My tenant just moved out and I'm prepping for at new one. The father-in-law of the exiting tenant was an electrician and added a new circuit for a microwave above the stove and they swapped out the Electric stove for a gas stove.
He put in a new 20 Amp breaker and feed the Microwave with 12 gauge wire but came back down with 14 gauge to feed the stove.
Yes replace the 14 ga wire and I would back charge the tenant for the work to fix their error. 14 ga wire should not be present on a 20 amp breaker circuit.
Does the current requirement for both the microwave and gas stove add up to less than 15 amps. If so, you could swap the 20A breaker for a 15A breaker.
But maybe read the code on kitchen appliance circuits. I have a vague recollection that a microwave oven needs it's own circuit. If that's true, it may be a bigger job to run a new line to the gas stove.
If the two outlets are on the same 20 amp breaker, I would replace the 14 with 12. Something about a 15 A circuit for the stove electronics rings a bell, but if its not a dedicated circuit the whole thing really should be 12 gauge wire.
A breaker protects not only against an electrical device drawing too much amperage, but also the wiring drawing too much amperage. My understanding is that 14 gauge wire should be protected by a breaker rated no stronger than 15 amp, regardless of whether the entire circuit or only a portion is 14 gauge.
Someone looking at the wiring around the circuit breaker panel only sees the gauge attached to the breaker, and may never find a smaller gauge wire further along the circuit.
I thought the recommendation today is for a dedicated 20 amp circuit for a microwave.
I'd suggest you ask for amperage and wiring recommendations from a local business that sells microwaves and electric stoves. Check also the owner's manuals for your microwave and stove (many today can be found online). Not all electricians strictly follow the electrical code, so you should have some basic understanding.
I am the specious type and when someone say they removed the electric stove and added outlets.
That sends shiver down my spine. It would be all too easy splice into the old range circuit and get the outlets but very dangerous.
Let’s play what if the worst thing happens game.
Scenario 1
You rent the house to a young woman. Sometime later the house burns to the ground the new mother escapes but not the new baby. Now you have to look her in eye and explain how you allowed a relative of a former tenet to perform unsafe, unlicensed unpermitted, uninspected electrical work that led to her child’s death.
Scenario 2
You pay an electrician 2 months’ rent. Yes it is painful to your cash flow but no one dies and you can sleep at night.
I just looked up one brand of over the range Microwave. That Particular one required either a 15 or 20 amp circuit.
A gas range requires very little current. The heating of both the oven and burners is done with gas. And that would be the heavy draw in an electric range. The timers and sensors in the gas range would only draw an amp or two. OTOH, an over the range microwave is supposed to have a dedicated circuit.
Back in the day electric ranges had three wire circuits. Two hots and a ground, n o neutral. When ranges with electronics, timers, and controls came along they "cheated" and allowed them to use the ground as a neutral. New Installations have a four wire circuit, two hots, a ground and a Neutral. There is still not requirement to retrofit a four wire circuit. I have just purchased a new range for one of my rentals and they asked me if I wanted a three or four wire cord. I went with a three wire because that is how the house is wired.
So you are on the right track to replace the breaker. It would be better to separate the two functions. Two separate dedicated circuits with their own breaker. If you are limited for space int he panel you can use a split or mini breaker.
You should replace the #14 regardless. All the wire on that one circuit should be the same gauge period. Then you can put a 15amp or 20amp breaker on it.
However, rules have changed in some places, the stove requires a dedicated line here and the breaker has to be sized per the appliance being on that circuit.
In the old days this was not true and the breaker was sized per the wire gauge.
You'll get an argument depending on which electrician you ask about this fact.
I'm from the old school where wire size determined breaker size but I have to change with the times. I guess.