04:01PM | 11/23/02
Member Since: 11/18/02
30 lifetime posts
Does the NEC specify what is required to operate a microwave oven - the kind that is mounted permanently in a cabinet, and the smaller kind found on countertops?
NEC 110.3.B says “equipment shall be installed and used in accordance with any instructions included in the listing or labeling.”
I recently purchased a small countertop unit. Rated Power Consumption 1000 watts.
The manual says “For safety purposes this oven must be plugged into a 15 amp circuit. No other electrical appliances or lighting circuits should be on this line.” Then it says “Your microwave oven can easily be placed in your kitchen, family room or any other room in your home.” I contacted them to ask about the discrepancy (How can you easily move an appliance to any room if it requires a dedicated circuit?), but their final comment was simply “I'm sorry you are unhappy with our recomendations. It would be safer, therefore preferable to use a grounded receptacle with the unit. GFCI would provide adequate grounding.”
If a microwave oven rated at 1000 watts needs a dedicated circuit, what about the toaster rated at 1600 watts, and the clothes iron rated at 1200 watts? What does the NEC specify (if anything) about these appliances found in most houses?


02:46AM | 11/24/02
Member Since: 11/05/01
101 lifetime posts
Do the instructions say "minimum 15 amp circuit"? Regardless this micro does not need a dedictade circuit. The NEC states installtions must be done according to manufacturers instructions. This is so that items are installed and used in the manner they were tested in order to obtain a listing. Your is a portable unit as to which I don't believe the NEC applies.


06:58AM | 11/25/02
Member Since: 11/18/02
30 lifetime posts
Regarding NEC 110.3.B (“according to manufacturers instructions”)
The Manual for this microwave oven says “For safety purposes this oven must be plugged into a 15 amp circuit. No other electrical appliances or lighting circuits should be on this line.” --- That sounds like an Individual Branch Circuit (NEC Definition and Exhibit 100.6).
But the Manual contradicts that by saying the oven “can easily be placed in … any room in your house”. So a consumer could follow the latter statement and adhere to NEC 110.3.B? Should this manufacturer need to change the Manual (I’m not sure either statement in their Manual is correct). Should their customer support be saying “GFCI would provide adequate grounding.” (GFCI is important to provide personal safety but does not by itself provide grounding).
Should any manufacturer state on the outside of the product carton if an Individual Branch Circuit is required, so the consumer knows that before the purchase?
The outside of this carton says “Listed for Household use only”. How much does it cost for a company to get a listing that says “for household use”? Could the consumer learn what product evaluations are needed that result in such a rating? Should the committee who stamps it as such get more involved and specify clearly that the product is listed for a NEC Individual Branch Circuit or whatever?
(The term “Household use” is not a NEC definition. The NEC 2002 revised definition of “Listed”, with all the associated terms, does not IMHO “help the user understand the approval process”; perhaps it’s talking about another approval process?)

The outside of this carton says “600 watts”. The Manual says “Rated Power Consumption 1000 watts, Microwave Output 600 watts”. If wattage is an important criteria (see below) which one of these are more important?

Back to the main question:
I see many statements by qualified persons that microwaves DO require a separate 20-amp circuit. My question is: What does the NEC say about these appliances? Does it say a “portable” unit does not need its own circuit? The word “portable” is not a NEC Definition; the closest I could find is “Cooking Unit, Counter-Mounted”. Is there a difference in the way Cooking Units utilize electricity compare with other appliances (ie. mixer, knife)? Does it depend on the wattage? If so, then a toaster rated at 1600 watts should be on a separate circuit? There should be specific, logical, and mistake-proof boundaries for safety. They should be clear and understandable to consumers, not just electrical contractors.


11:28AM | 11/27/02
Member Since: 11/02/02
72 lifetime posts
As far as "safety" is concerned, I'd think that so long as you aren't exceeding the amperage for which your circuit is rated, i.e. not blowing breakers all the time, that you are just fine. The dedicated branch circuit rule seems to me to be more of a convenience thing, to reduce the likelyhood of people getting frustrated as they buy new appliances. And who wants to buy a new house where the builder was so cheap as to not put enough circuits in the kitchen, right? Hence the NEC rule, is my guess.

We have an older house and our microwave, also a "portable" unit, is plugged into an outlet that is not the only outlet on the circuit. It's a 15-amp circuit. We never blow the breaker. No worries, in my opinion.

Someday, when I rewire the kitchen, I may well run a dedicated circuit for the microwave, but right now I'm not going to bother because I'm obviously not overloading my circuit.



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