A microwave doesn’t require its own dedicated circuit for any specific reason but the circuit must be able to handle the total load of the appliance. This means that the microwave and any other wall outlets and appliances on the circuit must not exceed the current carrying capacity of the cable.
The circuit must also have a circuit breaker or fuse that protects the cable if it was to be overloaded.
This post will go into four considerations you should make when deciding if a microwave needs a dedicated circuit.
Microwave Wiring From Outlet To Switchboard
A standard household microwave is plugged into a wall socket. This wall socket is wired with a cable designed to handle the load of whatever is plugged into it.
This cable finishes in the switchboard where it is protected from overloading and short circuits via a circuit breaker.
If the cable wasn’t able to handle the load of the microwave it would heat up before eventually melting the insulation and catching fire.
Overloads are a major cause of house fires.
Without circuit breakers it would be hard to determine if cables are heating up because they are hidden behind walls and ceilings. This is why the correct fusing is essential.
Let’s look at four considerations to ensure that the microwave circuit is properly wired and protected with a circuit breaker.
1. Check Microwave Specs Online
The paper installation manual which comes with the microwave will have its electrical specifications.
If you have lost the manual it should be also available online via the manufacturer or suppliers website.
The electrical specifications for the microwave will state the:
- Power rating in watts.
- Required voltage (microwave will fail when the voltage isn’t correct such as during surges).
- Frequency
- Operating current
- Fuse rating (a guideline)
We are interested in the operating current and fuse rating. If the operating current of the microwave is less than the current carrying capacity of the circuit then we are happy.
Size Of Cable In Microwave Power Outlet
The power outlet for the microwave will be wired with a cable that is good enough or too small for the microwave.
This will require opening the power outlet to check the size of the cable it is wired into. Doing so may require shutting off power to the circuit to be safe.
If you don’t want to check behind the wall socket I will give you a general guideline as an electrician.
In AUS/NZ a power socket will typically be wired with 1.5mm2 or 2.5mm2 cable.
1.5mm2 cable has a circuit breaker which will trip above 16A of current and a 2.5mm2 cable will have a breaker tripping at 20A.
Microwaves will draw far, far below what these breakers will trip at. This means that if your power outlet contains either 1.5mm2 or 2.5mm2 cables it will be fine unless…
Check Other Wall Outlets And Appliances On Same Circuit
Often circuits in a kitchen are wired together. This means that other power outlets in a kitchen are connected.
In this case you need to take into account the total current of all appliances that will be on the same circuit at the same time.
You can have appliances that collectively draw more than 16A or 20A but because they are unlikely to be used at the same time it won’t overload the circuit.
Common appliances could include fridges, blenders, kettles and dishwashers. Ovens and stovetops should be on their own dedicated circuits.
Check the specs for these appliances which can be found online.
Cable Protection Via Circuit Breakers
If the cable is sized at 2.5mm2 it should have a circuit breaker (in the switchboard) protecting it if 20A or more is consumed for a period of time.
This protects the cable.
If the breaker was rated at 32A (too big) then the cable would catch on fire before the breaker trips causing an obvious safety hazard. For this reason the cable should be fused at or below its current carrying capacity.
Electricians Perspective
A microwave doesn’t need a dedicated circuit unless it draws more current than the cable allows. If a breaker keeps tripping with the microwave plugged in then it could signal that the circuit is overloaded. In this case you should work out the total loading of appliances on the circuit and consider adding new circuits to share the load across multiple cables.
We Fix Faults is a blog dedicated to electrical troubleshooting. If you have any questions send us a message above.