Kitchen remodel, electrical question

[John Gregory]

My wife and I are working on a plan to remodel our kitchen. The built-in oven is from 1976, smaller than the standard now so cannot be replaced in the current cupboard. My wife wants a built-in double oven. The current oven is on a 30 amp circuit. The new oven suggests a 40 amp circuit. The one oven draws 2500 watts (convection) the other one 2300/2100 depending on broil or bake. New wire could be run to the new oven with some difficulty. But I was wondering if the current 30 amp circuit could be used.
In searching for answers on the internet I found this comment:
"With that in mind, your stove could use up to 7200 watts without maxing out the 10-guage wire. (30 amps X 240 volts = 7200 watts) As to why they want a 40-amp breaker, probably just for a little extra margin."

Is that a valid comment?

Thanks,

[Fred Hargis]

We went through the same thing about 4 years ago, and in the end I might have been able to get away with using the old 30 amp circuit, but the risk wasn't worth it. Not just the risk of fire specifically, but also the risk the insurance carrier might have had an excuse not to pay a claim if something did happen. Just my opinion....

[Jamie Buxton]

It does seem like a 40 amp circuit would be overkill. The new oven draws only 2300 watts max? Or -- it is a double oven -- does each half draw 2300 watts? If the answer is that 2300 watts is the maximum draw for the pair, that's only 10 amps on a 230 volt source. 40 amps would be way overspecifying it.

Ovens, unlike the motors in our shops, don't have much of a turn-on surge. A 10-amp shaper motor might draw 40 amps for a few seconds at turn-on. But ovens don't have that inertia to get started, so there's no surge.

[Aaron Wingert]

Assuming the wire is properly sized for the load and assuming the breaker functions as it should, the worst thing that'll happen with the new oven is nuisance trips of the breaker. The overcurrent device is simply there to protect the wire, and if it trips then you know you need a 40 amp circuit and larger wire.

I'm a building codes inspector and can assure you that if your inspector is doing his job he's checking the required ampacity of the circuit for any given built-in appliance. It is easier to proactively make it right than it is to have to do it after construction has progressed and you get caught.

My suggestion would be to do it right, do it safe, and run the new wire and 40 amp breaker as the appliance's installation requirements dictate.

[Ben Franz]

I wouldn't consider trying to skirt the 40A circuit requirement. Even if it slips by the inspector (unlikely), there is a permanent risk of disaster. Then, when you sell the house, the buyer's property inspector will probably discover the problem and it will cost a lot more to fix it then than it will cost to do it right now. Fred brought up insurance issues and who needs that in their life.

[Jason Hallowell]

Check the wire size for the circuit. If the wires are big enough to handle a 40A circuit, you just need to replace the 30A breaker with a 40A. If you are re-using the old outlet, just make sure that it's rated for at least 40A.

[Jamie Buxton]

Here's my guess: the oven manufacturer doesn't tailor its house-wiring recommendations on a model-by-model basis. Instead, they give a blanket recommendation based on the biggest unit they build, plus some safety factor. That's the only way I could see to justify recommending a 40-amp circuit for a 10-amp oven.

[John Morrison60]

John

You also may encounter the need for a four conductor wire (code now) rather than the 2 conductor wire that was probably installed for your old circuit. Most new appliances specify a four wire connection even though they do not use the neutral
conductor.

I would say, have an electrician install the correct new wire.

Good luck.

John