Workshop electrics. What do I need?

[garywayne]

Hi folks, I hope you all had a good christmass and new year.

I am in the prosess of draught proofing under my stairs, but before I can finnish off I need to run cable from my consumer unit and under the floor.

When it comes to electrics I believe that I am capable to do the job. What I don't know is, what is needed, or what ratings.

In the shed I will have:-
1 x Lighting circuit. ( 6 double florescent lights).
1 or 2 x ring mains. ( With lots of sockets).
1 x Table saw, (I believe running from a 16A MCB).
1 x Bandsaw, ( depending on which one, pos running from a 16A MCB).
1 x Planner\Thicknesser.
1 x Extractor. Don't know what one.
Power tools running from ring main.

Sorry if I am dragging on a bit.
What I need to know is what size MCB will I need in the consumer unit, house side, and should it be RCD protected? What size T&E cable will I need to go from the consumer unit to the Armour cable, (What size Armour cable)? I take it I will need the same T&E from the Amour cable to the shed CU?

I think the rest is pretty straight forward.
I will be getting a part P electrician to test and I hope pass all of the electrics once I have finished.

 

[Dibs-h]

I was under the impression that the armoured cable terminates directly in the CU - but that could be a combination of intellectual intermissions and\or not paying attention.

I'm sure some knowledgeable person will be along shortly.

 

[OLD]

In the shed I will have:-
1 x Lighting circuit. ( 6 double florescent lights).
1 or 2 x ring mains. ( With lots of sockets).
1 x Table saw, (I believe running from a 16A MCB).
1 x Bandsaw, ( depending on which one, pos running from a 16A MCB).
1 x Planner\Thicknesser.
1 x Extractor. Don't know what one.



Consumer unit mcb's:- 6a lights. 1xring 32a. 2x16a dedicated
p/t, extractor unless very powerful and all other power tools use ring main,rcd main switch required.

 

[garywayne]

Thanks for replies.

Old.
Thanks for your listing. Do you know what size MCB I need in the house consumer unit that supplies the shed power, and should it be RCD protected

Dibs-h.
If I am unable to get a bit of armour cable short enough, perhaps it will be easyer to go armour all the way.

 

[Dibs-h]

Thanks for replies.
If I am unable to get a bit of armour cable short enough, perhaps it will be easyer to go armour all the way.

For some reason, I'm under the impression it would need to be armoured cable all the way, i.e. House CU to Outbuilding CU.

 

[garywayne]

I am going by what I have read.

"Armoured cable is expensive and has to be terminated at a special junction box at each end of its run, where it can be joined to ordinary PVC-insulated cable".

 

[Dibs-h]

I am going by what I have read.

"Armoured cable is expensive and has to be terminated at a special junction box at each end of its run, where it can be joined to ordinary PVC-insulated cable".

Cool - put it down to intellectual intermission\not paying attention. Good to know. Thanks.

 

[garywayne]

Your welcome Dibs.
It's nice for me to be able to help someone for a change. :wink:

 

[jlawrence]

SWA can be terminated directly in the CU - that's what the sparky did in my old house.
I'll be renewing the powerfeed to my workshop when the weather warms up. I'll be taking T&E to a junction box then SWA from the junction box, around the garden, and finally to the CU in the workshop.

 

[liam8223]

You must use armour cable if you are putting underground.
Twin and earth is not suitabe for just burying, and for the difference in cost to the difference in safety, armour cable should be used in all circumstances even if you are laying trunking in which to house the cables.

Metal consumer units ('distribution boards' when metal) can accept armour cable, with a suitable armour gland and earth banjo.

Plastic boxes however require a cheap and simple metal adaptable box in which to terminate the armour, then use meter tails or similar into the rcd.

In all of my buildings we use a 63A RCD main switch (3 phase).

The armour cable is not that expensive although if you have only ever bought T+E, maybe it will seem a little pricey.

HTH

Liam.

 

[flying haggis]

I am going by what I have read.

"Armoured cable is expensive and has to be terminated at a special junction box at each end of its run, where it can be joined to ordinary PVC-insulated cable".

not true and I hope you realise that all of this is notifiable under part P regs


another way of supplying the shed is to split the meter tails with a henley block then via a 100A switch to a CU in the shed but the sparky you employ (so you get the certificates or you need to get the building control officer at the council to sign it off)) will tell you all the options

 

[Jake]

I am going by what I have read.

"Armoured cable is expensive and has to be terminated at a special junction box at each end of its run, where it can be joined to ordinary PVC-insulated cable".

not true

What are you saying is not true?

 

[SemiSkilled]

why don't you get some advice from the spark who will test the job?

As its to an out building the first thing to look at is the earthing arrangement some elec suplliers don't let you "export the earth"

the cable required depends on

Maximum demand

The length of the run out to the shed

The method of installation O/H , U/G or in conduit ( there are
more!)

Try this link, get a coffee / tea .

http://wiki.diyfaq.org.uk/index.php?tit ... ty_outside

Lee

 

[garywayne]

Since my motorcycle accident 8 1/2 years ago, I seem to have quite a lot of spare time on my hands, (as no one seems to want to employ me), if the wife leaves me alone, (love her lots).
So I like doing things myself, you know, for something to do. I have been doing my own electrics for some years. Not by guessing, but by finding out how it's done. I did forget to mention that the armour cable will be at least 500mm (18in) under ground between the house and the shed. The junction boxes at either end will be internal and above the DPC. My house earth is the most common, TN-S. The cable distance is:
T&E 14M; SWA 8.5M; TOT = 23M max. My cabling is single phase.
As mentioned before, once I have completed the supply to the shed, and the wiring within the shed, I will then attempt to find the appropriate relyable sparks to test and hopefully pass the completed work.
All I need to know is:
1. Should the MCB for the shed supply be on the RCD side of the house CU or not? (My house CU is split).
2. What size MCB should supply the shed? Is 32Amp appropriate?
3. What gauge T&E should I use? Is 4mm sq heavy enough?
4. What gauge SWA?

In the shed I will have:-
1 x Lighting circuit. ( 6 double florescent lights).
1 x ring mains. ( With lots of sockets).
1 x Table saw, (I believe running from a 16A MCB).
1 x Bandsaw, ( depending on which one, pos running from a 16A MCB).
1 x Planner\Thicknesser.
1 x Extractor. Don't know what one.
Power tools running from ring main.

Old has given me the MCB sizes for the shed CU. So, I think that is all I need to know. For now anyway.

Um, just read through. If I sound a bit abrupt, I appologise. Not intended.

 

[OLD]

1. Should the MCB for the shed supply be on the RCD side of the house CU or not? (My house CU is split).
2. What size MCB should supply the shed? Is 32Amp appropriate?
3. What gauge T&E should I use? Is 4mm sq heavy enough?
4. What gauge SWA?


1. RCD side
2. 50a
3. 6sq mm
4. what comes with the 2 core cable.

The shed CU can be capable of taking the swa gland which saves a job.
Talk to the sparks about the design and termination arrange to run all wires and fix components then get him to terminate what you have agreed and sign off.

 

[garywayne]

Thanks Old.
You have been most helpfull. Just one thing though. I am in the process of reading the link Lee suggested and it states, If I have read it correctly, that the submain should be on the RCD unprotected side of the house CU.

 

[matt]

OK, here's my setup that's been tested by my sparky mate:

Garage approx 10m run of 6mm SWA.
Terminates in adaptable metal box at the house side cos the CU's is plastic and the SWA can stress the plastic if connected directly. 6mm T&E from the adaptable box to the CU.
CU at the garage end is metal so SWA connected directly.
The CB at the house end is: 40amp and on the RCD side.
Garage circuits are 6amp and 32 amp. I also have a 16amp in there for dedicated supply for the table saw if I ever decide to connect it up. This is a bit naughty because the total exceed the CB in the house...

Think that's it...

 

[garywayne]

Thanks Matt.

I think the reason for having the shed supply on the RCD unprotected side is so that if the house RCD trips while you are oporating you saw or what ever you still have power and lighting. If you have the shed supply on the RCD side and it trips you are in the dark and posibly in your saw.

 

[matt]

Mine is on the RCD side because it protects will cut power to the SWA in the event of an accident. If my lights go off then everything will go off too. I stick with RCD protected from the house consumer unit and install some emergency lighting if necessary. One thing NOT to do is use RCD at both ends - one can interfere with the other.

 

[garywayne]

If your power to the shed goes, ie. At night, lights go out while you are opperating machinery it is possible to slip into said machinery if the house RCD is tripped. But if the shed supply is on the RCD unprotected side and the house RCD trips you will not be effected.

I haven't finnished reading the link yet, but I am under the impresion that the supply comes off a MCB which will protect the shed supply
:? I think, then you have a RCD in the shed CU.