Making "good" an existing garden "installation"

[Soulcraft Electric]

Neighbours, eh, who'd have 'em?

I was asked to investigate why a neighbour's garden "installation" was faulty and being neighbourly agreed to take a look. It was clear that the neighbour expected (required) that only remedial action to be taken... I've documented the initial state and the remedial work carried out.

My question is specifically around testing and is at the end of the post.

Existing installation
2 spurs had been taken off the downstairs ring final circuit through the outside wall of the property. At the origin of each spur a PowerBreaker RCD Fused Spur (Passive) - 30mA (PowerBreaker RCD Fused Spur - http://www.greenbrook.co.uk/fused-spurs-powerbreaker-rcd-fused-spur-passive-30ma-1468) had been fitted. These were used as "switches". Each spur had been run in 2.5mm T&E "protected" by flexible PVC conduit buried under a patio (depth unknown) and then continuing under a raised bed (again, depth unknown).

Spur "A"
Fed a single single weatherproof socket before continuing to a weatherproof junction box where the 2.5mm T&E was connected to 4mm 3 core SWA via a terminal strip. The SWA had then been buried before exiting the ground a metre before a decking area. The SWA then fed a series of post lights (IP23 rated) which had been installed on the decking.

Condition of Spur "A"
- 2.5mm T&E -> 4mm SWA
- Weatherproof socket showed clear signs of water ingress
- Weatherproof junction box cover was missing exposing terminal strip
- SWA appeared to be glanded correctly at the origin (junction box) but glanding at decking unknown (junction box(es) inaccessible beneath decking)
- Post lights showed clear signs of water ingress

Spur "B"
Fed a single single weatherproof socket before continuing to a first weatherproof junction box where the 2.5mm T&E was connected to 4mm 3 core SWA via a terminal strip. The SWA had then been buried before exiting the ground a metre before a decking area. The SWA then fed a second single weatherproof socket attached to the deck.

Condition of Spur "B"
- 2.5mm T&E -> 4mm SWA.
- First weatherproof socket showed clear signs of water ingress.
- Weatherproof junction box cover was missing exposing terminal strip.
- SWA not glanded at second weatherproof socket.

Initial tests
- continuity - r1, r2, rn satisfactory on both spurs.
- insulation resistance - spur "A" < 20 MOhm, spur "B" > 500 MOhm (just the spur "runs").

Remedial action

Spur "A"
- Replaced faulty PowerBreaker RCD Fused Spur.
- Weatherproof socket replaced, Wiska box and Qinetic wireless switch fitted. Wago connections.
- Wiska box and Qinetic wireless switch fitted. SWA glanded. Wago connections.
- Post lights dismantled and terminal strips replaced with Wiska Shellboxes and Wagos connections.

Spur "B"
- Replaced faulty PowerBreaker RCD Fused Spur.
- First weatherproof socket replaced, Wiska box and Qinetic wireless switch fitted. Wago connections.
- Wiska box and Qinetic wireless switch fitted. SWA glanded. Wago connections.
- Second weatherproof socket replaced, Wiska box and Qinetic wireless switch fitted. Wago connections.

Finally, my question! Clearly, the circuit that has been altered is the downstairs ring final circuit. In order to conduct an insulation resistance test I will need to bypass the Powerbreaker units. The other issue is the age of the neighbours... They've already told me that they're not sure what loads are connected and where! An MEIWC requires test results for L-E, L-N, and N-E.

If the test is made with the Line and Neutral conductors connected together and earth, is it acceptable to use that value for all 3?

Thanks!

 

[Octopus]

I would test the outside parts from where they spur off the socket circuit and state this on your MWC.....

I am not a fan of testing L&E to earth - especially on outdoor circuits and yes you need to bypass any RCD's

 

[Soulcraft Electric]

Thanks. That’s what I was hoping .

The lack of definitive advice on completion of both EICs and MWCs where there are vagueries isn’t entirely helpful IMO.

 

[Octopus]

your planned work isn't installing - its making good ........... and this is where BS 7671 isn't very helpful as what you are planning is "maintenance"

documenting the tests etc is a sensible course of action as we all know garden installation do fail and some on a very regular basis

The only thing I would recommend is that you check the spurs off the ring are DP isolation ................

 

[johnduffell]

IR testing L-N at 250v should at least indicate whether there are loads still if I'm not missing something. But finding and disconnecting might require splitting things up.

 

[Soulcraft Electric]

your planned work isn't installing - its making good ........... and this is where BS 7671 isn't very helpful as what you are planning is "maintenance"

documenting the tests etc is a sensible course of action as we all know garden installation do fail and some on a very regular basis

The only thing I would recommend is that you check the spurs off the ring are DP isolation ................

The Powerbreakers are indeed DP

 

[HandySparks]

- Replaced faulty PowerBreaker RCD Fused Spur.

What was wrong with both the original RCD fused spurs?

Finally, my question! Clearly, the circuit that has been altered is the downstairs ring final circuit. In order to conduct an insulation resistance test I will need to bypass the Powerbreaker units. ... An MEIWC requires test results for L-E, L-N, and N-E.

If the test is made with the Line and Neutral conductors connected together and earth, is it acceptable to use that value for all 3?

For this sort of remedial work, I would test only the work I have done (unless it's easier to test the whole circuit).

Where I have just replaced accessories, light fittings, etc., I don't feel that it is necessary to fill in every box on the cert. I'll typically measure the Zs and RCD timings, plus any other tests that I feel necessary.

If you haven't taken a measurement, you can't fill in the box. Don't make things up!

...The other issue is the age of the neighbours... They've already told me that they're not sure what loads are connected and where!

Most customers don't know what's connected to a particular circuit.

I would test the outside parts from where they spur off the socket circuit and state this on your MWC.....

Agreed.

I am not a fan of testing L&E to earth - especially on outdoor circuits and yes you need to bypass any RCD's

I'm perfectly happy to test L+N to E if the time taken to disconnect and reconnect RCDs and loads is disproportionate to any additional measure of safety. Obviously, on a new circuit or an additional part to a circuit, the full range of tests is easy to do, because you can test before connecting.

 

[Octopus]

Back to the OP ........... what is actually wrong with this installation? Is the customer suffering from RCD tripping?

Does the house have RCD protection on the socket circuit the spurs are run from?

 

[Soulcraft Electric]

Both Powerbreakers were defunct: both test buttons were ineffective. I replaced both. The ring final circuit does not have RCD protection.