Garage Supply Help!!!

[Rufat]

Hi everyone.
I am new to this forum. I've just completed my C&G level 2 qualification and started on level 3.
Next week i plan to install a garage supply from the CU in the house to the two way CU in the garage.
I planned everything all wiring diagrams, layout and about to do a product list. The job will be tested by a competent person as soon as i finish it.
But before i start the job i wanted to make sure that everything is correct and need an advice on RCDs in this installation.

It's a TN-S system.
There is an old type metal consumer unit as you can see on the pic.

The supply to the garage CU is by 4mm SWA burried underground and properly terminated at both ends. The earthing will be extended to the garage from the house.

PVC 2 way CU in the garage supplying:
1) Lighting circuit 4x100w bulbs protected by 6A MCB
2)Radial socket circuit supplying 2x double sockets and a fused switch for a 200W pond pump protected by 20A (sockets will be used occasionaly for Power Tools such as hammer drill and circular saw

Cables:
1)1.5mm flat T&E clipped direct for lighting
2)2.5 mm flat T&E clipped direct for Radial

The questions is:
1) Should i add 20 MCB on non RCD side in the main CU and have a 30mA RCD in the garage connected to it?
or
2) supply the garage from existing 60A RCD and have a main switch with 6,20A MCBs in the garage (which will be easier and cost effective)

The outbuilding is only 5m away from the house.

Any advice and information much appreciated.
Regards,
Rufat

 

[guest119]

You say the job will be tested by a competent person, does that mean you dont consider yourself to be so?
How do you plan to gland an armour into a plastic consumer unit?
The existing 60a rcd is just that, an rcd and the 60a is handling current not tripping current.
Therefor if you come straight off this you will only have the main cutout (100a ?) as overcurrent protection.
2 way CU leaves no spare ways.

Boydy

 

[GLENNSPARK]

You say the job will be tested by a competent person, does that mean you dont consider yourself to be so?
How do you plan to gland an armour into a plastic consumer unit?
The existing 60a rcd is just that, an rcd and the 60a is handling current not tripping current.
Therefor if you come straight off this you will only have the main cutout (100a ?) as overcurrent protection.
2 way CU leaves no spare ways.

Boydy

with a gland, banjo n flylead....
why, how do you do it?...with a stuffing gland?...lol..

 

[Octopus]

"Will be tested by a competent person" - oh dear, here we go again. Pop corn anyone?

 

[Rufat]

Hi Boydy,
thanks for reply.
Actually you are right i'm better off with a metal clad CU in the garage (but i think i could run and gland swa to metal adaptable box (close to garage CU) from which i could run the live and eutral (insides of SWA) to the garage CU.
Overcurret protection will be pprovided by MCBs (6A and 20A) in the garage CU. and residual current protection/earth fault by RCD in the main CU that is what i was thinking.
I can do and know how to do insulation resistance and continiuty tests, but as it will be my first installation i just want to make sure there are no mistakes made.

So what would you advise on how protect my installation?

 

[Rufat]

))right as i understand you ve gone through this toppic several times and as i am new to this forum and havent got experience as an electritian i appologise for bringin this matter up.

 

[Rufat]

1) Should i add 20 MCB on non RCD side in the main CU and have a 30mA RCD in the garage connected to it?
or
2) supply the garage from existing 60A RCD and have a main switch with 6,20A MCBs in the garage (which will be easier and cost effective)

if none of above options is OK can you advise me please how to solve this situation.
Thanks

 

[Octopus]

1) Should i add 20 MCB on non RCD side in the main CU and have a 30mA RCD in the garage connected to it?
or
2) supply the garage from existing 60A RCD and have a main switch with 6,20A MCBs in the garage (which will be easier and cost effective)

if none of above options is OK can you advise me please how to solve this situation.
Thanks

Employ a competent electrician?

 

[Thefailsafe2012]

Do you want to be legging it down the garden from your shed to the house to reset the RCD everytime it trips? :angel_smile:

 

[Richard Burns]

1) Should i add 20 MCB on non RCD side in the main CU and have a 30mA RCD in the garage connected to it?
or
2) supply the garage from existing 60A RCD and have a main switch with 6,20A MCBs in the garage (which will be easier and cost effective)

if none of above options is OK can you advise me please how to solve this situation.
Thanks

At least 32A MCB from non RCD side, SWA to 30mA RCD protected CU with appropriate MCBs in garage.
You may find the circular saw inrush current trips a 20A MCB.

 

[Rufat]

Employ a competent electrician?

Ok. How a competent electritian would do it?

 

[Rufat]

At least 32A MCB from non RCD side, SWA to 30mA RCD protected CU with appropriate MCBs in garage.
You may find the circular saw inrush current trips a 20A MCB.

Great. Thats is what i needed. Thank you

 

[Deleted member 72666]

Do you want to be legging it down the garden from your shed to the house to reset the RCD everytime it trips? :angel_smile:

That is a valid argument but how often under normal use is it likely to trip? I've a similar setup and not once has it tripped in 26 years of use! (And yes it has been tested to be okay!)

 

[Rufat]

Do you want to be legging it down the garden from your shed to the house to reset the RCD everytime it trips? :angel_smile:

No of course i dont. Therefore i will follow Richard Burns advise

 

[Thefailsafe2012]

Well just thought it might be a pointer to bear in mind, only based off the fact that a shed is a shed, its outdoors, can be damp, can be home to critters, and probably more likely to trip then a nice warm dry house. That said.....

That is a valid argument but how often under normal use is it likely to trip? I've a similar setup and not once has it tripped in 26 years of use! (And yes it has been tested to be okay!)

You sir must have installed it properly the first time :ihih:

And my brown nosing is done!

Yep I would say Burnsys advise would be the one to take on board mate!