Hi all, hope you can help me please ?
I have an outbuilding at the bottom of my garden which has a SWA cable (2 core 6mm I think but possibly 4mm) running to it which was installed when I bought my house about 10 years ago. The SWA outer wires are being used as the earth, and the cable is approximately 25m long.
I had a ground floor extension built for my disabled son around 4 years ago, and as we hadn't enough spare ways on the distribution board I had a new one fitted which is a split rail jobbie with a 30mA RCCB. Previously there was no RCCB.
Lately I have an issue with nuisance tripping of the RCCB which relates to the outbuilding - specifically where I have a particular laser printer plugged in (but not switched on) in the outbuilding. The odd thing is that if I power the printer up on the downstairs ring in the house it doesn't trip.
I disconnected everything at both ends of the SWA cable, and have meggered the cable, which gives a resistance in excess of 25MOhms between either core and the earth cores. With this printer (physically)disconnected I don't get the trips.
I guess that the printer may have a leak between L or N and earth, but why doesn't it cause the tripping when located in the house ?
Is the lack of an earth rod at the outbuilding end likely to cause this problem ? I really hope that I don't ever have to have the SWA cable replaced as it will be the mother of all nightmares routing a new one.
PS I'm an electronics engineer by trade so well aware of the dangers of electricity. Happy sorting out microprocessors etc but I'll leave the high voltage / high current stuff to you guys
Kind Regards,
Robin
I have an outbuilding at the bottom of my garden which has a SWA cable (2 core 6mm I think but possibly 4mm) running to it which was installed when I bought my house about 10 years ago. The SWA outer wires are being used as the earth, and the cable is approximately 25m long.
I had a ground floor extension built for my disabled son around 4 years ago, and as we hadn't enough spare ways on the distribution board I had a new one fitted which is a split rail jobbie with a 30mA RCCB. Previously there was no RCCB.
Lately I have an issue with nuisance tripping of the RCCB which relates to the outbuilding - specifically where I have a particular laser printer plugged in (but not switched on) in the outbuilding. The odd thing is that if I power the printer up on the downstairs ring in the house it doesn't trip.
I disconnected everything at both ends of the SWA cable, and have meggered the cable, which gives a resistance in excess of 25MOhms between either core and the earth cores. With this printer (physically)disconnected I don't get the trips.
I guess that the printer may have a leak between L or N and earth, but why doesn't it cause the tripping when located in the house ?
Is the lack of an earth rod at the outbuilding end likely to cause this problem ? I really hope that I don't ever have to have the SWA cable replaced as it will be the mother of all nightmares routing a new one.
PS I'm an electronics engineer by trade so well aware of the dangers of electricity. Happy sorting out microprocessors etc but I'll leave the high voltage / high current stuff to you guys
Kind Regards,
Robin