Protecting a microwave oven above a built-in oven

[triplstep]

Where in the code does it permit a cord and plug connected microwave oven to be protected by the same 240v 20-amp breaker protecting the oven?

The oven installation is a replacement; the microwave is not. The original installation from 20 years ago had a two pole 30-amp breaker protecting both, as well as a warming drawer below the oven.

I was adamant to have an individual 20-amp circuit for the microwave and ran a new one. But was I wrong in claiming it to be code? After all it is not a microwave hood.

The oven and microwave and warming drawer are stacked in a cabinet, with the warming drawer below the oven. The warming drawer was abandoned.

 

[retirede]

As long as both are fastened in place, and the load of each appliance doesn’t exceed 80% of the circuit rating, I think it’s permissible. 210.23(B)(2).

 

[Strathead]

As long as both are fastened in place, and the load of each appliance doesn’t exceed 80% of the circuit rating, I think it’s permissible. 210.23(B)(2).

I think there is more to unpack than this. BTW, what code cycle are you quoting? My 2020 code doesn't have that code section.

Where in the code does it permit a cord and plug connected microwave oven to be protected by the same 240v 20-amp breaker protecting the oven?

The oven installation is a replacement; the microwave is not. The original installation from 20 years ago had a two pole 30-amp breaker protecting both, as well as a warming drawer below the oven.

I was adamant to have an individual 20-amp circuit for the microwave and ran a new one. But was I wrong in claiming it to be code? After all it is not a microwave hood.

The oven and microwave and warming drawer are stacked in a cabinet, with the warming drawer below the oven. The warming drawer was abandoned.

So, you are providing a 120V plug in load and a 240v fastened in place load? Or does the oven also plug in?

 

[triplstep]

Thanks

The oven is fastened in place, the microwave is cord connected. There is no code cycle regarding this installation per se, say 2017. I'm an old guy, and I'm always after a safe installation. That said, if a double pole 240v 20 amp breaker with ties is compliant for both appliances then I won't charge for running a single pole 20 amp circuit for the microwave. It is good practice, imo, to separate the loads, but was it necessary? Looks like it wasn't.

The microwave is rated for 720 watts. The oven is rated for 3600 watts. Both less than 80%. I'm going to have to eat some pie.

 

[ramsy]

The microwave is rated for 720 watts. The oven is rated for 3600 watts. Both less than 80%.

Last 30yrs fixed range-hood microwave not allowed to exceed 50% of branch circuit rating 210.23(A)(2), if not a dedicated circuit.

New cord & plug range-hood microwave also requires dedicated circuit unless hardwired 422.16(B)(4)(3)

 

[retirede]

I think there is more to unpack than this. BTW, what code cycle are you quoting? My 2020 code doesn't have that code section.

So, you are providing a 120V plug in load and a 240v fastened in place load? Or does the oven also plug in?

I was referring to 2023.
It basically only limits the connected load of the circuit also serves lights or equipment not fastened in place.

 

[retirede]

Last 30yrs fixed range-hood microwave not allowed to exceed 50% of branch circuit rating 210.23(A)(2), if not a dedicated circuit.

New cord & plug range-hood microwave also requires dedicated circuit unless hardwired 422.16(B)(4)(5)

We’re not talking about a hood. It seems silly that we can exceed that for a MW that is not a hood.

 

[wwhitney]

As long as both are fastened in place, and the load of each appliance doesn’t exceed 80% of the circuit rating, I think it’s permissible. 210.23(B)(2).

I'm not seeing any requirement for each appliance to be less than 80% of the circuit rating if they are both fastened in place.

But the load being under 20A would be a bit tight if the microwave is 120V cord-and-plug connected and the oven is 240V. I guess you could have a 10A microwave (1200VA nameplate) and a 10A oven (2400VA nameplate).

The oven is fastened in place, the microwave is cord connected.

Specifying cord connected does not specify whether it is fastened in place or not. Is the microwave just sitting on a shelf, so you can unplug it and remove it? Or does it have a "built-in" trim kit that you'd have to dismantle in order to move it? I'd consider the latter to be fastened in place, depending on the details.

The microwave is rated for 720 watts. The oven is rated for 3600 watts. Both less than 80%. I'm going to have to eat some pie.

As the microwave is 120V, that's too much for a single 20A circuit. 720/120 = 6A, and 3600/240V = 15A, the sum is 21A.

Cheers, Wayne

 

[retirede]

I'm not seeing any requirement for each appliance to be less than 80% of the circuit rating if they are both fastened in place.
Cheers, Wayne

After re-reading it, you are correct.
The 80% only applies to “not fastened in place.” I’m not sure I understand the logic behind that.