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Rainy-day breaker trips traced to water ingress in switch box

Aircon case in Pasir Ris, Singapore: electrical/control traced to rusty outdoor switch box with water entry after targeted diagnosis checks.

Case details

What client reported

The breaker often tripped during rainy evenings. On dry days, the system could run for long periods without fault.

ProblemElectrical / control
UnitMitsubishi Electric · Wall-mounted · 14 years old
LocationLanded · Pasir Ris, Singapore

What we found

Rain-linked trips often point to water entry in the power path. We checked each point in order.

  • Compressor winding checks were normal
  • Trips matched wet weather periods
  • Outdoor switch box had rust and worn seals
  • Trip happened again when moisture reached the switch area

Water entered the outdoor switch box and created a leak-to-ground path. The breaker tripped to protect the circuit. The compressor was not the cause.

What we did

We replaced the damaged switch box and improved weather seals at cable entry points. No compressor replacement was needed.

Trips stopped after switch-box correction. System operation stayed stable through rainy periods.

Timeline

Day 1

Repeated breaker trips during wet weather

Day 1

We checked the switch box under wet conditions and saw the same trip pattern again

Day 1

Isolator fault confirmed and corrected

What we learned

Why rain-linked trips are often an external electrical-path issue.

  • If trips cluster around wet weather, check outdoor switches and entry seals before blaming the compressor.
  • A compressor fault usually appears across all weather, not mainly during rain.
  • Testing the power path under wet-condition simulation can isolate the true source quickly.

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