Garage Electrics

[adam1984]

Afternoon all.

Currently studying C&G 2330 L3 and nearing the end of my course. Today at work a collegue asked for some advice on running power to his garage.

Now my advice would be this (not told him yet). Could you correct me where I am going wrong?

I dont know the distance the garage is from the house but he is a local guy so I would say only 2 metres max (judging by most house's around here)

2.5 / 4mm2 SWA?

Run from dedicated MCB in CU - 32a?

Cable run outside underground to 600mm depth with warning tape.

SWA terminated in dedicated garage CU with RCD, 1 x 6a MCB for lights and 1 x 16 or 20a MCB for sockets.

How does that sound?

(Not ure who will be doing the work. He may ask me but i wont do it until i am finished at college and gained the 17th and Napit / Elecsa registration)

Adam

 

[Andy™]

2.5 on 32a is no good. which i would expect someone nearing the end of 2330 to know

apart from that, doesnt sound too bad. but when about the earth? if its TNCS, you shouldnt be exporting it

 

[a1]

[quote name='Andy

 

[Andy™]

Why not?! :run :innocent

you better hope Rodney doesnt see that!

 

[a1]

I only put in on there to set our Rodders off.

 

[adam1984]

[quote name='Andy

 

[Andy™]

Schoolboy error on the 2.5mm / 32a! Apologies.Would you mind elaborating on your earth question with a brief explanation to help me get a better understanding please?

search 'exporting tncs'. should keep you occupied for a few days

 

[Doc Hudson]

This work would also be notifiable under Part P building regulations.

Doc H.

 

[SLIPSHOD & SLAPDASH]

2M would be fine, no problems

 

[Sidewinder]

Build a wooden walkway the 2m between the house and the garage, then you are not "exporting" the TN-C-S...

 

[tonyyoung]

Hi Adam,

If i were you i would suggest some S.W.A ( Steel Wire Armored) and use the correct glanding kit. 2.5mm 3 core, 16Amp MCB but take it from the RCD side of the Fuseboard.

Think the regs state that if a socket is going to be used for external use it needs to be RCD protected. So going on that theory a garage is bound to have sockets for external use.

The SWA gives all the protection you need and by the sound of it you do not need to much so the cost would be worth it.

Hope that helps

Tony

 

[NozSpark]

Hi Adam,If i were you i would suggest some S.W.A ( Steel Wire Armored) and use the correct glanding kit. 2.5mm 3 core, 16Amp MCB but take it from the RCD side of the Fuseboard.

Think the regs state that if a socket is going to be used for external use it needs to be RCD protected. So going on that theory a garage is bound to have sockets for external use.

The SWA gives all the protection you need and by the sound of it you do not need to much so the cost would be worth it.

Hope that helps

Tony

I'm afraid I wouldn't do it like this.

Yes to SWA, but no to RCD side of board, and no to 16A MCB,,,, you don't know what the customer wants and there isn't a one fits all solution. What if they are a weekend welder or are into pottery and have a kiln? They could be like a recent client of mine who wanted a shower in the garage, that ended up with a 20m 25mm 3core submain!

I would then run the SWA into a metal clad "garage board" with RCD protection for the final circuits.

This is of course working on the premise that it's a TNS or TNC-S installation and that there are no extraneous parts in the garage; TT or extraneous parts will change everything!!!!

Also where socket outlets are installed in where they are not under supervision or for a single fixed appliance then generally they will all require RCD protection?

 

[Sidewinder]

Tony,

There are a few issues with your suggestion that good design would eliminate.

As Noz suggests we don't know what the the OP's client is looking for.

The board may not have an "RCD side".

If you do as you suggest a fault in the garage could trip out all of the circuits connected to that RCD, obviously depending upon the fault, this would be very inconvenient with the RCD in the house, and we don't know the configuration of the circuits on the house board, the supply type etc.

My preferred choice would be a separate sub main direct off the main tails and it kept completely separate to the house install.

 

[Doc Hudson]

Excluding TT installations, there is no direct requirement to RCD protect a SWA sub main, nor any surface wiring. Although there is a lot of hype about RCD nuisance tripping, it is sensible to avoid including unnecessary sharing of RCD's on an installation. This will assist discrimination and convenience issues in the event of faults.

Doc H.

 

[adam1984]

Hi All,

Many thanks for all your input.

Spoke with the Lecturer last night and we discused this.I gave my propsel and asked what he would do if it is a TNC-S install and this is what was said:

4mm SWA on a 16a MCB (Lets just say he might plug the hoover,jet wash, mower in but nothing bigger then 13a) to garage CU

Banjo and Fly lead the SWA at House CU

Garage CU to have 1 x RCD, 16 and 6a MCB

Run garage Earth on a TT

He said also to NOT banjo and fly lead the SWA at the garage - just to cut back the wire armour and tape off. - whats the reason for this?

Also I understand that this is Notifiable. As said I will not be undertaking any notifiable work in houses until I am registered. I do get asked to do things that are notifiable and turn them down or point them in direction of other electricians I know (who are registered). It is hard as extra money is nice to have but if I go down the wrong routes now then its not a good start to a career I want to do.

On a side note as well its also nice to be able to ask some questions and not be shot down with - Are you competant? Should you be doing this? what did the LABC? call in someone who knows what they are doing? etc.. that you get form other forums. I have been at college for nearly 3 years and we do learn a lot but in my opinion not enough of site situations etc. We have spent god knows how long on motors, power factors, inductance, Capacitance etc (The Science) and not enough on going through the likes of the OSG and real site examples of installations.

Once again thank you for the responses.

Adam

 

[Andy™]

He said also to NOT banjo and fly lead the SWA at the garage - just to cut back the wire armour and tape off. - whats the reason for this?

do NOT do this. i think you need a new lecturer...

yes to the no banjo / flylead, but do not just cut back the armour. for a start, any movement and the armour will start to damage the insulation

 

[steptoe]

to a point Andy. but at least he told him to isolate the earth and TT it, unlike a lot of lecturers,

adam, there are a few tutorials on how best to terminate the SWA at the garage end on here somewhere, but be fricked if I know where to find them.

on the whole your lecturer is correct though in telling you do NOT connect, or have accessible, the armour at the garage end .

 

[adam1984]

Sorry I made it sound cruder than he meant it.

He did say to make sure that the wire armour didnt come into contact with any conductive parts and that the wire armour was cut back and taped tightly.