V
Vitesse
I got called out this evening to a tripping RCD on a TT install after a lightening strike in the area.
Its quite an old CU with mcb's and a standalone 100ma RCD on the tails between the supply and the 100A DP main switch on the board. The RCD would switch on but as soon as the CU main switch is switched on it trips the RCD.
Tested the Ra and it was 155Ω, so not brilliant but within spec for TT.
I did an IR between the CPC bar and neutral bar and found a dead short, so I disconnected all the earths from the bar and reconnected them up one by one until I found the offending circuit causing the tripping which was the ring final for the lounge. Unplugged everything, still short between Neutral and CPC on the circuit.
I split the ring and found which leg is causing the problem but it was getting late and I didn't get a chance to go any further as they had a young family they needed to be put to bed. I explained that I had to leave the offending circuit isolated on the board and locked it off so they couldn't switch it back on. I am going back tomorrow morning to split the ring further and hopefully find the problem.
I live not far away and there a massive lightening strike in the area and according to the owner it was very close to them. My only conclusion at the moment is that a voltage surge from the lightening has travelled up the earth rod, as there is no surge protection, it has somehow managed to breakdown an existing fault between neutral and cpc and has made the fault worse to the point that it is now causing the RCD to trip?
Does anyone have any more logical explanations as to what has caused this problem to appear all of a sudden?
Its quite an old CU with mcb's and a standalone 100ma RCD on the tails between the supply and the 100A DP main switch on the board. The RCD would switch on but as soon as the CU main switch is switched on it trips the RCD.
Tested the Ra and it was 155Ω, so not brilliant but within spec for TT.
I did an IR between the CPC bar and neutral bar and found a dead short, so I disconnected all the earths from the bar and reconnected them up one by one until I found the offending circuit causing the tripping which was the ring final for the lounge. Unplugged everything, still short between Neutral and CPC on the circuit.
I split the ring and found which leg is causing the problem but it was getting late and I didn't get a chance to go any further as they had a young family they needed to be put to bed. I explained that I had to leave the offending circuit isolated on the board and locked it off so they couldn't switch it back on. I am going back tomorrow morning to split the ring further and hopefully find the problem.
I live not far away and there a massive lightening strike in the area and according to the owner it was very close to them. My only conclusion at the moment is that a voltage surge from the lightening has travelled up the earth rod, as there is no surge protection, it has somehow managed to breakdown an existing fault between neutral and cpc and has made the fault worse to the point that it is now causing the RCD to trip?
Does anyone have any more logical explanations as to what has caused this problem to appear all of a sudden?