Yep, its another shed question , but with pretty pictures.

[kwikfix328]

Can one of the resident experts take a quick gander at these couple of pictures for a proposed shed install (in Scotland).

All pretty straight forward but not sure of the easiest way of doing the lighting arrangements.

Lighting:
I already have the 60" Flo tube installed ( currently powered when required by an extension reel - not ideal ) , This needs to be controlled by a single switch by the door.

I also want a 100 or 150 watt PIR controlled security/area flood which will be switched on all the time and just be controlled by the units own PIR/ movement detector.

I may also add an external switched dome light with lo energy bulb for when I sawing bits of wood outside at 11 pm in the summer as we do...

Supply to shed:

I've rummaged in my box of bits and pieces and found a couple of 63A 30ma 'Shower' RCD's . I could incorporate one in the circuit if required ( maybe to protect the buried cable ??)

I already have some 4mm 2 core SWA cable that i could use ,or would buying some 3 core for this be better, it is only about £20 for the amount i need so safety is my main concern here

Shed Consumer:
I've already got a 2 way MEM 2000 Garage CU with 6A & 16 A mcb's with 63A 30ma combined main isolator switch/RCD.

http://photos.imageevent.com/sidandcoke/generaldumpinggroundforgashpiccys/shed option 1.JPG

http://photos.imageevent.com/sidandcoke/generaldumpinggroundforgashpiccys/shed option 2.JPG

 

[Lectrician]

You show 2.5mm cable for the lighting circuit. 1mm or 1.5mm is fine.

You show a joint box to join the two 1mm cables. I would take both 1mm's back to the CU and put them in the same MCB, or loop from one switch to the other. No need for a joint box at all.

You show a Fused Connection Unit for the flood. No need.

You show a ring final circuit on the 16amp breaker. A 20amp radial circuit would be fine in 2.5mm (you could use 16amp if you wish with the 2.5mm).

What is your installation method? Conduit?

 

[Lectrician]

Did not see your second pic, but my comments still pretty much remain the same

 

[kwikfix328]

Thanks for your comments, much appreciated

You show 2.5mm cable for the lighting circuit. 1mm or 1.5mm is fine.

I already have enough spare 2.5mm²,( and 4mm² ) from other jobs, I'd have to buy in smaller cable so will use what I've got.

You show a joint box to join the two 1mm cables. I would take both 1mm's back to the CU and put them in the same MCB, or loop from one switch to the other. No need for a joint box at all.

Noted, cheers I didn't think of that , I'll see what looks easiest to do. I have already got a spare cable joint box in my gash box so I won't be buying one especially for this.

You show a Fused Connection Unit for the flood. No need.

I've already got one going spare, so seemed like an easy way of isolating the Flood and making transition from fixed to flexi cable.

You show a ring final circuit on the 16amp breaker. A 20amp radial circuit would be fine in 2.5mm (you could use 16amp if you wish with the 2.5mm).

Noted, I'll see what is easiest to install. Nice to know i have some choice here. So basically i can omit the final run of cable from the external socket back to the CU if i wish ? ( I'll prob stick to a ring though).
There will be a 3000w tumble drier on this circuit, ( in constant bloody use ) plus , say my most powerful power tool ( my 2000W Table saw ) so upto 5000w in normal ( but infrequent) use . I'll probably use 4mm to over spec the circuit then i can upgrade the supplied 16A breaker if it regularly trips.

What is your installation method? Conduit?

I haven't decided yet. I will be using 2.5mm or 4mm T&E for all internal wiring as I've already got it. I was going to just clip it to the internal structure of the Shed using standard cable clips.

A few bits of plastic conduit and end fittings won't cost much though for these small circuit lengths . I have both white plastic surface mount sockets and metalclad units , in my gash box so can use either, I was planning to use the metalcald fittings.

Do I have to use conduit for this, I don't mind if i have to. But will have to go and buy it in. It is pretty much the only thing i don't already have as i've never needed it before.

Thanks again.

 

[Lectrician]

Noted, I'll see what is easiest to install. Nice to know i have some choice here. So basically i can omit the final run of cable from the external socket back to the CU if i wish ? ( I'll prob stick to a ring though).
There will be a 3000w tumble drier on this circuit, ( in constant b****y use ) plus , say my most powerful power tool ( my 2000W Table saw ) so upto 5000w in normal ( but infrequent) use . I'll probably use 4mm to over spec the circuit then i can upgrade the supplied 16A breaker if it regularly trips.

16 or even 20amp is not going to give you 5kw.

No point making it a ring at all if using a 16amp or 20amp breaker. It just does not make sence to.

If using 4mm, certainly no need for a ring - 4mm can be used as a radial on a 32amp breaker. (or smaller).

 

[kwikfix328]

Cheers for that, a radial circuits it is then.

In fact the Tumble drier is going to be sited on one side of the CU and my other sockets will be on the other side so I will probably just have two seperate radials coming out of the CU, one for the tumble drier , the other for the general use socket outlets.

I will also configure the lights as two seperate Radials.

Final Qustion about the Conduit, do I need it or not ?
Looking at what i have already it is the only thing i would need to buy in if required.

One thing i did forget to ask was about getting the cable from the Main CU to the Shed. I have heard about folk using an external Junction box and using SWA out side and T&E inside, this seems a bit complicated to me. I was just going to drill a hole through the house wall and go with one unbroken straight run of SWA from House CU to Shed CU, (less connections to possibly corrode and go wrong).

Any views about protecting the SWA From the House . I have found not one but two 63A 'Shower' RCD's with enclosures in my Gash box, Can't even remember buying them . I'd prefer not to use them just to cut the amount of work and number of connections down, but they are there if needed.

Final Picture of my proposed circuit:
http://photos.imageevent.com/sidandcoke/generaldumpinggroundforgashpiccys/shed option 3.JPG

 

[ban-all-sheds]

One thing i did forget to ask was about getting the cable from the Main CU to the Shed. I have heard about folk using an external Junction box and using SWA out side and T&E inside, this seems a bit complicated to me. I was just going to drill a hole through the house wall and go with one unbroken straight run of SWA from House CU to Shed CU, (less connections to possibly corrode and go wrong).

Do the CU's have enough space for you to terminate SWA into them, and are they strong enough?
An alternative, if you don't want to join cables, but can't gland directly into the CU is to put a small metal adaptable box next to the CU, touching it, terminate the SWA in that but leave the central core long and take that though a grommeted hole into the CU, along with a flylead for the banjo or Piranha. I know this will mean you buying something, but you'll get over it...

Any views about protecting the SWA From the House .

I don't think it's necessary, but some people do - your call, but..

I have found not one but two 63A 'Shower' RCD's with enclosures in my Gash box, Can't even remember buying them . I'd prefer not to use them just to cut the amount of work and number of connections down, but they are there if needed.

You'd then have 2 30mA RCDs in series - not a good idea. If you really want to protect the cable as well, use a 100mA or 300mA time-delayed RCD at the house end.

The other thing that concerns me is the combination of rotating machinery and fluorescent lights - not always the safest. Have you thought of any other sort of lighting, or about getting a HF light?

 

[kwikfix328]

duplicate post of one below.

 

[kwikfix328]

Do the CU's have enough space for you to terminate SWA into them, and are they strong enough?
An alternative, if you don't want to join cables, but can't gland directly into the CU is to put a small metal adaptable box next to the CU, touching it, terminate the SWA in that but leave the central core long and take that though a grommeted hole into the CU, along with a flylead for the banjo or Piranha. I know this will mean you buying something, but you'll get over it...

I've got two seperate , but related projects on the go at the moment. Getting power to the shed and replacing my house consumer units.

The new split load house CU is going to be a metalcald unit. So will be able to take the SWA gland directly. It is hidden in a cupboard out of view so looks are unimportant to me, function and safety are my only concerns.
I have had a very reasonable quote from a local qualified Spark and so have decided to let him do this work, as long as i like/trust him when he pops around for a site survey next week.

He said he would happily take a look at my shed circuits and test them for me at the same time.

He also said he i can either get the hardware myself and he would fit it, or he would supply and fit. He also said that if i wanted to buy some s/h gear to fit then this would be fine also, just as long as it was in good , safe working condition and fit for purpose.
Lets face it a CU is only a box filled with user replaceable parts.

The other thing that concerns me is the combination of rotating machinery and fluorescent lights - not always the safest. Have you thought of any other sort of lighting, or about getting a HF light?

Hmmm... no. I'll just have to be careful. If i do have to do any sawing etc I tend to do it outside anyway. I am a fair weather DIY'er . Saw dust gets everywhere inside anyway.