Lately, during thunderstorm my condo elcb trips (main breaker). i.e. whole house no electricity.

This happened after I changed new aircond, but the thing is it is using back old wiring.

Any idea what could cause this? previously mcb trip (small breaker) due to upstairs leaking water to my light but that has been solved.

First time encounter this issue in condo as normally condo wont trip during lightning.

ELCB or main incoming MCCB tripped? Different device tripping will signifies different issue.

For the ELCB, if tripped , it is associated with the earth fault . You will not be able to switch back the ELCB until the fault have been rectified. Possible fault may occured if the wires short circuited/ insulation damaged, water contact , equipment fault, melted cable due to overheating/ undersized cable , etc.

If MCCB tripped, it is associated with the over current / sudden surge of current . The lightning may be one of the cause or it can also signifies that your unit is drawing the power until there is no more buffer of safety, any small fluctuation (up surge) will cause the incoming current to exceed the MCCB rating & leads to tripping.

possibly the aircond got leak
i hope the installer use dual pole switch (like water heater switch) for your aircond.

then just switch off the new aircond switch. and observe.

if not, when the electrician come, ask them to change for you

It’s elcb. The one with the test button. But only trip when got lightning.

The new AC unit is fully inverter ? The AC is in operation during the lightning / trip event?

Standard unit. Aircond not on but switch for aircond on 24/7

I have higher tendency to believe it is due to leakage / fault level from the AC unit if such is the case. You can totally isolate the power of the MCB to this unit in future when there is lightning, observe if the ELCB still trip. If the ELCB not tripping after the isolation of the power to this AC , you can pin point the issue to the AC unit. If it still trip, it is not the AC .

The reason I asked if the AC is inverter or not because for the inverter unit, there is frequency modulation to the compressor . Whenever there is the frequency modulation , the harmonic distortion will increases & may contribute to nuisance tripping.

Mana ada ELCB. There’s no earth connected to it

I have a feeling installer for new aircond hit some cables when drilling for new mounting plate.

But on the other hand if cable injured, it should have tripped when hit.

So far only happens when there is thunder which is really odd for a condo.

ada lahhh

try change to RCCB, suspect your MCCB or whatever already too old and sensitive

You can safely eliminate this possibility. If there is fault, no way you can switch back the protection relay until the fault is rectified.

The more troublesome one will be the transient fault and this transient fault level got something to do with your AC unit.

Its RCCB/RCD, functional concept is incoming L amps = outgoing N amps + acceptable tolerance of losses (to resistance); there is nothing connected on the Earth

I have turned off aircond switch and it still trips during thunderstorms. Really scratch head. At the moment I am in genting. I know tripped cause read on news there is thunderstorm in kv and my cctv not working.

Could extension plug connected to another extension plug cause this? I am using double extension for my fish tanks.

This post has been edited by jason1986: May 4 2023, 09:00 PM

It means, the trip is not due to the new AC unit, it is something else.

You many not be able to eliminate possibility of double extension until you try to isolate the case during the thunderstorm.

The last few days lightning during evening were bad.

Your RCD pic? Got cheap ones w/o anti nuisance trip and that’s probably why u kena so many nuisance trips

Kozuka brand. Previously no such issue though. Just happening lately. I just bought a maxguard one to try and swap and see if it solves the problem

If it's condo then most likely it's leakage to ground with high resistance as your normal peak usage doesn't induce high enough leakage current to trip the RCCB. Could be wet damaged wire insulation or neutral wire get damaged by mounting stud/bolt/screw and leak directly to concrete and not via earth wiring. Get experience electrician that know use the right tools (leakage current clamp meter + insulation tester) to troubleshoot this. There is 1 infamous kiasu self-proclaimed "electrical expert" that don't know how to make use of his tools (ground/leakage clamp meter & multifunction tester) except flaunting it when troubleshoot RCCB tripping, and still have the audacity to charge half assed inspection 600+.


If for some reason you unable to replace the wiring and just repair the damaged insulation, you can try isolate the circuit into it's own 16A/20A RCBO and not downstream of your existing RCCB.