Clock & fan works but microwave doesn’t!

Hi @jeaninehunt

I commented that I was surprised that the fuse in the microwave hasn't blown and that the circuit breaker trips instead.

Microwave oven fuses have a lower current rating than circuit breakers so to me this indicates that the problem is not in the oven.

The only caveat to this is if the circuit breaker is a GFCI type breaker or the oven is connected to a GFCI wall outlet, then the problem could be in the oven. Both are safety devices designed to prevent electrocution of the user in the event of an electrical fault occurring in an appliance etc making it "live"

If for example somewhere in the HV (high voltage) section of the oven i.e. HV transformer, HV Capacitor, HV diode and magnetron either the components or their associated wiring are in contact with an earth, for whatever reason, this will cause the GCFI to trip once the oven is started. The HV section is only connected to the power once the oven is started

I suggested that you try turning off the vent fan before starting the oven, just in case the circuit breaker was already near its maximum load rating, i.e. it has the maximum number of devices connected to it so it's supplying as much current as it is designed to pass and that turning on the oven plus the vent fan was the last straw and it tripped.

If the oven still trips with the vent fan off and the oven turned on, how may other appliances/devices are affected when the breaker trips? It may be that there's too many circuits for the breaker to handle or there's a problem with the breaker itself.

Another test you could do if the oven is plugged into a wall outlet that is easily accessible, is to unplug the oven and then plug in a filled electric kettle and turn it on and check if the breaker trips. Most kettles require the same amount of power as an oven so if the breaker does trip, this points to problems in the breaker circuit and you may need an electrician to sort it out.

This is all conjecture at this stage but it is based on the fact that if there's a problem in the oven then the fuse should blow and nothing in the oven would work and not the breaker (except if it's a GCFI). That's what the fuse is for.

Slept well,

Cheers