A heater trips the ELCB when current leaks to earth — usually a heating element that has absorbed water, a tank drip reaching wiring, or moisture inside an instant unit. In Singapore that device is a 30mA earth-leakage trip, so treat it as a safety signal. Switch off at the isolator and stop resetting it. AOT diagnoses from S$80.
What the ELCB is actually telling you
The ELCB (nowadays an RCCB or RCBO in most Singapore flats) is a residual-current device. It compares the current going out on the live wire with the current coming back on the neutral. If a few milliamps are escaping to earth instead of returning, it trips. That is different from a tripped MCB, which is overload or a short circuit. A heater that trips the earth-leakage device is wet somewhere, or its insulation has broken down — it is not "drawing too much power".
That distinction matters because resetting the breaker does not fix anything. Water plus electricity inside a heater gets worse each time the element is energised.
Symptom to cause: what to look at first
| What you notice | Most likely cause | What a technician checks |
|---|---|---|
| Trips the moment it is switched on | Water inside the element, or insulation gone | Insulation resistance test on the element and its cable before anything is replaced |
| Runs 10–20 minutes, then trips | Element breaking down as it heats, or a slow tank / tile drip | Element test hot and cold, plus staining under the tank and at the relief pipe |
| Trips only while the shower runs | Moisture in an instant unit casing, or a splash leak onto terminals | Casing opened, water tracks on the terminal block and control board |
| Trips and part of the flat goes dark | Fault on a shared circuit; the heater may not be the culprit | Other loads isolated one at a time, each circuit tested for earth leakage |
| Trips more in wet weather | Condensation, or a pipe / roof leak reaching the cable run | Cable route inspected, insulation test repeated under load |
| Started right after a new install | Element knocked in transit, wiring swapped at the isolator, earth not bonded | Polarity, earthing and terminations re-checked at the isolator and the unit |
| Trips but the water still heats | Ageing RCCB, or another appliance leaking on the same circuit | Breaker tested on its own, other appliances isolated and tested |
What to do before anyone arrives
- Switch the heater off at its isolator — the switch beside the unit, not just the wall switch outside the bathroom.
- Leave the breaker off. Do not reset it again "to see if it holds".
- Do not open the casing or the ceiling panel yourself; a storage tank holds hot water under pressure.
- Put a towel or container under any drip, and photograph the unit, the isolator and the ceiling panel. Photos usually shorten the visit.
- If water is running through a ceiling or light fitting, switch off that lighting circuit too and call us.
Repair or replace?
Repair makes sense when the fault is the element, thermostat, thermal cut-out, isolator or the cable to the unit — the tank and body are still sound. Replacement is the honest answer when the tank is leaking, the casing is corroded, or a repair would cost a large share of a new unit on an already old heater. A typical HDB storage tank is around 15–25 litres; if yours has already been patched once, patching it twice rarely pays.
What happens when you engage AOT
You send photos on WhatsApp, we give a from-price and the earliest slot, then a technician tests the circuit and the unit on site before touching anything. The scope and price are confirmed in writing before work starts. Diagnosis is from S$80 labour; replacement labour is from S$180 for an instant unit and from S$280 for storage. The heater unit, parts and GST are extra. Hours are Monday to Saturday 08:00–17:00, closed Sunday and public holidays — not a 24-hour service.
Frequently asked
Is it safe to keep resetting the ELCB?
No. The trip means current is going to earth somewhere. Resetting it repeatedly keeps energising a wet element or damaged cable, and the fault spreads. Switch the heater off at the isolator and leave the breaker off until it is tested.
Should I repair or replace a heater that trips the ELCB?
Repair if the fault is the element, thermostat or wiring on a sound unit. Replace if the tank or casing is leaking or corroded — a seeping tank cannot be resealed reliably.
How much does it cost to check a heater that keeps tripping?
Diagnosis from S$80 labour. Parts, the heater unit if replaced, and GST are extra. Price is confirmed before work starts.
Why does it trip only sometimes?
Intermittent means moisture rather than a dead short: an element that leaks to earth once hot, condensation in an instant unit, or a drip that only reaches wiring in heavy rain. It has to be tested under load.
Do I need a plumber or an electrician?
Both scopes can be involved. The water side of a heater is licensed plumbing work; the electrical side must be done or supervised by an EMA-licensed electrician. AOT covers both, so you are not caught between two trades.
Do you attend on Sunday?
No. Monday to Saturday 08:00–17:00, closed Sunday and public holidays. Same-day Monday to Saturday when the crew is slotted; after-hours WhatsApp is dispatch, not a fixed response time.
Related: Repair or replace a water heater · Common heater problems · Storage vs instant water heater · What photos to send for a quote
ALPHA & OMEGA TRINITY PTE. LTD. (UEN 201215586K) · 32 Old Toh Tuck Road, I. Biz Centre #03-11, Singapore 597658 · WhatsApp +65 8151 8857 · Office +65 6816 2462 · [email protected] · PUB plumber Lam Kien Choon WS16882018 · BCA L1 ME01 / ME06 / ME12 to 1 Sep 2028 · bizSAFE Level 3 (E18947) to 27 Jul 2029 · Mon–Sat 08:00–17:00, closed Sun & PH.