Main Breaker Gets tripped every 1-2 hours but last longer in the night

Question

Our home is located in India. We have an individual circuit breakers for all the 7 rooms in our home. And wrapping them whole is the main breaker. Earlier there used to be short circuit in certain rooms due to water leakage. When short-circuit occurred, everything thing else worked if turned of the individual breaker corresponding to that branch where short-circuit originated. But now we have a different problem.

Even after switching off all the individual circuit breakers corresponding to each branch, the main breaker is getting tripped. Electrician told us that it was due to ground-fault. He opened up a few switch boxes and found out that termite had eaten some portions of the wire, which resulted in neutral wire coming in contact with the ground wire. They identified 3-4 switch boxes and we completely rewired it. Even ceiling fans were given extra rubber bushes at the support. But after a week since they left, the issue is persisting. Earlier, where the ground-fault problem was identified, the main breaker used to never turn on even when the individual circuit breakers were turned off. Now, the same issue persists but now we get 1-2 hours of electricity before the main breaker trips.

One another observation I have made in the current scenario is that, if I try to switch on the main breaker right after it got turned off with all the circuit breaks in off mode, it will get tripped right away. But if I do it after 10-15 minutes, it stay on for another 1-2 hours. And in the night, if we are lucky, we get 5-6 hours gap before it gets tripped!

I would be glad if somebody can help to put possible reasons why this is occurring. We had already brought in electrician 3 times already!

Edit: I turned all the knobs to phase 2 and it is working okay for the past one week. What could be the possible reason that it doesn't work in Phase 1 and 3?

Here is quick picture of our electricity distribution panel with the individual circuit breaker and main breaker:

Answer 1

When an appliance has an internal shorting or arcing fault, or electrical wiring has is shorting hot or neutral to ground, that is called a "ground fault".

You have a "Whole-house RCD" - aka GFCI - it looks for current leakage from ground faults. SOP in Europe-influenced electrical installations is to fit a 30-35ma (milliamp) RCD that protects the whole house. The goal is to protect the house from arcing fires; 30ma can kill you. This unit is typically combined with the main circuit breaker.

Beyond the whole-house RCD, you then have branch circuits with circuit breakers. Most of them will be one size such as 13 amp or 16 amp. Take note of that.

North American practice is to protect each branch circuit with its own GFCI (RCD) device (breaker). The goal here is personnel protection, so only bathrooms, kitchens etc., and a lower detection threshold of 8ma.

My suggestion is to do the American thing - and replace one of your branch circuit breakers with an 8ma personnel-grade RCD, of the amperage rating of most of your branch circuit breakers. This will have a lower threshold than the main, so it "should" trip sooner. If the problem is on that branch, the trips will mostly now occur on this breaker. If that branch circuit is not the problem, then swap the breaker to another branch circuit, and try it again. Eventually you will narrow it to a single branch.

Then unplug all the appliances and test again. If that does not clear the problem, then disassemble all the junction boxes in that branch and look at the wiring. If unplugging the appliances does clear it, then return one appliance a day and when the problem returns, that's the one. Have the appliance serviced.

This method won't work for the few odd-sized breakers you may have for stove, water heater, air conditioning, etc. Simply switch those off for a day (when feasible) and see if the problem goes away when they are off.

Answer 2

The scenario you are describing is waiting for something bad to happened. It can easily create a fire or someone can get electrocutated. From what you are descibing it seems a ground fault is present. A ground fault occurs when an ungounded conductor ("hot wire") makes contact with a grounded "neutral" conductor or the grounding (green) conductor, but a continuos and or effective path for current to travel back and trip the breaker has been compromise. The breaker has been doing what it was made for. Eventually it will fail and you may end with catastrophic results. There are several conditions that need to be present in an electrical circuit in order for it to operate safely. Not having the big picture is just not save changing parts here or there.

Answer 3

I believe your Main Breaker is bad. If you put your hand on the main breaker does it feel abnormally hot? Better yet you can use an infrared thermometer to check it out. You can buy one for about $30. I should be reading less than 30C or 90F.

A breaker has a bimetal part that expands at different rates. so when the breaker begins to overload it heats up and warps and causes the breaker to trip. After the breaker has tripped several times this part becomes damaged and will continue to heat up and trip even if the breaker is not overloaded. That's why it doesn't reset right after it trips it needs to cool down first. This condition will continue to get worse until it won't reset at all.

Of course since we are not on the property I can't be 100% sure, but that's where I would start looking.

Hope this helps and good luck.

Answer 4

Have your electrician run an insulation test on all circuits.

Ordinary breakers only care about the current on the hot -- the neutral's assumed to be carrying the same current, so it's not going to overheat if the hot's fine barring a wiring error. However, RCDs care about the current on both hot and neutral, so if you have a neutral to ground fault somewhere in your wiring network, it will still trip the RCD even if all your branch breakers are shut off, making the fault very hard to localize in an Eurostyle master-RCD setup.

However, you can have your electrician bring to bear a power tool on this problem, namely an insulation resistance tester or "megger". At a suitable time (when all power to the unit can be turned off at the main breaker/RCD and all appliances can be unplugged/unhooked), have him take each circuit's hot and neutral and run an insulation test to ground at 500V. This should expose the failing circuit -- from there, it's simply a matter of eliminating parts of the circuit in question with further insulation resistance tests until the problem is found.