Zs reading high on external lighting

[cliffed]

Fitted 2 new external lights onto existing cabling, their on a remote wall quite a distance from house.
My mistake was not doing a Zs before I started the works.
Finished & tested Zs reading 14 ohms.
Its a Tncs supply quite a big install…the lights are supplied by a 6 amp C type MCB.
Reported this to the Client & my Boss…still no feedback on what to do.
I”ve suggested a Rcbo to protect this circuit & FI TO take place.
Windering your thoughts on this.

 

[Dave OCD]

Is this an older SWA install with the armour as the sole cpc ? If so I'd suspect corroded armour at one or more termination points.

 

[i=p/u]

As said needs a good looking at, and rcbo would temporary protect until powers that be sort out a plan. But doesn't sound good. Like for like, many would swap and walk away without testing.

 

[Pete999]

I did ask what test had been done earlier but the OP has not as yet answered.

 

[cliffed]

Is this an older SWA install with the armour as the sole cpc ? If so I'd suspect corroded armour at one or more termination points.

Yes the Swa been in some time, 2 core only,armourping used for cpc.

 

[cliffed]

I did ask what test had been done earlier but the OP has not as yet answered.

Zs test only @ present..& that was documented

 

[cliffed]

As said needs a good looking at, and rcbo would temporary protect until powers that be sort out a plan. But doesn't sound good. Like for like, many would swap and walk away without testing.

Thank you…it’s now become a major problem & who is going to pay.

 

[timhoward]

Personally I'd stick the live in the earth bar, open up a few car park lights, measure R1+R2 and form a picture of where the resistance jumps high. It shouldn't take that long to get a better understanding of what's going on.
Leaving the live in the earth bar is also an option I'd prefer to installing an RCBO. Leaving part of the circuit functional is also an option if you find good Zs for part of it, while the remainder is investigated more.
You need to talk to your boss again about this. Mistakes happen. He or she will know that.

 

[i=p/u]

Walk in turn the breaker off or remove the Live or if you have time do as tim says, find that car crash and disconnect at that point.

 

[cliffed]

Cheers everyone…lesson learnt check Zs before replacing lights.

 

[telectrix]

Yes the Swa been in some time, 2 core only,armourping used for cpc.

that is most likely the problem. as someone has already stated, corroded armour. also depends on if the SWA has been correctly glanded in the first place, not just bodged. definitley needs investigation.