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Question about microwaves and dedicated circuits. What's the difference in circuit requirements (amps? dedication? something else?) between microwaves in these locations:

  1. mounted under a cabinet over the range
  2. sitting on a countertop
  3. mounted under a cabinet (but not OTR)
  4. mounted under the countertop (drawer-style)
  5. sitting on a shelf somewhere above the counter
  6. sitting on a shelf somewhere below the counter?
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  • @SteveSether The amps may be higher yet, since the power factor for the magnetron may be considerably less than 1. Oct 5, 2020 at 5:40
  • @SteveSether OK, so it's like an "850 watt/1200 watt" PC power supply where that's the DC-side output, and it actually nameplates for 10A / 13A respectively (1200/1560W). Oct 7, 2020 at 3:54

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The code doesn't address microwaves as a specific appliance, but NEC 210.23(A)(2) Utilization Equipment Fastened in Place limits equipment to 50% of a circuit when shared with lighting or other equipment not fastened in place.

So if it's fastened in place, which would likely place it on a designated kitchen circuit, a shared kitchen circuit would have to be 20A, so a microwave would not be able to exceed 1200W without requiring a dedicated circuit.

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    The "fastened in place" seems weird. You could have a microwave on a shelf (not fastened in place) vs. a drawer microwave (fastened in place), but they'd have different requirements.
    – Huesmann
    Oct 4, 2020 at 21:37
  • Also, you could place your OTR microwave on the counter and it would have different requirements than if you mount it over the range.
    – Huesmann
    Oct 4, 2020 at 21:42
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    If it isn't fastened in place it is more likely you will replace or move the appliance if it causes tripping, but the code doesn't completely protect you from doing stupid stuff. If it did it would outlaw multiple 15A receptacles on 15A breakers since you can plug in two 1500w heaters. Oct 4, 2020 at 23:01
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    An appliance that is fastened in place is guaranteed to be (very specifically) there. An appliance that is not fastened in place may or may not be there at all. And as already noted, it can be moved to another outlet if it's a problem. In the modern kitchen it's a very good idea to exceed code minimum requirements for the sake of not having nuisance trips. Few OTR microwaves are convertable to sit on the counter, as they often have a vent van built into the bottom of them, as well as being relatively wide compared to normal microwaves.
    – Ecnerwal
    Oct 5, 2020 at 1:11
  • But if you put it on the counter there’s no reason to USE the fan.
    – Huesmann
    Oct 5, 2020 at 1:44

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