Motor-Operated Appliances

By Mark C. Ode | Mar 15, 2003
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Article 422 of the 2002 National Electrical Code covers electrical appliances used in dwellings, commercial facilities and some industrial installations. Many appliances utilize only electrical power. However, some use other power sources—such as natural gas, propane, or other hydrocarbon fuels—to provide the fuel source for the appliance and only use electrical power within the appliance for a blower motor, electric ignition of the fuel source, or control voltage.

An appliance is defined in Article 100 as utilization equipment, generally other than industrial, that is normally built in standardized sizes or types and is installed or connected as a unit to perform one or more functions, such as clothes washing, air conditioning, food mixing, deep frying, and so forth.

Article 422 is comprised of five parts, with Part I dealing with general requirements. Part II provides the requirements for the installations of appliances and Part III covers the disconnecting means requirements for appliances. Construction requirements for appliances can be found in Part IV and marking of appliances is located in Part V.

An electrician installing a circuit for an appliance connection must read Article 422 very carefully to completely understand the requirements for this circuit. It is especially critical where those appliances contain either a motor or a compressor as the only electrical component in the appliance. While Article 422 may apply generally, other articles may apply more specifically to the installation. For example, a natural gas forced-air heating unit would seem to be covered by Article 422, but is actually covered in other areas of the NEC as indicated in Article 422.

The first step in installing a motor-operated appliance is to determine if only Article 422 covers the appliance or if Article 430 can be used for the installation. Section 422.3 states that the requirements of Article 430 shall apply to the installation of motor-operated appliances except as specifically amended by Article 422. If appliances contain a hermetic refrigerant motor-compressor, then the requirements of Article 440 shall apply to the installation of appliances, as amended specifically within Article 422.

Section 422.10 covers the ratings of branch circuits capable of carrying appliance current without overheating. Section 210.3 provides information on the rating of a branch circuit as the maximum permitted ampere rating or setting of the overcurrent devices protecting the branch circuit. Individual branch circuits are those branch circuits that supply a single piece of utilization equipment. Multiple receptacles, loads or equipment are supplied by non-individual branch circuits.

The rating of an individual appliance branch circuit shall not be less than the marked rating of the appliance or the marked rating of an appliance having combined loads consisting of motors and other loads, as provided in 422.62. If the load is a motor-operated appliance and does not have a rating marked on the appliance, the rating of the branch circuit must be in accordance with Part II of Article 430, not Article 422.

Part II of Article 430 requires the conductors supplying a single motor used in a continuous duty application to be sized at not less than 125 percent of the motor’s full-load current rating based on Tables 430.147 through 430.150. The appliance branch circuit must have a rating of not less than the rating of the conductors.

The branch-circuit rating for an appliance that is continuously loaded for three hours or more, other than a motor-operated appliance, shall not be sized less than 125 percent of the marked rating on the appliance, or not less than 100 percent of the marked rating if the branch-circuit device and its assembly are listed for continuous loading at 100 percent of its rating.

Section 422.3 must again be followed to determine a disconnecting means for the motor-operated appliance. Since 422.3 states that a motor-operated appliance must comply with the requirements in Article 430, unless specifically amended by Article 422, a thorough reading of Part III of Article 422 will provide any specific requirements for the disconnecting means.

Section 422.33 permits an appliance to use a cord-and-plug-connection as the disconnecting means for the appliance, if the separable connector or the receptacle is accessible to permit easy access for disconnecting the appliance. If they are not accessible, then an additional disconnecting means must be installed.

Section 430.109(F) permits the cord-and-plug connection as the disconnecting means of a motor where a horsepower-rated attachment plug and receptacle are used and the horsepower rating is not less than the rating of the motor. The disconnecting means for a natural gas forced air-heating unit, as mentioned in the fourth paragraph above, could be a horsepower-rated cord, plug, and receptacle.

A thorough understanding of the NEC will assist an installer in providing a Code- compliant installation and will ensure the ability to safely disconnect motor-operated appliances. EC

ODE is a staff engineering associate at Underwriters Laboratories Inc., in Research Triangle Park, N.C. He can be reached at 919.549.1726 or at [email protected].

About The Author

ODE is a retired lead engineering instructor at Underwriters Laboratories and is owner of Southwest Electrical Training and Consulting. Contact him at 919.949.2576 and [email protected]

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