be used in this garage?

I'll be running woodworking kit, so the maximum I'd imagine at the same time is a table saw (draws 15A when it starts up according to manual) + dust extraction (heavy duty vacuum cleaner which I'd guess to be 3-5A) and perhaps something on recharging. Plus lights of course.

No, provided they are in the correct zones.

Could you explain what you mean by this please? Sorry!

How is power eventually going to be supplied from the house?

I'm envisioning an armoured cable run either along the base of a boundary wall, or dug under the back lawn, terminating at the existing consumer unit.

Whether the existing supply will cope with an extra 40A or not is another question...

 

[ban-all-sheds]

I have some questions...

One for you, which is important as it has a bearing on everything that you do is do you intend to apply for Building Regulations approval?

An initial quote was in the order of £1k which was enough to put me off doing it this year.

But your lack of knowledge will also prevent you from doing it this year, i.e. I don't think that you'll be able to learn enough in what remains of this year to become competent enough to design and install circuits, CUs, sub-mains etc.

I'd like to do things as close to regs as I can so that it doesn't all need re-doing when I have the cash to have it hooked up properly.

As soon as you apply power to it it is "hooked up", and it must be done just as properly, and just as safely, and with just as much testing and certification.

And your "extension lead" needs to be properly installed, and of the right cable type too.

The work you want to do is not a trivial job, and I can assure you that it involves knowing far more than you think it does.

Asking questions here can be a useful part of a learning process, but they are not a substitute for proper structured studying. The key term there is "learning process" - you cannot learn all the things you need to know just by asking questions here. It isn't structured enough - it won't provide you with a way to progress where each step builds on what you learned before.

You can't carry out a job of this magnitude by asking whatever random questions happen to occur to you. You've already shown that you have some large grey areas - what if you get something wrong because you have no idea your knowledge is wrong? What if you miss something because you simply have no idea it even exists, and just don't realise you don't know it?

• [wiki]Electrics%3Aindex[/wiki]
  
  
• [wiki]Electrics%3Abooks[/wiki]
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/electricity.html
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/domesticinstallations.html
  
  
• http://www.tlc-direct.co.uk/Book/1.1.htm

I suggest you get stuck into the last link right away - it won't give you design ideas, and unfortunately it doesn't refer to the current edition of the Wiring Regulations, but it's free, and will still give you a good grounding which you can augment with more up to date publications.

 

[Nick M]

Hi,

Thanks for your reply. It's perhaps not what I wanted to hear (I'd have preferred "go ahead, it's not that hard and you'll be fine") but I think it is good advice.

The last link you gave is very useful, I now know all about the zones

To answer at least one of your questions directly...

do you intend to apply for Building Regulations approval?

Yes, I want to get it done properly.

As such, I figure it's going to have to be signed off by an electrician, so I may as well talk with one sooner rather than later.
I'm meeting on Saturday with someone who's been highly recommended to talk about what is possible for me to do, and what isn't.

I think it strikes the right balance between the complexities you rightly point out, my desire to get on with this and keep costs down, and the fact that I'd really like to do this all myself!

Thanks again

Nick

 

[securespark]

40A is one heck of a supply for a garage.

I installed one in a large shed in 2005 and when I went back a couple of years later to visit, I checked with an ammeter and the max load was more like ¼ of that!

 

[ban-all-sheds]

40A is one heck of a supply for a garage.

He's going to need a 16A circuit, at least, just for his table saw.

What upstream device would you recommend to get discrimination against a 16 or 20A breaker in the garage?

 

[Risteard]

What upstream device would you recommend to get discrimination against a 16 or 20A breaker in the garage?

Not any type of BS EN 60898 circuit breaker anyway.

 

[JohnW2]

He's going to need a 16A circuit, at least, just for his table saw.

I'm not sure that a circuit necessarily has to be 'rated' for the start-up current of a power tool. I would imagine that many power tools which have a running current considerably lower than 13A, and are supplied via a 13A-fused plug, have a start-up current at least as high as 15A (which the OP has said is the start-up current of his saw table). That start-up current implies a running current well under 13A.

Kind Regards, John

 

[ban-all-sheds]

That's true.