RCCB nuisance tripping is notoriously difficult to diagnose. The RCCB is essentially looking for current imbalance between Line and Neutral. If there is an imbalance, it mostly likely means the residual current is flowing through a faulty equipment or worse through a human. When the difference current exceeds beyond the set threshold of 30mA(in this case) it should trip and disconnect both line and neutral conductors.
The tricky part here is that all equipments with a ground pin can have a leakage to earth. This may be well below the set threshold of 30mA. But if you add up all the equipments in the house, it can exceed the threshold and start tripping the RCCB, But this is typically very rare if all appliances are in good working order.
Trying to isolate by switching off different MCB's in the house is not fool proof because, it only identifies if the leakage is from line to earth. Not neutral to earth. Note that neutral can be several volts above earth especially in apartments where it can be a long distance to the transformer where neutral get connected to Earth. The neutral voltage varies based on how many houses are sharing the return wire and how much load is put on the wire.
Adding another complication to this is that residual current is not stable. It varies depending on how appliances are being used. So it can be hard to re-create the fault consistently.
The ideal way to diagnose would be to get a sensitive clamp meter which can measure currents down to ~1mA and isolate both line and neutral and test each circuit in the house.
I ran into the same issue last year and was not able to identify the root cause. Unqualified local electricians will try to blame it on the RCCB and if it still trips with a new one, suggest bypassing RCCB which is absolutely not recommended.
I had bypassed the RCCB for a while and a year later with few appliances swapped, the issue has disappeared in my case.
Another potential cause could be leakage due to old wires with worn insulation in the electrical conduits. This is very difficult to identify unless we pull out all the wiring and check and can turn out to be expensive.
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Originally Posted by Rodie09 Recent Work:
I got some additional points done 3-4 months back, mostly LED decor lights ranging from 2 watts to 18 watts. This required some new concealed wiring also but considering low load it was not done in proper conduits. Mostly just a phase and neutral wire for these small lights in a flexi tube. I am sure many of us must have done similar. |
Inspect every part of the new wiring and verify that either the Line or neutral does not come in contact with any metal building structural elements (eg Rebar, Metal containers behind switch boards, bulb holders etc). These are typically earthed and any leakage from neutral through these can trip the RCCB.
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Originally Posted by Rodie09 DP Box - Located right after main entrance this houses about 18 Havells circuit breakers for different circuits in house and 1 Havells RCCB of 63 A/30 mA which is standard in apartments. Issue:
A week back the RCCB tripped. None of the breakers opened but just the RCCB was down. I isolated all breakers and tested one by one and found this to be happening from master bath 25 litre Racold geyser. I thought I had found the issue. Disconnected the geyser. |
My educated guess here would be a high impedance (Meaning not a 0ohm short) leakage from neutral to earth. When there are not many appliances switched on, the neutral-earth voltage will be low and the leakage current will be below the RCCB threshold. As the appliances are turned on the return current on the neutral increases which in-turn increases the neutral-earth voltage and increasing the leakage current tripping the RCCB.
Suggested experiment if you are up for it and have an electrician who can follow instructions
1. Disconnect every appliance in your house with an earth connection.
2. Disconnect and Isolate the neutral for all circuits which is typically shorted at the breaker box.
3. Connect a single circuit to the mains/RCCB and add enough load.
4. Repeat on each circuit until you find the one circuit which causes the RCCB to trip consistently.