Discuss Intermittent Ring fault! Any advice please. in the Electrical Forum area at ElectriciansForums.net

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Hello all, I was hoping for some advice on this ring fault I have come across. It has been intermittent for about 2 months now.

It is a converted church to a children and family centre. Installation is within 10-15 years. TN-C-S supply.

The fault is on a 32A type C RCBO 30ma which supplys 12 DSSO in dado trunking. The run is about 30-40 metres. Wired in 2.5 t+e.

The only equipment plugged in is x4 computers and x4 monitors. X2 photocopier machines and x1 shredder. All equipment is PAT tested.

It has tripped around 6 times in the past 2 months. The tests I have carried out are end to end and the values I am getting are:

r1:0.57
rn: 0.57
r2:0.69

These are fine and with figure of 8 tests comply aswell. I have then carried out IR tests which are around 45-60 meg. I have split the ring and found the incoming legs.

RCD tests pass on x1 and x5 and also ramp test is showing it trips at 25ma.

However today I tested IR again with everything disconnected and had short circuit across all conductors. I then split the ring and tested IR again on both legs and they pass. The only suspect thing is where the cables come from above the boiler room into the kitchen (behind the units) there is mouse bait and also strawberry jam used for bait however the jam looks like it follows the cables into the trunking.

The only thing I have not tried is testing for earth leakage, although I do not have the tester for that. Could anyone help by suggesting anything else I can do? Thank you!
 
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