Hello all,
Please go easy, I have never used a forum before but this scenario has me stumped, having searched online for potential answers for some weeks and my electrician seemingly equally confused.
Some time ago I got an electrician to replace the consumer unit, from a rewireable fuse type. The layout of the new board (all BG products) is each of the 6 circuits connected through a 1 pole RCBO with a main isolating switch covering all circuits. Everything seemed to be ok when it was fitted with the electrician completing all his checks without there being any issues.
However, the garage socket (a single socket on a circuit all of its own, total length of cable 1m from the consumer unit with 16A RCBO) would regularly trip, even with double insulated items with no earth connection in the plug. Every one of the items which caused the garage circuit to trip would always work without issue when powered from any of the sockets in the house on a separate circuit (through exactly the same type of RCBO). After a short period of time the RCBO would no longer reset at all, even with nothing plugged into the circuit.
The electrician returned and fitted a new replacement RCBO and this also would regularly trip. So, we decided to replace the garage socket and short length of cable to eliminate any issues with the circuit, but it would still trip (new circuit is 1m of 2.5mm cable and 2 x double sockets). The electrician then fitted a slightly older RCBO (same make and specification but just a slightly older model) and it seemed to work. But every so often it would still trip, particularly if using a power tool and not allowing it to fully come to a stop before restarting, and now again the RCBO will not reset at all.
I am generally a competent DIYer and a professional engineer who can work through most problems logically, but my electrical understanding is at a very basic level. At present with the still broken RCBO fitted and remaining in the open position I have measured that there is a 50 Ohm resistance between the neutral and live on the garage circuit, but if I remove one of the wires from the RCBO there is an 'infinite' resistance (the same as all the other circuits). This would suggest that the broken RCBO is somehow connecting the L and N. The RCBO will not stay set even with the wires removed from its L and N out terminals so this suggests to me that the RCBO is broken and in need of replacement.
A further observation is that some fairly non-scientific experiments conducted before the RCBO stopped resetting showed that if I connected a radio to the circuit and put it on quite loud then the RCBO was less likely to trip.
Rather than having to replace the RCBO every few months and have to regularly reset it I would like to try and resolve the underlying cause of the frequent tripping.
My questions are:
Does anyone have any idea what might be causing the RCBO to continually trip when a load, of over circa 400W, is applied?
Has anyone else had problems with RCBO's when supplying only a single relatively large load?
Are there any other basic checks or tests that I can conduct to try and get to the bottom of the problem?
Many thanks for taking the time to read my essay, and I would be pleased to hear your views. Let me know if any further information would help in offering suggested answers.
Please go easy, I have never used a forum before but this scenario has me stumped, having searched online for potential answers for some weeks and my electrician seemingly equally confused.
Some time ago I got an electrician to replace the consumer unit, from a rewireable fuse type. The layout of the new board (all BG products) is each of the 6 circuits connected through a 1 pole RCBO with a main isolating switch covering all circuits. Everything seemed to be ok when it was fitted with the electrician completing all his checks without there being any issues.
However, the garage socket (a single socket on a circuit all of its own, total length of cable 1m from the consumer unit with 16A RCBO) would regularly trip, even with double insulated items with no earth connection in the plug. Every one of the items which caused the garage circuit to trip would always work without issue when powered from any of the sockets in the house on a separate circuit (through exactly the same type of RCBO). After a short period of time the RCBO would no longer reset at all, even with nothing plugged into the circuit.
The electrician returned and fitted a new replacement RCBO and this also would regularly trip. So, we decided to replace the garage socket and short length of cable to eliminate any issues with the circuit, but it would still trip (new circuit is 1m of 2.5mm cable and 2 x double sockets). The electrician then fitted a slightly older RCBO (same make and specification but just a slightly older model) and it seemed to work. But every so often it would still trip, particularly if using a power tool and not allowing it to fully come to a stop before restarting, and now again the RCBO will not reset at all.
I am generally a competent DIYer and a professional engineer who can work through most problems logically, but my electrical understanding is at a very basic level. At present with the still broken RCBO fitted and remaining in the open position I have measured that there is a 50 Ohm resistance between the neutral and live on the garage circuit, but if I remove one of the wires from the RCBO there is an 'infinite' resistance (the same as all the other circuits). This would suggest that the broken RCBO is somehow connecting the L and N. The RCBO will not stay set even with the wires removed from its L and N out terminals so this suggests to me that the RCBO is broken and in need of replacement.
A further observation is that some fairly non-scientific experiments conducted before the RCBO stopped resetting showed that if I connected a radio to the circuit and put it on quite loud then the RCBO was less likely to trip.
Rather than having to replace the RCBO every few months and have to regularly reset it I would like to try and resolve the underlying cause of the frequent tripping.
My questions are:
Does anyone have any idea what might be causing the RCBO to continually trip when a load, of over circa 400W, is applied?
Has anyone else had problems with RCBO's when supplying only a single relatively large load?
Are there any other basic checks or tests that I can conduct to try and get to the bottom of the problem?
Many thanks for taking the time to read my essay, and I would be pleased to hear your views. Let me know if any further information would help in offering suggested answers.