Power Trip During a Thunderstorm: Normal or a Fault?

Timing tells you: a lightning trip resets first time; a water trip follows the rain and keeps coming back.

For trips on humid nights without rain, see why power trips at night.

Where does rain get into an HDB flat's wiring?

In most HDB flats, water reaches the wiring at a few exposed points:

• Yard and balcony sockets, including the washing machine point.
• Sockets and switches by rain-facing windows.
• The aircon condenser isolator on the ledge.
• Lights, doorbells and gate points hit by corridor washing.
• Ceiling lights under a leak from upstairs or the roof.

HDB notes that "untreated ceiling leaks may also damage electrical items" (HDB: Ceiling leaks). If water reaches a light, switch its MCB off and leave it off. On the top floor, report the roof leak to your town council first.

No. Wait until the lightning has passed, unplug your electronics, then reset the RCCB once.

1. Wait until the thunder stops: MSS notes lightning can strike from a cloud more than 10 km away.
2. Unplug your electronics.
3. Push the RCCB lever back up once.
4. If it trips again, switch every single-pole MCB off.
5. Reset the RCCB, then switch the MCBs on one at a time.
6. Leave off the MCB that trips it and have that circuit checked; the full routine is in why power keeps tripping.

If a socket got wet, switch its MCB off and leave it off; don't dry it with a hairdryer or spray it. If nothing has tripped but the corridor is dark, see who to call for an HDB power trip.

Unplug electrical appliances and electronics such as computers and TVs, as the Singapore Civil Defence Force (SCDF) advises, because lightning surges can damage them.

The SCDF emergency handbook says to "unplug electrical appliances and other electronic items e.g. computers; power surges caused by lightning can damage these items", and to avoid a shower or bath during a thunderstorm (SCDF: Emergency handbook). Start with the TV, computer, router and chargers, and switch aircon and water heaters off at their isolators. An appliance that now trips the RCCB may be surge-damaged: keep it unplugged.

Do surge protector power strips help?

Partly. A surge strip absorbs small spikes for what's plugged into it, but won't stop RCCB trips, wears out after large surges and can't stop a direct strike. Plain extension strips give no surge protection.

Power strips sold in Singapore must carry the SAFETY Mark (Consumer Product Safety Office: Controlled goods booklet). Surge protection at the DB box is licensed electrical worker work.

Test the RCCB, inspect outdoor points and label your MCBs, ideally in October:

• Press the RCCB's "T" button; the power should cut off. HDB advises a monthly test, with computers off first.
• Look at yard, balcony and ledge sockets and isolators for rust, cracks or missing covers.
• Check ceiling lights under any damp patch.
• Label your MCBs so you know which circuit drops.
• Save SP Group's 24-hour supply line, 1800 778 8888, and your town council's 24-hour Essential Maintenance Service Unit (EMSU) line; each town council has its own number.

If the power doesn't cut off, HDB says the RCCB may be defective: have a licensed electrical worker replace it. Switch off the MCB of any rusty or cracked point until it's repaired.

SG QuickFix diagnoses power trips from $80. Repairs and parts are priced separately.

The price rises with several wet points, concealed or ceiling wiring, or replaced parts; roof leak repair is the town council's job. For an accurate price, send a DB box photo and say whether it tripped in lightning or rain. See also the full electrician price list for Singapore.