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Phil , Mechanical Engineer
Category: Electrical
Satisfied Customers: 7490
Experience:  Retired electrical contractor, 51 years experience.
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How can I tell if my circuit breaker box needs to be replaced?

Customer Question

How can I tell if my circuit breaker box needs to be replaced? My kitchen was remodeled recently, and the breaker for the new oven trips if I have 3 or more elements going at once. Also, the microwave breaker keeps tripping. The contractor says it's the breaker box. However, an electrician told me the box is fine. Any guidance?
Submitted: 4 years ago.
Category: Electrical
Expert:  Phil replied 4 years ago.
All work must be permitted and inspected. WE KEEP GOING UNTIL YOU HAVE THE INFORMATION YOU NEED. I must come and go. This is step One.

Hello, welcome to Just Answer.

The wiring to the stove and to the microwave need to be their own separate circuits and the wire and breaker need to be sized for the load. That will be the first thing to check.

There are two ways to check that. You can look on the name plate of each of those appliances for the full load amperage rating (FLA) and then check the breaker size on that circuit.

Or you can use a clamp on type amp meter, clamped over one leg of the power to the appliance and read its amperage draw directly.

Here are an example of what will work:

- Amperage rating on the microwave is 13-15 amps, breaker on that circuit is 20 amps. and wire is size 12 awg copper. You are allowed 16 amps constant load on a 20 amp breaker. 15 amps is well within that range. you could safely put 20 amps on that breaker for a short period of time... but only 16 amps constant load.

Here is an example that will not work:

- Same microwave, drawing the same 13-15 amps, but breaker size is 15 amps and wire size is #14 AWG. That will overheat the breaker and cause it to trip. Especially if the breaker box is in a hot location or in the direct sun light.

Its a good guess that the house wire sizes may be a bit small, and that the breakers to protect that wire and prevent a fire are likewise small.. and not sufficient to carry the electrical current your appliances are using.


Tell me the breaker sizes on those two circuits and what the appliance name plates say about the full load amperage.

The age of the box will generally have nothing to do with these breaker and wire size issues. If the wire size is inadequate you will gain nothing by changing the box. Checking the wire size will be the next step.

We can go from there. Phil
Phil, Mechanical Engineer
Category: Electrical
Satisfied Customers: 7490
Experience: Retired electrical contractor, 51 years experience.
Phil and 2 other Electrical Specialists are ready to help you
Expert:  Phil replied 4 years ago.
Hello again, thanks for accepting... I need to clarify a bit however.

If the microwave is free standing it can be plugged into a circuit with other outlets on it as long as it does not exceed 50% of the circuits total amperage rating.

The total load on the circuit and its circuit breaker however applies as noted in my first response. We can continue this discussion as you need to, on the same dime so to speak.


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