NEC Questions and Answers based on 2017 NEC^® - September 2019

Figure 01

For EC&M Magazine
By Mike Holt, NEC^® Consultant
Here's the follow-up to yesterday's newsletter. This includes the answers to the questions sent, so you can see how you did.

Note: The answers to these questions are based on the 2017 NEC. Underlined text denotes a change in the 2017 NEC.

Q1. What are the NEC branch circuit requirements for central vacuums?
A1. (A) Circuit Loading. Listed central vacuum systems must be on a separate circuit if the rating of the equipment exceeds 50 percent of the ampere rating of the circuit [210.23(A)(2) and 422.15].

Author’s Comment:
• 210.23(A)(2) specifies that equipment fastened in place, other than luminaires, must not be rated more than 50 percent of the branch-circuit ampere rating if this circuit supplies both luminaires and receptacles. Due to this requirement, a separate 15A circuit is required for a central vacuum receptacle outlet if the rating of the central vacuum exceeds 7.50A. A separate 20A circuit is required for a central vacuum receptacle outlet if the rating of the central vacuum exceeds 10A, but not 16A [210.23(A)(2)].  

Q2. In general, when does the Code allow flexible cords to be used for the connection of appliances?
A2. (A) General. Flexible cords are permitted to [422.16(A)]:

(1) Facilitate frequent interchange, or to prevent the transmission of noise and vibration [400.10(A)(6) and 400.10(A)(7)].

(2) Facilitate the removal of appliances fastened in place, where the fastening means and mechanical connections are specifically designed to permit ready removal [400.12(A)(8)].

Author’s Comment:
• Flexible cords aren’t permitted to be used for the connection of water heaters, furnaces, and other appliances fastened in place, unless the appliances are specifically identified to be used with a flexible cord.

Q3. What are the Code rules for the connection of dishwashers and trash compactors by means of flexible cords?
A3. (B) Specific Appliances [422.16(B)].

(1) In Sink Waste Disposal. A flexible cord is permitted for an in sink waste disposal if:

(1) The flexible cord has a grounding type attachment plug.

Ex: A listed in sink waste disposal marked as protected by a system of double insulation isn’t required to be terminated with a grounding type attachment plug.

(2) The flexible cord length is at least 18 in. in length and no longer than 3 ft.

(3) The receptacle must be located so as to protect against damage to the flexible cord.

(4) The receptacle is accessible.

(2) Dishwashers and Trash Compactors. A flexible cord is permitted for a dishwasher or trash compactor if:

(1) The flexible cord has a grounding type attachment plug.

Ex: A listed dishwasher or trash compactor marked as protected by a system of double insulation isn’t be required to be terminated with a grounding type attachment plug.

(2) For a trash compactor, the flexible cord length is at least 3 ft in length and not longer than 4 ft, measured from the rear plane of the appliance.

(3) For a built in dishwasher, the length of the flexible cord is at least 3 ft and not longer than 6 ft 6 in., measured from the face of the attachment plug to the plane of the rear of the appliance.

(4) For a dishwasher or trash compactor, the receptacle must be located so as to protect against damage to the flexible cord.

(5) The receptacle for the trash compactor must be located in the space occupied by the trash compactor or in the space adjacent to the trash compactor.

(6) The receptacle for a built in dishwasher must be located in the space adjacent to the space occupied by the dishwasher.

(3) Wall Mounted Ovens and Counter Mounted Cooking Units. Wall mounted ovens and counter mounted cooking units can be cord
and plug connected for ease in servicing or installation.

(4) Range Hoods. Range hoods can be cord and plug connected if all of the following conditions are met:

(1) The flexible cord for the range hood terminates with a grounding
type attachment plug.

Ex: A listed range hood marked as protected by a system of double insulation isn’t required to be terminated with a grounding type attachment plug.

(2) The length of the flexible cord for the range hood isn’t permitted to be less than 18 in. or longer than 48 in.

(3) The receptacle for the range hood must be located so as to protect against physical damage to the flexible cord.

(4) The range hood receptacle must be accessible.

(5) The range hood receptacle must be supplied by an individual branch circuit.

Q4. What does the Code require for the support of ceiling paddle fans?
A4. Ceiling paddle fans must be supported independently of an outlet box or by one of the following [422.18]:

(1) A listed outlet box or listed outlet box system must be marked as suitable for ceiling paddle fan support of not more than 70 lb. Outlet boxes for a ceiling paddle fan that weighs more than 35 lb must include the maximum weight to be supported in the required marking in accordance with 314.27(C).

(2) A listed outlet box system, a listed locking support and mounting receptacle, and a compatible factory installed attachment fitting designed for support, identified for the use, and installed in accordance with 314.27(E).

Q5. What are the NEC rules for the disconnecting means of appliances?
A5. Each appliance must have a means that disconnects simultaneously all ungrounded circuit conductors [422.30].

Permanently Connected Appliance Disconnects [422.31]

(A) Appliances Rated at Not Over 300 VA or 1⁄8 Horsepower. For 300 VA or 1⁄8 horsepower or less appliances, a circuit breaker located within sight from the appliance, or is lockable with provisions for locking to remain in place whether the lock is installed or not in accordance with 110.25, can serve as the disconnect means.

(B) Appliances Rated Over 300 VA. For appliances rated over 300 VA, a switch or circuit breaker located within sight of the appliance, or is lockable with provisions for locking to remain in place whether the lock is installed or not in accordance with 110.25, can serve as the disconnect means.Figure 01 

Author’s Comment:
• According to Article 100, “Within Sight” means that it’s visible and not more than 50 ft from one to the other.

(C) Motor Operated Appliances Rated Over 1⁄8 Horsepower. For motor operated appliances rated over 1⁄8 horsepower, the disconnect must be located within sight from the motor operated appliance or be lockable with provisions for locking to remain in place whether the lock is installed or not in accordance with 110.25.

Ex: An appliance containing a unit switch that complies with 422.34.

(A) Attachment Plug and Attachment Fitting. Cord and plug or attachment fitting connected appliances can serve as the disconnecting means [422.33].

(B) Cord and Plug Connected Ranges. A plug and receptacle of a cord and plug connected household electric range accessible from the front of the range by the removal of a drawer meets the disconnecting means requirements of 422.33(A).