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M

mdgibbs32

Hi All
I have a prob i hope someone has come across
clients RCD is tripping at odd times. Doest seem to be any pattern or any specific piece of equipment causing it. Not one particular circuit either...trips on downstairs ring, upstairs ring, lightings ...you name it.
Wont reset until all mcbs are off, then switch mcbs back on individualy. Sometimes will be fine, sometimes an mcb will trip it (never same mcb twice)...do it all again and rcd is fine.

tested all circuits insulation test, all ok.

Im lost, only thing i can think of is the actual RCD is "twitchy" but ive never come across that before.
Any ideas anyone ?
 
Try the ramp test at the RCD with no loads connected and note the reading. Then turn all circuits and loads on then redo ramp test. The difference between the 2 readings will be the approximate earth leakage on the loads. Remember a 30mA RCD can trip at anything >15mA.
 
I had a faulty RCD a while back that had been playing havoc. Tripped at random and occasionally wouldn't reset with a load connected.

Worked out it was a faulty unit when I did an RCD auto test about 5 times and got varying results.
 
Try the ramp test at the RCD with no loads connected and note the reading. Then turn all circuits and loads on then redo ramp test. The difference between the 2 readings will be the approximate earth leakage on the loads. Remember a 30mA RCD can trip at anything >15mA.

got to agree with this for probable cause
 
Try the ramp test at the RCD with no loads connected and note the reading. Then turn all circuits and loads on then redo ramp test. The difference between the 2 readings will be the approximate earth leakage on the loads. Remember a 30mA RCD can trip at anything >15mA.

sorry sintra just making sure i understood this properly... ramp rest at the rcd...reconnect circuits and mcbs, then ramp test again at the rcd...have i git that right ?
 
sorry sintra just making sure i understood this properly... ramp rest at the rcd...reconnect circuits and mcbs, then ramp test again at the rcd...have i git that right ?

That's basically right. If you're getting a lot of earth leakage then you may well have found the cause of the RCD tripping. The next job will be tracing where the leakage is coming from! I had a job once where the leakage was around 20mA all the time. The RCD seemed to be teetering on the edge of tripping all the time, and intermittently would operate, seemingly at random. It turned out to be a crushed line and CPC at a DIY-installed spur off a spur in the loft. Took me ages to find the fault, mainly because the homeowner didn't even know that socket was there, and it was hidden under a load of crap that had been dumped in the loft!

You can still hope it's just a faulty RCD though.
 
That's basically right. If you're getting a lot of earth leakage then you may well have found the cause of the RCD tripping. The next job will be tracing where the leakage is coming from! I had a job once where the leakage was around 20mA all the time. The RCD seemed to be teetering on the edge of tripping all the time, and intermittently would operate, seemingly at random. It turned out to be a crushed line and CPC at a DIY-installed spur off a spur in the loft. Took me ages to find the fault, mainly because the homeowner didn't even know that socket was there, and it was hidden under a load of crap that had been dumped in the loft!

You can still hope it's just a faulty RCD though.

Dont you just love them jobs......:)
 

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