Complex carport lights

[Andrew_van_Zyl]

Called out to investigate why several rows of carport lights are not working.

The complex is 9 years old and electrical installations seems good (judging by the use of ferrules used for circuit breaker connections)

The CB trips, but not immediately, after switching on. No earth leakage. Continuity between live and earth when tested at the DB

My approach was to try and isolate the short by disconnecting sections of the circuit (each carport) and testing if the short was downstream or upstream of the disconnection.

I've pretty much disconnected everything but the CB still trips meaning there is more to this circuit that what I have seen.

I've taken a 60m trail lead to test continuity between the live at the DB and where I think the circuit begins, but am not finding it.

I've also taken out the LED tubes in the light fittings in case one of them has been inserted the wrong way round - had this on a previous site.

Any suggestions from the old hands?

[Jaws]

Called out to investigate why several rows of carport lights are not working.

The complex is 9 years old and electrical installations seems good (judging by the use of ferrules used for circuit breaker connections)

The CB trips, but not immediately, after switching on. No earth leakage. Continuity between live and earth when tested at the DB

My approach was to try and isolate the short by disconnecting sections of the circuit (each carport) and testing if the short was downstream or upstream of the disconnection.

I've pretty much disconnected everything but the CB still trips meaning there is more to this circuit that what I have seen.

I've taken a 60m trail lead to test continuity between the live at the DB and where I think the circuit begins, but am not finding it.

I've also taken out the LED tubes in the light fittings in case one of them has been inserted the wrong way round - had this on a previous site.

Any suggestions from the old hands?

Have you measured the actual current draw ? Could be a faulty circuit breaker. Next would be to do insulation resistance test on the conductors.

[Andrew_van_Zyl]

Thanks Jaws. Current draw before tripping is 38A (it's a 10A breaker)
I'm working through this one - the circuit has several sub-circuits feeding rows of townhouses so I started at the beginning, isolated the feed to the next rown, connected that rows lights and worked my way down. I've cornered the issue at the last row (it would be!) so need to go back and check it out.

[Andrew_van_Zyl]

Quick update - issue turned out to be improper cable joins on Norsk cable.



There is a lesson in this perhaps. The complex has over 200 units supplied by 3 transformers and supply kiosks. Carports lights 1 to 84 would trip the 20A circuit breaker.

I had absolutely no idea where to start. I isolated sections of the circuit - up and down from the main road, removed the LED tubes and then Meggered them. If the section failed I then went carport to carport, isolating where the junction box sent cable into the ground and where it came back out of the ground.

It was very clear which underground sections failed. Luckily the Norsk was just under the pavers and to my great relief, we found MANY failed cable joins. I laid new Norsk and replaced the round junction boxes with IP65 boxes, and slowly we restored power.

Why Renico would join bits of 1.5mm Norsk underground escapes me. Cash strapped subcontractor comes to mind...

We are almost there. Lifting and replacing paving is a pain in the @ss - it needs more labour than I thought.

End of the day the client is happy. We are fortunate to have a Trustee with an engineering/mining background so the snails pace of progress is understandable to him.

Lesson learned - trust your Megger and break the problem down into manageable bits that make sense.

Still beats my old corporate job hands down!!!