A power trip is a measurement, not a guess at the switch

When an HDB or condo RCCB trips in Singapore, the usual cause is earth leakage in milliamps, not a failed appliance you can see. A like-for-like 30mA RCCB replacement is from S$138 to S$480. A DB upgrade with Type A RCBOs is S$480 to S$1,800. Resetting a breaker that trips again the same night is how a humid monsoon becomes a burnt neutral.

An RCCB, sometimes called an ELCB or an RCD, compares current going out on the live with current coming back on the neutral. The difference is leakage to earth. EMA practice in Singapore homes is a 30mA device on the circuits that need personal protection. A trip at 30mA is the device doing its job. A higher threshold, or a breaker that has been bridged, is not a repair. An MCB trips on overload or short circuit, which is a different symptom: it trips when a kettle and an oven share a tired 20A circuit, or when a cable has shorted. If the RCCB trips with every MCB off, the fault is often in the board, the neutral, or a shared leakage path. If it holds until one MCB is turned on, that circuit is the search.

The half-split test is how that search stays short. With the main RCCB reset and all MCBs off, turn MCBs on in halves until the trip returns, then halve that half. Unplug appliances on the guilty circuit and try again. A trip with nothing plugged in is cable, a wet joint, or a fixed appliance such as a storage heater or an oven. Monsoon weeks raise leakage because humid air and wet aircon isolators lower insulation resistance. Several healthy appliances can add up to more than 30mA even when none of them is dead. That is why a new fridge is blamed and the real total is the fridge plus the heater plus a damp balcony light.

Type AC, Type A and Type B are not marketing grades. Type AC sees ordinary alternating leakage. Type A also sees pulsating DC, which is what many inverter aircons, washing machines and induction hobs produce. Type B also sees smooth DC and is the conversation for some EV chargers, which is a different guide. Hager, ABB and Schneider all sell 30mA devices in these types. Putting a Type AC RCCB back in front of a house full of inverter loads is how the device trips on a waveform it was not built to measure, or fails to see a fault it should. The electrical DB load calculator is the check when the trip is actually an overloaded MCB and the flat needs another circuit.

Homey Furnishing Pte. Ltd. (ACRA UEN 202018148K), 27 Mandai Estate, #06-10 Innovation Place, Singapore 729931, carries the permit-exempt portion of this work. V On Construction Pte. Ltd. (ACRA UEN 201611708H), listed on the HDB Directory of Renovation Contractors, carries any scope that needs an HDB renovation permit. Those two invoices are not interchangeable. Final-circuit residual current protection at 30mA is the EMA expectation for household safety. Opening a DB and changing protective devices is licensed electrical work. Homey Furnishing coordinates the visit. The electrician signs the test. Bridging a breaker is not a grey area.

Spend ten minutes with a torch, your phone camera, and a tape before you buy a product or book a hack. Write down what you see. The safe checks below do not ask you to open a live wire, cut a pressurised pipe, or lean out of a window. Write down the time, the weather, which breaker moved, and what had just been switched on. Press the test button only once, with lights you can live without. Do not measure inside the board with a multimeter unless you are the licensed person.

Stop at the red-flag column. Stop if the device will not reset, if anything smells hot, if the cover is missing, or if you are about to bridge a breaker to get through the night. The reason DIY fails is almost never a lack of effort. It is that the tool or chemical makes the next professional repair harder, or it hides a leak, a live conductor, or a deposit line until the damage is larger than From S$138 to S$480 for a like-for-like 30mA RCCB, and up to S$1,800 when the board is rebuilt.

This is the sequence a careful technician uses so you can tell a shortcut from a finished job. Tools stay in the van. Readings and photos go on the same worksheet as the price. The electrician uses an RCD tester for trip time and milliamp, an insulation-resistance tester on the guilty circuit, and a clamp meter. The cover goes back with a label. Tools do not stay in the DB.

1. Step 1. Make the area safe and confirm the symptom still matches the photos. For A power trip is a measurement, not a guess at the switch, that means Stop if the device will not reset, if anything smells hot, if the cover is missing, or if you are about to bridge a breaker to get through the night.
2. Step 2. Measure before touching the finished surface. Write down the time, the weather, which breaker moved, and what had just been switched on. Press the test button only once, with lights you can live without. Do not measure inside the board with a multimeter unless you are the licensed person.
3. Step 3. Set protection and lay out the tools that belong to this material. The electrician uses an RCD tester for trip time and milliamp, an insulation-resistance tester on the guilty circuit, and a clamp meter. The cover goes back with a label. Tools do not stay in the DB.
4. Step 4. Carry out the repair in the order the material allows. a breaker is bridged, a Type AC device is fitted in front of inverter loads, or the trip threshold is raised above 30mA is the failure this order is written to avoid.
5. Step 5. Test in place. The test button drops the RCCB. The tester record shows a trip within the 30mA band. The circuit that leaked is named. The board schedule matches the flat.
6. Step 6. Clean, label the photographs against the invoice lines, and leave the statutory openings, weep holes, access panels and labels visible.

The order matters because a breaker is bridged, a Type AC device is fitted in front of inverter loads, or the trip threshold is raised above 30mA is what happens when a step is rushed. Handover is a measurement, not a handshake. The test button drops the RCCB. The tester record shows a trip within the 30mA band. The circuit that leaked is named. The board schedule matches the flat. If the reading or the water test fails, the visit is not closed and a second line is priced before anyone leaves. Permit work, if the diagnosis has moved into hacking, waterproofing, or a new layout, stops here and is repriced through V On Construction Pte. Ltd. UEN 201611708H.

Diagnosis is not free because the instruments and the licence are the job. A device swap is the small band. A board change is the band when the old RCCB cannot see the loads you now own. Prices below are 2026 Singapore bands for the described scope. They are not a coupon and they are not a guess after an unopened door. A second trade, such as a PUB licensed plumber or an EMA licensed electrician, is named when the law requires it rather than buried inside the labour line. Compare rows by what they include. The planning-life column belongs to that row only.

2026 SGD scope bands

Brand, material and lifespan

Open the electrical DB upgrade page and the load calculator before you buy a larger main switch. A larger main switch does not cure leakage.

Three worked jobs show how the same symptom is priced differently in a new BTO, an older resale flat, and a private condo or landed house. The totals are the lines a household actually paid, not a national average. Permit-exempt invoices are issued by Homey Furnishing Pte. Ltd. UEN 202018148K.

Case 1: 4-room BTO in Punggol

The RCCB tripped on wet evenings. Half-split found the balcony light. A Type A RCBO on that circuit and a dried joint were S$420. The rest of the flat stayed on. Two hours.

Case 2: 28-year resale flat in Tampines

The test button did nothing. The board was a single Type AC RCCB feeding inverter aircons and an induction hob. A labelled DB change with Type A devices was S$1,450. The old board was not bridged for the week in between. The family used a temporary supply plan the electrician set.

Case 3: 2-bed condo in River Valley

A tenant reset the breaker six times. The storage heater element was leaking. Heater isolated, RCCB tested and left in place because it still tripped at 30mA. Diagnosis and isolation S$240. The heater replacement was a separate licensed line.

Book the board on the DB upgrade page and run the load calculator if the trip happens when two appliances start together. Send the photos and the measurements from the ten-minute check. The reply prices the band on this page against what the photos actually show.

• Book the DB diagnosis
• DB load and circuit estimator
• Lighting faults that trip with the lights