ELECTRICAL VOLUNTEERS REPORT SUNDAY 10th JULY 2016

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JONATHAN-BARNES
Posts: 32
Joined: Sat Nov 29, 2008 2:35 pm

ELECTRICAL VOLUNTEERS REPORT SUNDAY 10th JULY 2016

Post by JONATHAN-BARNES »

Today it was me, Alan and Clive. We tested the fire alarms as usual.

Today’s job was replacing the two outdoor flood lights just below the roof of the Standard 4 shed, one on the North end of the shed and one on the South end. The lights illuminate the official walk way and are controlled by a photo cell unit at the South end. The lights have been out of action for a long time. It has been decided to replace them with LED floodlights as they consume less energy than the halogen lamps.

First we went to the South end. The old lamp had been taken down a couple of weeks ago. The end of the pyro cable needed a new termination so this was fitted. We then switched on to do some testing. As we switched on, the main RCD in the distribution board tripped out and all the lights and power went off, indicating an earthing fault. We switched the circuit off and reset the RCD. It took us some time to trace the fault. We first thought it may have been caused by the old light fitting at the North end so this was taken down and the circuit re tested. The fault persisted.

After some time it was found that the fault was within the length of pyro cable that feeds the south end light. Pyro cable consists of a copper sheath with copper conductors running through the middle. The conductors are insulated from each other and from the sheath by magnesium oxide powder. This is an excellent insulator when dry. Unfortunately, the powder is hygroscopic. If the copper sheath is damaged anywhere along the length of the cable, the powder absorbs moisture from the atmosphere and the insulation resistance is reduced causing an earth leakage fault.

We isolated the faulty cable and decided to do some rewiring, on the inside of the building, high up near the ceiling where we could use PVC cable instead of pyro. This proved to be satisfactory. We then replaced the flood light on the North end of the building. We also re- terminated the pyro that feeds it. The system was tested and found to be OK.

Whilst we has the long ladder out, we also replaced a couple of 5 foot light tubes inside the building.

The weather did not help today as we had to keep running for cover during frequent heavy showers.

Thanks to the Standard 4 volunteers for their cooperation as we kept plunging them into and out of darkness all day.
RichardErnill
Posts: 226
Joined: Wed Nov 18, 2009 4:23 pm
Location: Timperley

Re: ELECTRICAL VOLUNTEERS REPORT SUNDAY 10th JULY 2016

Post by RichardErnill »

Good grief no cake since June 12th...how are you managing? :lol:
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