Why is There No Power to Part of My House?
Electrical Safety Guide · Verified against Australian Standard AS/NZS 3000
A partial power outage occurs when a single sub-circuit breaker or safety switch has tripped, a single phase has dropped out in a three-phase property, or an open-circuit neutral has failed. The rest of your home remains powered because domestic switchboards divide electrical loads across separate sub-circuits.
Immediate Safety Warning
If some lights glow dimly while others shine unusually bright, or if appliances run sluggishly, turn off your MAIN SWITCH immediately. This is a telltale sign of a 'floating neutral', which can send 415 volts through 240V appliances and destroy electronics or cause electrocution.
Understanding Partial Outages
When only part of your home loses electricity, your electrical installation is actively isolating a fault to protect the rest of the property.
Common Scenarios:
- Only Lighting Out: Lighting circuit RCBO has tripped, commonly caused by a blown globe creating an internal short or water in an exterior spotlight.
- Only Power Points Out: Power sub-circuit has tripped due to an overloaded heater or faulty appliance.
- Multiple Rooms on One Side Out: Typical of three-phase properties where Phase 1 or Phase 2 has disconnected.
Our master electricians respond promptly across Melbourne West (Mon–Sat 7am–6pm) with diagnostic multimeters and insulation testers to find and fix partial outages rapidly.
Common Causes of This Issue
1. Single Tripped Circuit Breaker / RCBO
The breaker dedicated to that specific section of the house has tripped due to an overload, faulty appliance, or water ingress.
2. Blown Sub-Board or Master Phase Fuse
In homes with three-phase power, a service fuse on the street pole or main board can blow on one phase, leaving one-third of the house without power.
3. Open Circuit / Loose Terminal in Junction Box
A deteriorated cable termination in the ceiling or wall has broken, cutting power to all downstream rooms on that circuit.
4. Distributor Grid Outage on Single Phase
Electricity distributors (Jemena, Powercor) occasionally lose one phase on the local street network during maintenance or storm events.
What You Can Check Safely vs What Requires a Licensed Electrician
✅ What You Can Check Yourself
- Check the main switchboard and verify if any toggle switches are in the OFF or middle position.
- Check with your neighbours to see if they are experiencing similar partial power issues.
- Unplug all appliances in the unpowered rooms before attempting to reset any tripped breakers.
⛔ Requires a Licensed Electrician (REC)
- Testing voltage across all phases (Line to Neutral: 230-240V; Line to Line: 400-415V).
- Locating and repairing open neutral or active faults in roof cavities.
- Replacing blown service fuses or defective sub-board isolators.
- Coordinating emergency repairs with network distributors (Powercor/Jemena) if supply mains are faulted.
Under Victorian law, all fixed electrical wiring, switchboard modifications, and power point replacements must be performed by a Registered Electrical Contractor (REC) and issued a Certificate of Electrical Safety (CES).
Frequently Asked Diagnostics Questions
Why do some power points work in the room while the lights don't?
Australian standards mandate that lighting and power points must be wired on separate sub-circuits. A tripped lighting breaker will not affect power points in the same room.
What should I do if half my three-phase house has no power?
First check your main switchboard. If all breakers are ON, contact your electricity distributor (Powercor or Jemena in Melbourne West) to check if an incoming network phase is down.
Need On-Site Diagnostic Assistance?
Nick is available for emergency fault finding across Melbourne's West