NEC Questions and Answers based on 2017 NEC^® - August 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 is the Code rule for GFCI protection of appliances?
A1. 422.5 Ground Fault Circuit Interrupter (GFCI) Protection [422.5]

(A) General. The following appliances rated not over 250V and 60A, single or three phase, must be GFCI protected.
(1) Automotive vacuum machines provided for public use. Figure 01
(2) Drinking water coolers, not drinking water dispensers.
(3) Cord-and-plug connected high pressure spray washing machines.
(4) Tire inflation machines provided for public use.
(5) Vending machines.

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

Q2. What are the NEC branch circuit rating requirements for individual appliances?
A2. (A) Individual Circuits [422.10]. The branch-circuit ampere rating for an individual appliance isn't permitted to be less than the branch-circuit rating marked on the appliance [110.3(B)]. The branch-circuit rating for motor-operated appliances must be in accordance with 430.6(A) and 430.22. A branch-circuit for an appliance that's a continuous load must be rated not less than 125 percent of the marked ampere rating of the appliance [210.19(A)(1)].

Example: What's the calculated load for conductor sizing for a 4,500W, 240V water heater?
Solution:
I = P/E
P = 4,500W
E = 240V
I = 4,500W/240V
I = 18.75A
Conductor Sizing = 18.75A × 125%
Answer: 23.44A, 10 AWG conductor [Table 310.15(B)(16)]

Branch circuits for household ranges and cooking appliances can be sized in accordance with Table 220.55 and 210.19(A)(3).

(B) Circuits Supplying Two or More Loads [422.10(B)]. Branch circuits supplying appliances and other loads must be sized in accordance with the following:

• Cord-and-plug-connected equipment must not be rated more than 80 percent of the branch-circuit ampere rating [210.23(A)(1)].
• Equipment fastened in place must not be rated more than 50 percent of the branch-circuit ampere rating, if the circuit supplies both luminaires and receptacles [210.23(A)(2)].
  

Q3. What are the NEC branch circuit overcurrent protection requirements for appliance circuits?
A3. (A) Branch Circuits. Branch-circuit conductors must have overcurrent protection in accordance with 240.4, and the overcurrent protection device rating must not exceed the rating marked on the appliance [422.11].
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(E) Nonmotor Appliances. The appliance overcurrent protection device must:
(1) Not exceed the rating marked on the appliance.
(2) Not exceed 20A if the overcurrent protection device rating isn't marked, and the appliance is rated 13.30A or less, or
(3) Not exceed 150 percent of the appliance rated current if the overcurrent protection device rating isn't marked, and the appliance is rated over 13.30A. Where 150 percent of the appliance rating doesn't correspond to a standard overcurrent protection device ampere rating listed in 240.6(A), the next higher standard rating is permitted.

Example: What's the maximum size overcurrent protection device for a 4,500W, 240V water heater?
Solution:
Protection Size = 4,500W/240V
Protection Size = 18.75A × 150%
Protection Size = 28A
Answer: 28A doesn't correspond to a standard ampere rating, so use 30A which is the next size up [240.6(A)].

Q4. What are the NEC branch circuit requirements for central heating equipment such as furnaces?
A4. An individual branch circuit must supply central heating equipment, such as gas, oil, or coal furnaces [422.12].

Author's Comment:
• This rule isn't intended to apply to a listed wood-burning fireplace with a fan, since the fireplace isn't central heating equipment.

Ex 1: Auxiliary equipment to the central heating equipment, such as pumps, valves, humidifiers, and electrostatic air cleaners, can be connected to the central heater circuit.

Author's Comment:
• Electric space-heating equipment must be installed in accordance with Article 424”Electric Space-Heating Equipment.

Ex 2: Permanently connected air-conditioning equipment can be connected to the individual branch circuit that supplies central heating equipment.

Q5. What are the NEC branch circuit requirements for storage water heaters?
A5. An electric water heater having a capacity of 120 gallons or less is considered a continuous load for the purpose of sizing branch circuits [422.13].

Author's Comment:
• Branch-circuit conductors must have a rating of at least 125 percent of the ampere rating of a continuous load [422.10] and the overcurrent protection is sized in accordance with 422.11(E)(3).