Aircon tripping power: why it happens
In an HDB flat, two kinds of breaker can cut the power. HDB's home care guide explains that the RCCB cuts off electricity in the flat when it detects an earth current leakage. An MCB protects cables and appliances from overheating: on an overcurrent from an overload or short circuit, it trips and cuts supply to its own circuit.
The Energy Market Authority (EMA) lists the causes of current leakage as ageing or exposed wires, faulty electrical appliances and damaged insulation. An aircon trip at the circuit breaker can start in the unit itself or in the wiring that feeds it.
Which breaker tripped and why it matters
Look at the distribution board (DB box) without opening any cover. EMA says the RCCB is usually in the DB box and can be identified as a switch with a "Test" button; EMA also calls it an earth leakage circuit breaker (ELCB). HDB describes the consumer unit (CU) as holding the main switch, the RCCB and the MCBs.
| What you see | Breaker that tripped | What it points to |
|---|---|---|
| The whole flat has no power | RCCB in the down position | Current leakage somewhere in the flat |
| Only the aircon circuit is off | The aircon circuit's MCB | An overload or short circuit on that circuit |
If the RCCB is the one that keeps going down, the guide on what to do when your ELCB keeps tripping covers leakage in more detail. You can also find power trip electricians in the directory.
Overload and the electrical rating
An MCB trips on overload, so the flat's electrical rating matters. HDB's aircon installation guidelines say that before installing, the owner and installer must check that the total running current of the condensing units does not exceed the approved electrical rating. In flats with a 30 amp main switch, a new 15A power point or 20A isolator for the aircon needs an electrical permit. Flats with a 40 amp main switch, or flats upgraded under the Main Upgrading Programme (MUP) or the Home Improvement Programme (HIP), need no permit.
The Consumer Product Safety Office (CPSO) notes that the 15A Type M plug is generally used by energy-intensive appliances such as air-conditioners, and that 15A socket outlets should only be installed by qualified electrical workers.
If units have been added, ask the installer or an LEW whether the total running current is still within the approved rating.
Faults inside the aircon
A fault inside the unit, for example in the compressor, the fan or its wiring, can also trip the power. Only a technician can diagnose it, so leave the aircon off until it has been checked.
FROM THE HOMEZYPRO DIRECTORY
Published aircon repair and inspection rates
For the most common unit (per job), the lowest published rates from 11 companies run from S$40 to S$100. Each figure is one company's own advertised rate with its conditions, not a market average or a quote.
See 21 published repair or inspection rates and sources
| Company | Service as listed | Rate | Source |
|---|---|---|---|
| Skyzone Aircon Pte Ltd | Aircon diagnosis fee (residential) | S$27.25 per visit | skyzone.com.sg |
| Snowflake Services LLP | Diagnostic visit (waived if you proceed) | S$30 per visit | snowflakeaircon.sg |
| City Cooling Pte Ltd | Checking | S$35 per unit | citycoolingengr.com.sg |
| A-Max Aircon | Troubleshooting | S$40 per job | amaxaircon.com |
| Blossom Engineering & Construction Pte. Ltd. | Troubleshooting | S$40 per job | blossomaircon.com |
| Coolest Aircon Service Pte Ltd | Aircon Repair | S$40 per visit | coolestaircon.com.sg |
| Doctor Cool | Aircon repair or troubleshooting | S$40 per job | doctorcoolsg.com |
| SmartCool Aircon Servicing Singapore | Troubleshooting | S$40 to S$80 per job | smartcool.sg |
| Thetop Aircon Service | Aircon troubleshooting repair | From S$40 per job | thetop.com.sg |
| Goodcool | Aircon Troubleshooting | S$43.60 per job | bestairconservicing.com |
| Aircon Boon | Ttroubleshooting [sic] | S$50 per job | airconsg88.com |
| Sky Blue Aircon Engineering Pte. Ltd. | Troubleshooting & diagnostics visit (from; waived upon repair) | From S$50 per visit | skyblueaircon.com |
| Jiaxing Holdings Pte. Ltd. | Onsite inspection checking fee (waived if the repair proceeds within 1 month) | S$54.50 per visit | jiaxing-aircon.sg |
| Heng Aircon Pte Ltd | Diagnostic check | S$60 per visit | hengaircon.com |
| Same Day Aircon Servicing Repair | Repair troubleshooting (fix quoted separately) | From S$60 to S$80 per job | urgentairconservicing.sg |
| Vois Pte. Ltd. | Aircon troubleshooting | From S$60 per unit | vois.com.sg |
| Airple | Aircon Troubleshooting | S$60.60 per job | airple.com.sg |
| Lion City Air Conditioner Services | Gas troubleshooting | S$87.20 per job | lioncityaircon.sg |
| Joydom Engineering Pte. Ltd. | On-site troubleshooting visit | S$100 per job | joydom.com.sg |
| Cool-Aire Aircon Servicing | VRF Troubleshooting - On site survey / Transport charges | S$150 per visit | coolaire.com.sg |
| Homeone Aircon | Compressor replacement labour, split (<3hp), parts excluded | S$600 per unit | homeone.com.sg |
21 companies publish an aircon repair, troubleshooting or inspection line. 11 of them price per job: their lowest matching rates run from S$40 to S$100 per job as printed, with S$43.60 per job in the middle. That middle figure is one company's real published rate, not an average.
The rest use other units, such as a S$27.25 diagnosis fee per visit or S$35 per unit for checking. Almost every line is a diagnosis or troubleshooting fee, not the cost of the fix, and none prices the repair of a tripping fault. Ask for the repair cost after diagnosis, and see the guide to aircon repair cost.
Wiring and isolator problems for an LEW
If the fault seems to be in the wiring, the isolator or a breaker, for example after a repeated aircon isolator trip, the job belongs to an LEW. EMA says electrical work in an HDB flat needs a Licensed Electrician, the class of LEW approved for loads of up to 45kVA. EMA's guide to engaging LEWs lists installation, repair or modification of wiring and repair or replacement of circuit breakers as LEW work. It says to verify the LEW's licence card before any work starts, and licensed workers can be searched on the ELISE portal. See how to check a licensed electrician.
HDB gives the estimated average lifespan of a PVC electrical cable as about 25 years, and an LEW can check whether old wiring needs replacing. HDB's electrical works guidelines do not allow new wiring to be embedded in concrete, walls or plaster, so it runs in surface trunking, above a false ceiling or behind carpentry.
NEXT STEP
See aircon companies in the directory with their published prices, the areas they say they cover and their sources.
Compare aircon companiesWhen to stop and call a professional
Otherwise, as a practical step, switch the aircon off and reset the breaker once, with dry hands. If it trips again, leave the aircon off. Never hold a switch on or tape it up.
Call an aircon technician for a fault in the unit and a Licensed Electrician for the circuit. You can compare companies that offer aircon repair in the directory. Tell whoever you call:
- Which breaker tripped: the RCCB or the aircon circuit's MCB.
- When it trips: at switch-on, after a few minutes or at random.
- Whether other appliances or aircon units were running.
- How old the unit is and when it was last serviced.
Questions
Why does my aircon trip only after a few minutes?
The delay on its own does not show the cause. Note how long the aircon runs before it trips, which breaker goes down and whether it happens every time. Pass these details to an aircon technician or a Licensed Electrician so they can test the unit and the circuit.
Is it safe to keep resetting the breaker?
No. Switch the aircon off and reset the breaker once. If it trips again, leave the aircon off and call a professional. A breaker trips to protect the wiring, appliances and people, and resetting it again does not fix the fault.
Can a dirty aircon cause the power to trip?
Do not assume dirt is the cause, because a trip needs proper diagnosis. Servicing still keeps the unit in good condition: the National Environment Agency (NEA) advises servicing aircon units regularly and having them inspected annually. You can compare aircon servicing prices in the directory.
Do I need a dedicated circuit for my aircon?
HDB's rules focus on the main switch rating: with a 30 amp main switch, a new 15A power point or 20A isolator for the aircon needs a permit, while 40 amp flats or flats upgraded under MUP or HIP need none. The CPSO notes that aircons generally use 15A Type M plugs. Ask an LEW what your flat allows.
Should I call an aircon technician or an electrician?
An aircon technician handles faults inside the unit. A Licensed Electrician handles the circuit, including the wiring, the isolator and the breakers. If you are not sure where the fault is, tell them which breaker tripped and when, and ask whether they handle it.
How much does it cost to diagnose an aircon that trips?
21 companies publish an aircon repair, troubleshooting or inspection line. 11 price per job, with lowest published rates from S$40 to S$100 per job as printed. Others charge per visit, such as a S$27.25 diagnosis fee, or per unit. Almost all are diagnosis or troubleshooting fees, and none prices the fix for a tripping fault.
Prices come only from the sourced company rates in the HomezyPro directory, shown with each company and its source.
Practical guidance for planning a home job in Singapore. Company prices come from the HomezyPro directory, each linked to its source; rules and safety points link to the agency or manufacturer that sets them. This is not a site inspection, a quote or professional advice for your home.
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