NEC Questions and Answers based on 2020 NEC^® - October 2021

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 2020 NEC.

Q1. What are the NEC requirements for GFCI protection of appliances?
A1. GFCI Protection [422.5]

(A) General. The following appliances rated 150 volts-to-ground or less and 60A or less must be GFCI protected by Class “A” protective device(s).
(1) Automotive vacuum machines. 
(2) Drinking water coolers and bottle fill stations.
(3) Cord-and-plug-connected high-pressure spray washing machines.
(4) Tire inflation machines. 
(5) Vending machines.
(6) Sump pumps. 
(7) Dishwashers.

Note: Section 210.8 specifies requirements for GFCI protection for the receptacle outlets where the location warrants such protection.

(B) Type and Location. The GFCI must be readily accessible and located in one or more of the following locations: 
(1) A GFCI circuit breaker,
(2) A GFCI device or receptacle,
(3) A GFCI integral with the attachment plug,
(4) A GFCI within the supply cord not more than 12 in. from the attachment plug, or
(5) A factory installed GFCI within the appliance. 

Q2. What is the NEC requirement for the listing of appliances?
A2. Listing Required [422.6]
Appliances supplied by 50V or higher must be listed.

Q3. What is the Code requirement for branch circuit sizing for appliances?
A3. Branch Circuits [422.10]
(A) Individual Branch Circuits. The ampacities of branch-circuit conductors for an individual appliance are not permitted to be less than the branch-circuit rating marked on the appliance.

Author’s Comment:
►Listed appliances come with installation instructions from the manufacturer, and sometimes the minimum overcurrent protection and or conductor size are marked on the appliance.

Branch-circuit conductors for household ranges and cooking appliances are sized in accordance with Table 220.55 and 210.19(A)(3).

(B) Branch Circuits Supplying Two or More Loads. Branch circuits supplying appliances in addition to other loads must be sized in accordance with 210.23(A) as follows:

• A 15A or 20A branch circuit cord-and-plug-connected equipment is not permitted to be rated more than 80 percent of the branch-circuit ampere rating [210.23(A)(1)].
• A 15A or 20A branch circuit equipment fastened in place is not permitted to be rated more than 50 percent of the branch-circuit ampere rating, if the circuit supplies both luminaires and receptacles [210.23(A)(2)].
  

Q4. What is the Code requirement for sizing the overcurrent device and conductors for an electric water heater with a capacity of 120 gallons or less?
A4. The branch-circuit overcurrent device and conductors for fixed storage-type water heaters that have a capacity of 120 gallons or less must be sized not smaller than 125 percent of the rating of the water heater [422.13].  

Example
Question: What size conductor and overcurrent protection are required for a 4,500W, 240V water heater, having a wiring method or Type NM cable? Figure 01
(a) 20A/12 AWG   (b) 25 or 30A/10 AWG   (c) 40A/8 AWG   (d) 50A/6 AWG
Answer: (b) 30A/10 AWG

Solution:
Step 1: Determine the branch-circuit rating [ 422.13].
Circuit Current = 4,500W/240V
Circuit Current = 18.75A
Circuit Rating = 18.75A × 125%
Circuit Rating = 23.44A
Circuit Conductor = 10 AWG rated 30A at 60°C [110.14)(C)(1)(a)(2), 334.80, and Table 310.16]
Step 2: Determine the overcurrent protection rating [ 422.13].
Circuit Current = 4,500W/240V
Circuit Current = 18.75A
Circuit Protection = 18.75A × 125%
Circuit Protection = 23.44A, use next size up: 25A [240.6(A)]

Note: 422.11(E)(3) permits the overcurrent protective device to be sized up to 150% of the appliance rating.
Circuit Protection = 18.75A × 150%
Circuit Protection = 28.75A, use next size up: 30A [240.6(A)]

Q5. When does the NEC permit the connection of appliances by means of flexible cords?
A5. Flexible cords are permitted for appliances when needed for [422.16(A)]:

(1) Facilitating frequent interchange, or to prevent the transmission of noise and vibration [400.10(A)(6) and 400.10(A)(7)].
(2) Facilitating the removal of appliances fastened in place, where the fastening means and mechanical connections are specifically designed to permit ready removal [400.10(A)(8)].

Author’s Comment:
►Flexible cords are not permitted 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.