Is RCD needed at both ends of armour feed to outbuilding

[spark 68]

Why TT it though ?

With TNC-S/PME this may make financial sense in some circumstances, but with TN-S you could just use 3-core Armoured, use the armour as the CPC the core as the bond (or Vice versa), and keep the RCD local to the outbuilding which is more convenient.

The armoured cable will not need RCD protection, this is what I asked further back " why an RCBO ?"

Edit: the OP is already planning on using 10mm Armoured cable.

 

[D Skelton]

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.

main supply earth is TNS

The garage will have a local TT

they have cold water supply in garage then TT is a must

These are questions I'd expect my first year apprentice to know the answer to!

Some unsuspecting person (I'm assuming you are being paid for this work) has selected you to carry out this work for them, work that could have gone to a fully qualified spark who knows what he is doing! I'm guessing the customer has been mislead to believe that you are qualified. This makes me angry.

Back to the drawing board for you kiddo! I suggest college, 3 years minimum if you want to continue playing around with things that you currently have no knowledge of.

 

[spark 68]

The NICs advice is not much better, FFS

 

[wersolaruk]

I think u are not allowed to take a earth outside of the installation were extraneous conductive parts are bounded creating a parallel path, I am unsure on the specific but I can find this out on Monday give my guy at napit a call. I am pretty much into the solar so I have had to do domestic installation design for a while, I will post my findings on Monday or I am sure one the lads on here may clear it up. I know what you are saying as I would of done that before the napit guy specified a tt

 

[spark 68]

I think u are not allowed to take a earth outside of the installation were extraneous conductive parts are bounded creating a parallel path, I am unsure on the specific but I can find this out on Monday give my guy at napit a call. I am pretty much into the solar so I have had to do domestic installation design for a while, I will post my findings on Monday or I am sure one the lads on here may clear it up. I know what you are saying as I would of done that before the napit guy specified a tt

Ballocks, show me a reg that says this,
there is a bit of confusion surrounding TNC-S/PME, some say it is a DNO rule, but it is permissible by BS7671.

 

[wersolaruk]

Ok I will do as it states in my post I will clarify this on Monday I maybe wrong but if my governing body implies this I should at least listen, as I am not apart of the ' I know best ' department as some people will always argue the ----

 

[D Skelton]

I think u are not allowed to take a earth outside of the installation were extraneous conductive parts are bounded creating a parallel path, I am unsure on the specific but I can find this out on Monday give my guy at napit a call. I am pretty much into the solar so I have had to do domestic installation design for a while, I will post my findings on Monday or I am sure one the lads on here may clear it up. I know what you are saying as I would of done that before the napit guy specified a tt

Extend the equipotential zone then?! Just goes to show how useless these scam assessors are! Mind, aren't Napit assessors the ones that insist on flying earth leads in sockets? What a bunch of morons!

They are not applying BS7671 to their assessments, they are applying 'club rules'. Your responsibility is to ensure that the installation complies with the former set of rules, that is all! If it complies with the former but doesn't comply with the latter then that is an issue between you and them only, your installation still complies with the regs.

 

[spark 68]

They are not your "governing body" for a start, and they don't write the regs, you pay them a large amount of money so you can self certify, that is all.

 

[wersolaruk]

Large amount of money? What 400 quid? Seems reasonable to me

 

[D Skelton]

Large amount of money? What 400 quid? Seems reasonable to me

+VAT at least!

Tell me, what exactly do you get for your money other than a shiny sticker to put on your van? And don't tell me the ability to self certify, you pay extra for that privalige!

 

[shanky887614]

Extend the equipotential zone then?! Just goes to show how useless these scam assessors are! Mind, aren't Napit assessors the ones that insist on flying earth leads in sockets? What a bunch of morons!

They are not applying BS7671 to their assessments, they are applying 'club rules'. Your responsibility is to ensure that the installation complies with the former set of rules, that is all! If it complies with the former but doesn't comply with the latter then that is an issue between you and them only, your installation still complies with the regs.

What good is a flying lead?

It is earthed by the pins?

You should never need to remove the faceplate with power on anyway (test from the front etc)

 

[spark 68]

I pay similar, but why should I have to pay these parasites just to work ?
I work to BS7671, and where applicable the various building regs, of which part P is one.

 

[D Skelton]

What good is a flying lead?

It is earthed by the pins?

You should never need to remove the faceplate with power on anyway (test from the front etc)

Exactly my point when I called the Napit assessors a bunch of morons! lol

 

[wersolaruk]

It's life unfortunately nothing u can do but I make money they make money. Ur not going to work for nothing so why should they. But back to original point if another spark or assessor raises a point to me I will always listen and i wont then jump down there throat asking for reg numbers. If I am honest I don't know if it is a reg but it's something which I have been in discussion with napit hence my comment in breath was I stating I was right. Anyhow am off for a beverage

 

[wersolaruk]

Sorry I meant to say I wasn't stating I was right, this bloody iPhone keeps changing my words on predictive text, the little bugger.

 

[spark 68]

I will give you some advice wersolaruk, buy GN8 and all will be revealed, the other GNs such as 1 and 7 are very useful too, you should already have GN3

 

[D Skelton]

It's life unfortunately nothing u can do

And it's exactly that kind of attitude that allows organisations such as Napit to bend you over and sharply shaft you up the backside whenever they deem necessary in the first place! You take lethargy to a whole new level my friend!

if another spark or assessor raises a point to me I will always listen and i wont then jump down there throat asking for reg numbers.

Why the hell not? You pay them for a service (supposedly), if you want to ask questions it is their duty to answer them!

 

[wersolaruk]

Thanks for the advice I take this on board

 

[wersolaruk]

They really don't bend me over mr Skelton I can assure u that. Any how av had enough of this small talk. Bye bye

 

[Engineer54]

Ok I will do as it states in my post I will clarify this on Monday I maybe wrong but if my governing body implies this I should at least listen, as I am not apart of the ' I know best ' department as some people will always argue the ----

Before we go any further, none of the Scams are ''Governing Bodies'' even if one or two of them like to ''Think'' that they are. They are Part Pee providers, ''Nothing more''!!

As for even thinking about leaving a far superior earthing system behind in favour of a TT system, leaves a lot to be desired as far as you're technical ability goes. No concept of RCD discrimination either by the sound of it!!