Aircon power trip

There are generally 3 types of power tripping:

1) It trips the ELCB (Earth Leak Circuit Breaker) or the RCCB (Residual Current Circuit Breaker).

That’s the big circuit breaker with the blue lever. It is often installed on the left, the first one. It will be written ELCB or RCCB. If you are interested in what’s the difference between this two, there’s this answered question in Yahoo Answers!

earth leak circuit breaker ELCB
ELCB earth leak circuit breaker

ELCB & RCCB respectively.

If it trips the ELCB or RCCB, it’s really no good news. It means that there is a short circuit. If it is caused by turning on the air conditioner, usually, it is due to a shorted out compressor.


To reset the ELCB, you’ll need to isolate the faulty short circuited component first. Push down all the MCB first, then you’ll be able to lift up the ELCB. Lift up the MCB one at a time. Once it trips the ELCB again, that corresponding MCB is the shorted out source. Keep that MCB down, lift up the ELCB and lift up the rest of the MCB. Those appliance(s) in you house that is now without power supply is the source of the shorted circuitry.

2) It trips the MCB

On the MCB, there will be a number. The number represents the current rating. Most HDB approved air conditioner for use in Singapore hardly exceed 12 amperes (running amperes). But MCBs are usually fitted larger to accommodate for surges during start-up. Usually, a 16A – 20A MCB is installed for air conditioner use.

If it trips the MCB, your air conditioner is drawing very high current, either during start up (thus, check the starting capacitor) or gradually increases after some time. Need to check the gas pressure, are you over charging it? A dirty condenser can draw high current too. It can also be a result of the condenser fan. If it spins too slowly, it cannot effectively cool down the condenser and that will cause pressure build up, thus high ampere.

3) It trips the MAIN circuit breaker (outside of the apartment)

This kind of tripping is usually associated with a loud bang and that will probably worry many people. It must be something serious and yes indeed, it is very serious. The LIVE wire had short circuited with the NEUTRAL cable.

Fortunately, this problem may turn out to be a small problem. How does live wire short circuit with the neutral cable?

electric cable joined and insulated using electrical tape.

This problem is often caused by poor workmanship. When electrical cable is not long enough, they could have been joint together by twisting the cables together and insulating those using tape as seen on picture above. This is a common practice for “electricians”.

Nevertheless, one must understand that such joints must be waterproof when used in an air conditioning system. This is because these cables are often placed inside the PVC casing together with the copper pipes and condensate water pipe.

When the system is new, things works pretty fine. But as the system becomes old, the inside of the PVC casing may become wet as the copper pipe insulation degrades. The electrical tape that were used to insulate the electrical cable may become lose too. Once water creeps between the cables, it will cause the power to trip, often with a loud bang. 

Follow the “bang” and open up the casing, repair the damaged cable and insulate the cables properly.

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