Armoured cable from CU to 13amp socket in garden

I have installed an armoured cable in a parking area to power a 13amp socket with a protected 3amp spur off a radial circuit to power a bulkhead security light with PIR.

The 13amp accessory socket is rated IP56 and protected by an inbuilt 30mA RCD. The armoured cable from the house is protected by a 16amp MCB enclosed within the CU inside the property, in the RCD protected side of this dual fed CU. This PVC SWA cable connects inside the property via The armoured cable to the consumer unit through the wall via an IP65-20amp junction box.

This is where I get a little stuck.

I have procrastinated over the protection of the armoured cable itself as to wether it should be fed through the -

1./ RCD on the CU and also the RCD at the socket end.

2./ Or simply protected with the 16amp MCB with only the socket end protected by it's inbuilt RCD at the far outside end.

The question arises as every time I test the socket RCD with my meter it blows the RCD on the CU inside the house at the same time. I therefore cannot get an accurate Millisecond break reading for my electrical testing certificate.

The cable is 20m - 2.5mm 3core, buried below 500mm in a non-bedding location. The outside junction box on the wall of the property is rated at IP65 & I believe at least 20amp (Though maybe more - lost the paperwork on it.)

My question is - It is currently installed as option 1 - Is that satisfactory ?

I am using this as one of my qualifying installations for the NIC/EIC domestic installers scheme.

I take it you know all about the part pee thing. Your armour is earthed at the supply end?
In a TN system, the socket outlet in your explination is the only part required to be on RCD protection as I can be reasonably expected to supply equipment outdoors. You only need it on one 30mA RCD. For inconvenience purposes, I would be tempted to install the circuit on the non-rcd side of the CU and use the incorporated RCD.

Yes the system is TN-C-S and it is earthed from the supply end.

Ok.

I will move it to the non-rcd protected side & re-test at 1/2, 1 & 5 .


Thanks

Do you really think you're ready for NICEIC registration if you don't know the answers to these basic questions, nor what the wiring regulations say about discrimination?

Maybe read my post again & think about it.

The cable is protected to a degree. But were is the line drawn ultimately if it suffers a break, short etc including the external junction box. For instance if this box recieves a blow & the inner wires are exposed. If these were not protected, for instance on an RCD (30mA) and a direct contact occured, it would become a severe hazard especially in wet weather.

I have looked closely at all the IEE & NICEIC literature and none discusses this topic. Such outdoor electrics & with this design are widespread.

I am seeking an answer from the point of view of safety for the entire design solution.

The solution posted in response was much appreciated and I agree with it upto a point. But I was merely seeking a solution, that I have pointed out protects an individual from the entire "end to end" design should any fault alongs it's length occur. Not just at the 13amp socket end.

This a point bluerembrandt16.

In the "WHICH BOOK OF WIRING AND LIGHTING", Mike Laurence advises "not" to connect the incoming earth from the three core SWA at the outbuilding side, he does not mention anything about whether the SWA earth core should be connected at the house consumer unit side either. He proposes earthing the SWA armour at the outbuilding side, yet also mentions nothing about earthing the armour at the house C/U side, all he mentions is to earth the outbuilding via an earth rod.

I have always found this very confusing. Should the armour or earth core be earthed at the house side, or should the SWA armour or earth core be earthed at the outbuilding side?

Why not put it to the non rcd side and use a rcbo & do away with the rcd outlet, that way cable is covered & the outlet meets regs with regards to rcd protection, plus solves your descrimination problem.

Cheers for your positive responses.

I have put feed from C/U on non RCD protected side of C/U fed through the wall directly to an RCD spur that sits on the outside wall of the house. I thus achieve protection tof he internal "feed" portion of the circuit as it is enclosed in the wall & behind plaster etc, with the external SWA to the 13amp socket and the socket itself protected in it's entirety by the RCD spur. Problem solved with regards to discrimination & protection of outside portions of circuit & earthing.

Much appreciated your responses.

Ta

Brandt16