Garage Discrimination help

[leedunning]

Hi, I'm looking for some help on wiring my garage at home.

I'm currently training to be a electrician and I'm going to wire this up.

2 x 13a sockets on a radial (2.5 t&e, 20a mcb
2 x 40-60w light plus switch (1.5 t&e, 6a mcb
Main garage fuse is 63a rcd

My main concern is where and how do I work out discrimination for the CU in the house.
It will be wired into a spare way in the house.

also can I wire this in 2.5 0r 4mm t&e protected in conduit or does it have to be swa no matter what.

I'm looking really on information on where to find this information

 

[Octopus]

Hi, I'm looking for some help on wiring my garage at home.

I'm currently training to be a electrician and I'm going to wire this up.

2 x 13a sockets on a radial (2.5 t&e, 20a mcb
2 x 40-60w light plus switch (1.5 t&e, 6a mcb
Main garage fuse is 63a rcd

My main concern is where and how do I work out discrimination for the CU in the house.
It will be wired into a spare way in the house.

also can I wire this in 2.5 0r 4mm t&e protected in conduit or does it have to be swa no matter what.

I'm looking really on information on where to find this information

Are you sure?

 

[GLENNSPARK]

Hi, I'm looking for some help on wiring my garage at home.

I'm currently training to be a electrician and I'm going to wire this up.

2 x 13a sockets on a radial (2.5 t&e, 20a mcb
2 x 40-60w light plus switch (1.5 t&e, 6a mcb
Main garage fuse is 63a rcd

My main concern is where and how do I work out discrimination for the CU in the house.
It will be wired into a spare way in the house.

also can I wire this in 2.5 0r 4mm t&e protected in conduit or does it have to be swa no matter what.

I'm looking really on information on where to find this information

Lee..

get an electrician in will you....

be on hand to help him ...and you can watch what he does...ask him a few questions (explain beforehand you are training to be an electrician)...and you may learn summat by the end of the day....

but just looking at some of the stuff you have asked/put in your OP tells me you aint competant at the mo.....

 

[Darkwood]

Just excusing you obvious blunder shown in post 2 what discrimination are we discussing here ?

Between mcb ratings or rcd's?

If the latter then you have a design issue as you shouldn't have 2 x 30mA rcd in series if you have you need to change the design.

Please clarify what means and size of overload protection you are using to protect the garage supply?

 

[leedunning]

hi maybe I wasn't that clear, the garage will be on its own CU, as wrote in the opening paragraph, on the circuits describe, which everyday of the week are fine.

The question really is the rating of the cable and the mcb in CU in the house.

 

[Octopus]

hi maybe I wasn't that clear, the garage will be on its own CU, as wrote in the opening paragraph, on the circuits describe, which everyday of the week are fine.

The question really is the rating of the cable and the mcb in CU in the house.

No you didn't - or if you think you did you need to make your posts 110% clearer.

Back to the cable, size AND type, and MCB - what do you think?

 

[Darkwood]

Domestic install rarely if ever achieve full discrimination between similar fuse styles regardless of rating

Off top of my head a 4amp mcb would give full discrimination to a 63amp but most other mcb's higher than 4 or 6 will only achieve partial discrimination so regardless of rating its down to pot luck if a fault trips the final circuit breaker or the front end device. The greater the divide between the current rating the more the odd are in your favour.... you would need to fit oversized supplies in on hrc or mccb front ends to achieve this but to do this these would need to overate the DNO fuse in most domestic cases.

 

[GLENNSPARK]

Lee..

whats the earthing arrangements ?

 

[leedunning]

Tn-c-s

 

[GLENNSPARK]

so Lee..

is there any extranious in that garage?

look...your best bet here is to use a SWA....go for a 4/6mm CSA 3 core...how long is the length of run?

go for an armoured.....come off an unprotected way top end...give it 32A...

then into the sub board utilising your 30mA 63A RCD as the incomer...with your 20A and 6A for your finals..

if theres extranious in that garage then get ready with the 10mm CSA G/Y....

 

[jackhammerJIM]

any bonding required in the garage lee ?

 

[leedunning]

Nothing required apart from CPC, No extraneous metal parts

 

[GLENNSPARK]

any bonding required in the garage lee ?

lol....

its `extended PME` time....lol...

its about time this subject came along...havn`t seen it posted for a bit...lol...

can you cant you?..lol...

- - - Updated - - -

Nothing required apart from CPC, No extraneous metal parts

well.....follow the guidance i have issued at #10...

- - - Updated - - -

without the 10mm G/Y

 

[leedunning]

length of run is 10M

 

[leedunning]

Glenspark thanks for the information, as soon as I posted this I knew I would get slated on here really, but hey my shoulders can take it, beats getting shot at every day in afghan.

 

[Octopus]

length of run is 10M

Think about length of run
Route of cable (inside house and outside)
Design load for garage now and future

then post your thoughts!

 

[Darkwood]

With all respect lee - i answered your question you initially asked it seems to have evolved that kind members have worked out the whole job for you bringing up issues you probably hadn't even thought of... i would take these kind gestures as a learning curve that you really need to back into learning your theory, we don't mind helping but we will also tell someone when they need more experience before attempting projects.

Do you not have an apprenticeship your work mates would be the best source for this info as they can usually give you practical examples on jobs you have done or are going to do. If you now understand the reasons why using theory then fine but usually been spoon fed answers doesn't learn you anything.

 

[leedunning]

very true mate, I don't want to be told the answers, rather know the theory to back it up, I'm currently at college and working full time, trying to get with a local spark to get hands on experience.

 

[GLENNSPARK]

very true mate, I don't want to be told the answers, rather know the theory to back it up, I'm currently at college and working full time, trying to get with a local spark to get hands on experience.

Lee...in this case with this garage feed you are proposing even though I and others have basically given you the info required how abouts you stand back a little....get an electrician in as i suggested at #3...you could help him....he will give you advice...and will be able to explain whilst carrying out the work...so you not only get the theory...but the visual as well....sometimes this helps when trying to understand something...being able to actally see whats going on...as well as just being told/reading about it...

and dont forget an RCD isn`t a fuse....which is what i think Mr. Murdoch was getting at...

 

[Simonslimline]

The trainee section on this forum is very handy for learning and posting questions. Lots of helpful members in there.