Sporadic tripping of Residual Current Circuit Breaker (RCCB) /Earth Leakage Circuit Breaker (ELCB)

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csubhas

Joined May 14, 2021
1
Subject: Sporadic tripping of Residual Current Circuit Breaker (RCCB) /Earth Leakage Circuit Breaker (ELCB).
I am an electrical engineer myself and am facing an unexplainable technical issue at my residence. The complete electrical wiring (input 220V, 50HZ, single phase) at home has been carried out by separating the power consuming circuits powering Air conditioner, refrigerator, washing machine, microwave, pump etc. from the light power consumers like lights, fans, 5A sockets etc. The power circuits have their own adequately rated single pole Miniature circuit breakers (MCBs) protected by a RCCB/ELCB, 63 A, 2 pole with fault leakage current of 300 mA whereas the light power circuits have their own MCBs and another ELCB with leakage current 30 mA.
Since some days the power circuit ELCB, 300mA is tripping although all the MCBS remain in ON position. It is possible to reset the ELCB immediately until it happens again sometimes after 2-3 days or even a few hours. I have tried to trace the problem by physically disconnecting (pulling the plugs out) the loads one by one. I could not come to any conclusion and the tripping continues to happen sporadically. The light power circuits have no such problems with the 30mA ELCB remaining ON always.
To rule out any problem with the ELCB itself, I replaced it with a new one but the problem persists.
The wiring in my house is 35 years old. Will wiring insulation deterioration over a period of time cause this malfunction?
Any technical solutions????
 
Do you have an Oscilloscope?

Around 5 years ago I was involved in a case study where a factory replaced their complete light system with some cheap Chinese, dimmable led lights. The drivers were so bad that the pf and THD became truly horrible. The circuit breaker would trip.

However, based on what you mentioned: I suggest just replacing that circuit breaker. They do deteriorate over time.

If that solves the problem, consider replacing all of them preventively as well.
 

Ian0

Joined Aug 7, 2020
2,252
Do you have an Oscilloscope?

Around 5 years ago I was involved in a case study where a factory replaced their complete light system with some cheap Chinese, dimmable led lights. The drivers were so bad that the pf and THD became truly horrible. The circuit breaker would trip.

However, based on what you mentioned: I suggest just replacing that circuit breaker. They do deteriorate over time.

If that solves the problem, consider replacing all of them preventively as well.
The TS said that he had already replaced his RCCB and that the fault was not on the lighting circuit.

British regulations require a 30mA RCCB originally on any sockets that could be used for equipment outdoors, but now on all sockets, and they rarely cause a problem with nuisance tripping. 300mA is a lot of fault current. Either a certain piece of equipment has a problem, or there is some deterioration of the cables: are there cables outside where water could get in or sunlight could cause the insulation to become brittle, or could it be rodent damage?
 

Yaakov

Joined Jan 27, 2019
3,161
A megohm meter can help locate faults due to poor insulation. Jordan from Artisan Electrics makes some very good videos. This one might not be the ideal for your problem, but there are many and it will certainly give you an idea...

 

Ian0

Joined Aug 7, 2020
2,252
A megohm meter can help locate faults due to poor insulation. Jordan from Artisan Electrics makes some very good videos. This one might not be the ideal for your problem, but there are many and it will certainly give you an idea...

You need one which will test at 500V, like the good old hand-cranked Megger. It is most likely that the insulation is breaking down. Testing at the usual 3V output from a multimeter even if it has a 10M resistance range might not show up the fault.
 

Yaakov

Joined Jan 27, 2019
3,161
You need one which will test at 500V, like the good old hand-cranked Megger. It is most likely that the insulation is breaking down. Testing at the usual 3V output from a multimeter even if it has a 10M resistance range might not show up the fault.
Yes, the purpose built instruments for testing house wiring are now available for surprisingly low prices on Amazon, eBay, and Ali Express.

As an aside, if I was in the UK and needed an electrician, I wouldn’t hesitate to call Artisan Electrics. Their YouTube channel is a great advertisement. I gather they are hard to book being in heavy demand.
 

Dodgydave

Joined Jun 22, 2012
9,954
With Rcd tripping faults i always start by measuring the currents in the Earth wires on the circuits on that Rcd, then if you can't see any reason, and the fault persists randomly, i remove the earth's on these temporarily one at a time to narrow it down .
 
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