garage Electrics

[keith70]

i've just built a detached garage and about to install the electrics to it and could do with some advice/pointers as to whether i'm doing it right
from the main consumer unit 6mm T&E buried underground(450mm deep protected in armoured sheath) 15m long
Connected to a 100A 5 way consumer rcd unit
off this will be a
1. ring main of 3 double sockets(6mm T&E with a 16A MCB)
2. lighting circuit (1.5mmT&E with 10A MCB)
3. electric garage door (6mm T&E with 16A MCB)
4. outside socket(6mm T&E with 16A mcb) this will have a fused switch inside the garage to isolate it
5. low voltage garden lights will be added at a later date
any exposed wiring will be in plastic conduit down the walls or fixed to the joists
any advice or hints would be welcomed
i hope to get a friend of the family to check it over and pass the "p" regs although i don't want to put on him for doing the work
thank you in anticipation
Keith

 

[ibruceuk]

Hi Keith,

Have you got a job lot of 6mm T&E? You seem to want to use it everywhere!

Ok, from the CU, you should use 3 core SWA (armoured cable) for the underground run; it would be much easier than trying to run sealed conduit. Put it on a 32A MCB (there's a debate whether or not it should be on the RCD side or not.

In the garage run it into your CU with an RCD main switch.

Then run your ring (making sure it is a ring) in 2.5mm T&E on a 32A MCB then your lighting on 1.5mm T&E on a 6A MCB. Your garage door on a 16A radial in 2.5 mm T&E and finally your outdoor socket on another 16A radial via a SFCU.

what are your eartrhing arrangements? It does make a difference.

Hope this helps.

 

[Steve]

You mntion 6mm² a lot. This is not ness. for a ring main or socket radial, in fact, it only serves to complicate wiring at the terminations.

DO NOT bury T+E underground. You need SteelWireArmoured (easiest option) or T+E in earthed metal conduit (not for the faint hearted). (On re-reading, what do you mean by "protected in armoured sheath"?)

Dont forget to earth the armour in the sheath (this is its main protection) and terminate the cable properly with glands.

For 3 double sockets, a radial is all you need, wired in 2.5mm². Use a 20A MCB. Cant your garage door be on the same circuit as the sockets?

Lights: are you really going to have 10A worth of lights? how big is your garage????

You haven't mentioned what you are wiring this setup to, and whether you are exporting the earth from the house. What sort of earthing system does the house have?

And do check with the friend of the family first, he may not want to check off someone else's work, and under law he shouldnt, so worth asking first.

Many answers in for reference.

 

[Big_Spark]

i've just built a detached garage and about to install the electrics to it and could do with some advice/pointers as to whether i'm doing it right
from the main consumer unit 6mm T&E buried underground(450mm deep protected in armoured sheath) 15m long
Connected to a 100A 5 way consumer rcd unit
off this will be a

The cable should be SWA not T&E and I would suggest that from your other comments you would be advised to increase this to 10mm²

1. ring main of 3 double sockets(6mm T&E with a 16A MCB)

If it's a ring, then 2.5mm² is sufficient. Terminating 6mm² into a socket under such conditions will be very problematic. Further, this circuit would be better protected by a 32A 30mA RCBO.

2. lighting circuit (1.5mmT&E with 10A MCB)

Unless you have a LOT of inductive load on the lighting circuit, the 10A MCB is too large. It should be a 6A Type B MCB

3. electric garage door (6mm T&E with 16A MCB)

Again you are going over the top, 6mm² is too large if the supply is only required to be 16A. I would suggest that you supply this with 2.5mm² and drop the breaker size to 10A, as this will likely be all that is required for the motor.

4. outside socket(6mm T&E with 16A mcb) this will have a fused switch inside the garage to isolate it

This socket should be protected by an RCBO, or the socket should be the MK Masterseal type that incorporates a 30mA RCD for protection. Again 6mm² is too large and not required, 4mm² will be sufficient for a long run, but if less than about 10 meters I would suggest 2.5mm² and a 16A 30mA RCBO for protection.

5. low voltage garden lights will be added at a later date
any exposed wiring will be in plastic conduit down the walls or fixed to the joists

This is OK, but any cable you bury in the garden should be SWA.

Any advice or hints would be welcomed
i hope to get a friend of the family to check it over and pass the "p" regs although i don't want to put on him for doing the work
thank you in anticipation
Keith

I would suggest you get an electrician to do the work so it is done properly and safely, regardless of part P. It is obvious from your post you have very little experience in this area, and the safety implications are huge.

 

[Steve]

4. outside socket(6mm T&E with 16A mcb) this will have a fused switch inside the garage to isolate it

This socket should be protected by an RCBO, or the socket should be the MK Masterseal type that incorporates a 30mA RCD for protection. Again 6mm² is too large and not required, 4mm² will be sufficient for a long run, but if less than about 10 meters I would suggest 2.5mm² and a 16A 30mA RCBO for protection.

He's already got an RCD CU, so this shouldnt be nessecary.

 

[Big_Spark]

Crafty, the socket is the most likely one to cause a fault due to misuse or accident, it is GOOD PRACTICE to protect this socket with it's own RCBO.

The Main switch of the Consumer unit should be a 100mA 80A Type S RCD, and at the supply end inside the house the cable should be protected by a 80A 300mA Type S RCD.

 

[keith70]

thank you all for the the prompt replies
the 6mm T&E buried with armoured sheath was a long winded way of saying SWA which what i meant to say
as for using 6mm i got confused and can understand everybodys comments about it and will be using 2.5mmT&E
the lighting circuit i propose to have is to have 2 florescent lights inside
could i run 2 PIR outside lights off this circuit as well?
the outside socket is going to be close by, less than 2m so i will go by big sparks and crafty's comments
about the earthing can i run a separate earth from the main cu with the SWA cable to my cu box in the garage or do i have to do anything different
thank you all for your help and advice it is most appriceated
keith (i'm not as emptyed headed as my posts make me out)

 

[Steve]

Just use the earth in the cable. If you're exporting the house earth, make sure to earth both ends of the armour, as well as using the earth core in the cable.

What rating are the PIR lights? You may need a seperate 6A circuit for these, if they are 500w each. If they are lower than 500w, they can be put on the existing circuit IMO.

BigSpark, I was going on the impression that this install didn't have an endless budget, and assumed the OP was going to use a 30mA RCD to protect the whole lot, just at the shed.

There is no need - and i would certainly call it overkill - to have a 300mA time delay RCD at the house, as well as a 100mA time delay RCD at the shed! Just wasting money. The cable to the shed doesn't need RCD protection AFAIK.

Just stick a 30mA RCD as the incomer on the shed CU, I would call that sufficient, and certainly better protected than a lot of installs.

 

[L.Spark]

I would suggest you get an electrician to do the work so it is done properly and safely, regardless of part P. It is obvious from your post you have very little experience in this area, and the safety implications are huge.

So what was the point nitpicking and telling him what he should do if he's best advised to get an electrician..

 

[Steve]

I would suggest you get an electrician to do the work so it is done properly and safely, regardless of part P. It is obvious from your post you have very little experience in this area, and the safety implications are huge.

So what was the point nitpicking and telling him what he should do if he's best advised to get an electrician..

some of the DIYers that post on here are hell-bent on doing the work themselves, despite the best efforts of regular posters telling them to get a Pro in for their own safety. Thus it is best to advise them to get a spark, while telling them how to safely do it themselves, for their own safety, should they wish to still do it.

 

[L.Spark]

some of the DIYers that post on here are hell-bent on doing the work themselves, despite the best efforts of regular posters telling them to get a Pro in for their own safety. Thus it is best to advise them to get a spark, while telling them how to safely do it themselves, for their own safety, should they wish to still do it.

OK..Fair point

 

[Big_Spark]

I would suggest you get an electrician to do the work so it is done properly and safely, regardless of part P. It is obvious from your post you have very little experience in this area, and the safety implications are huge.

So what was the point nitpicking and telling him what he should do if he's best advised to get an electrician..

I told him were he was going wrong and then told him to get an electrician in to make sure it's done right..Matt, why do you have a problem with this..you hung over?

 

[L.Spark]

I told him were he was going wrong and then told him to get an electrician in to make sure it's done right..Matt, why do you have a problem with this..you hung over?

Not at all, some one kindly pointed it out to me, it looks like you're just being picky to me Jim, there’s being helpful and then there’s just taking the ***

 

[Big_Spark]

Well obviously I'm just an arshole then as I think it's wise to point out when someone is doing something wrong that will cost them money uneccessarilly and potentially be a hazard to themselves and others, and rather than just tell them they are wrong I think it polite to explain so that they understand..

But hey..I'm an arsehole, what do I know..

 

[L.Spark]

Well obviously I'm just an a*****e then as I think it's wise to point out when someone is doing something wrong that will cost them money uneccessarilly and potentially be a hazard to themselves and others, and rather than just tell them they are wrong I think it polite to explain so that they understand..

But hey..I'm an a******e, what do I know..

Now you're just being stupid, as for costing them money perhaps you ought to look at you're own posts, that's wasting money.