Is RCD needed at both ends of armour feed to outbuilding

[chrisbwx]

Hi - first post.

I am going to carry out a sub main installation from a main CU in the house, to a garage, (15m from main CU to garage sub board).

The CU in the house has no RCD protection.
The garage will have a local TT, and the sub board will have 30mA RCD as main switch.
The SWA cable 10mm2 will come off a 45A type B breaker. The steel wire sheath will be earthed via gland/banjo at main CU earth.

My question is: given that all sockets/light ccts in the garage will have local RCD protection - do I need to upgrade the main CU to include RCD or RCBO on the SWA feed to the garage? My thinking is that if someone stabs through the armour there is no RCD protection for the inner conductors.....

No doubt this question has been asked before and apologies if this is old, old ground but is the first time I have installed this arrangement on an old board with no existing RCD.

I am domestic installer 2 years in.

 

[not clever]

A DI 2 years in..............you need to go back to college

 

[telectrix]

all i'll say is that SWA does not itself require RCD protection, and as above, you should know this if you are carrying out paid work. FFS.

 

[HandySparks]

What's the earthing arrangement of the main supply?

 

[telectrix]

yep. why TT if you have a perfectly good TN system existing? i can see this thread turning sour.

 

[not clever]

Hi - first post.

I am going to carry out a sub main installation from a main CU in the house, to a garage, (15m from main CU to garage sub board).

The CU in the house has no RCD protection.
Not an issue, but what is the earthing system at the house?
The garage will have a local TT, and the sub board will have 30mA RCD as main switch.
Will this comply with the regulations & is it an insulated or metal clad board?
The SWA cable 10mm2 will come off a 45A type B breaker.
Not a problem.
The steel wire sheath will be earthed via gland/banjo at main CU earth.
As it should be, what is the house cu (make & construction), Piranha™ Earth Nut & bin the banjo.

My question is: given that all sockets/light ccts in the garage will have local RCD protection
Will this comply with the regulations?
- do I need to upgrade the main CU to include RCD or RCBO on the SWA feed to the garage? My thinking is that if someone stabs through the armour there is no RCD protection for the inner conductors.....
And this is why the thread should be in the DIY section & you my Electrical Trainee need a college course or somebody to hold your hand.

No doubt this question has been asked before and apologies if this is old, old ground but is the first time I have installed this arrangement on an old board with no existing RCD.
If you have "installed this arrangement" on cu's with an RCD then I point you to the above comment.

I am domestic installer 2 years in.
Fair play to you. maybe this whole thread should be given to the DCLG next time they speak to the scheme operators, wonder what Ms Clancey would make of it?

See my red, sorry but you sound out of your depth.

 

[chrisbwx]

main supply earth is TNS, attached to a ropey old bit of builders band.

Ze to the sheath is 0.25.

Was advised by NICEIC engineer that TT is the preferred way to earth any outbuilding supplies. And understanding from regs that if you have potential extraneous conductive parts coming in - in this case they have cold water supply in garage then TT is a must.

 

[Badged01]

all i'll say is that SWA does not itself require RCD protection ....

Provided it meets the disconnection times ....

 

[Darkwood]

Like others have asked what is the supply characteristics to the house?
If tncs - the what is the construct of the garage?
Does the garage have any metal services coming into it?

Also like others there are several areas to look at regarding this kind of install and you haven't provided the necessary info and can only assume you are not aware it is needed thus would conclude you get back into your college books and swat up.... i could understand 1 question about the set-up as we all need a little nudging at times but not the several questions you asked as this shows lack of competence.

 

[amlu]

stick it on a separate feed from main consumer unit using RCBO....

 

[spark 68]

stick it on a separate feed from main consumer unit using RCBO....

Why RCBO ?

 

[Badged01]

Why RCBO ?

Coz they are the 'in' thing at the moment .......

 

[spark 68]

What I meant was the supply is TN-S and using armoured cable for the sub-main.

I wouldn't bother TTing it at the outbuilding end as the Bonding arragement is not as onerous for TN-S as it is for PME/TNC-S, plus I am not a fan of remote RCDs.

 

[Farmelectrics]

The in thing I guess your joking. They provide additional protection and reduce the risk of electrical shock

 

[SPARTYKUS]

Fee fy foe fum, I smell the blood of a troll

or someone that knows exactly what they are talking about!

if not, I return my tankard to the bar. Emptied.