Voltage fluctuations and loss of electrical feeds could be why a microwave isn’t working after a power outage. This post will shed some light on why this is happening and what you can do to prevent it happening in the future from an electrician’s perspective.
Microwave Wiring & Fault Finding
A microwave is connected to the home’s electrical system via a plug at the wall socket. The wall socket provides a standard voltage at a set frequency. This is typically 230 volts at 50 hertz (UK/AUS/NZ) and 120 volts at 60 Hertz (USA). The microwave is designed to work at that standard voltage.
If this voltage or frequency changes it will damage whatever appliance is plugged into the socket.
For example, when a fault occurs on the power network, the microwave can be exposed to a range of damaging conditions including high voltages, low voltages, lost feeds and wrong electrical frequencies.
All of these can cause the microwave to stop working.
A typical microwave contains a magnetron, electric motor and electronic components. All of these are designed to work at a designated voltage and frequency (230 volts, 50 Hz – Aus/NZ and 120 volts, 60 Hz USA)
If any of these components fail, the microwave will fail and many parts are too expensive or dangerous to replace.
For example, a magnetron in a microwave holds a lot of energy even when unplugged. This energy can result in the microwave giving someone a bad electric shock.
Let’s look at how a power outage would cause the microwave to not work.
Microwave Not Working After Power Outage? – Reason #1
Electrical Feed Still Offline (Lost Phase)
Likelihood: High – If your home is on three phase power, one phase might be still out.
If the property is on two or three phase power it means that two or three separate electrical feeds power the property.
The power outage could still be affecting one phase. This phase powers the outlet with the microwave.
It may seem that power is back on when actually one power feed (or phase) is still out.
This offline phase feeds the wall socket that the microwave is plugged into. Because there is no power to the wall socket the microwave won’t work.
This is only likely if your home has three phase power. You can check if you have three phase power by going to your electricity meter. A digital meter will have three LED indicator lights for three phase power and one LED indicator for single phase.
If your home is on single phase and the power is back, then it is more likely that the microwave has been damaged by high or low voltages.
Microwave Not Working After Power Outage? – Reason #2
Fluctuating High Voltage
Likelihood: High – common cause for damaged appliances after an outage.
As mentioned earlier, a microwave contains a magnetron, an electric motor, as well as electronic components such as the display.
All of which are designed to operate at a specific voltage. A high voltage, even if momentary, will cause these to potentially fail.
High voltages will cause electronic components like capacitors, inductors and semiconductors to short out and fail.
As you can see, high voltages can cause damage to almost every electrical component in the microwave. Low voltage can also damage a microwave, let’s look at how.
Microwave Not Working After Power Outage? – Reason #3
Low Voltage
Likelihood: High – possible if the microwave display is still working but the glass plate isn’t spinning.
Consistent low voltages can cause motors to draw more current and burn out (if used during a period of low voltage). The main motor in a microwave turns the glass plate. This can burn out under low voltage conditions.
How To Protect Appliances In A Power Outage
Install a Surge Protector
A surge protector will protect your appliances by taking fluctuating high voltages and sending them to earth via your homes earthing system.
This process ensures that your appliances are not exposed to damaging voltages. A surge protector is typically installed in the switchboard which will protect all appliances in the home.
You can also get multi boards with surge protectors installed. These multi boards will only protect whatever appliances are plugged into them.
Electricians Perspective
A fluctuating high voltage is the most likely reason a microwave wouldn’t work after an outage. The microwave magnetron, glass plate spinner and display electronics can all be damaged by high voltage. With this being said, replacing a magnetron is not a wise move as they can hold a lot of energy and be dangerous.
A damaged microwave should be replaced unless you are extremely competent at repairing due to the risks.
We Fix Faults is an electrician blog dedicated to discussing common electrical faults and finding solutions. If you have any questions or topics you’d like us to cover send us a message.