NEC Questions and Answers based on 2017 NEC^® - October 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.

Q1. What are the NEC requirements for sizing branch circuits for fixed electric space-heating equipment?
A1. Branch-Circuit Sizing. For the purpose of sizing branch-circuit conductors, fixed electric space-heating equipment and motor(s) are to be considered a continuous load [424.3(B)].

Author’s Comment:
• The branch-circuit conductors and overcurrent protection devices for fixed electric space-heating equipment must have an ampacity not less than 125 percent of the total heating load [210.19(A)(1) and 210.20(A)].

Example: What size conductor and overcurrent protection device are required for a 9,600 kW, 240V fixed electric space heater that has a 3A blower motor with 60°C terminals? Figure 01
Solution:
Step 1: Determine the total load:

I = W/E
I = 9,6000 VA/240V
I = 40A + 3A = 43A

Step 2: Size the conductors at 125 percent of the total current load [110.14(C)(1), 210.19(A)(1), and Table 310.15(B)(16)]:

Conductor = 43A × 1.25
Conductor = 53.75A, 6 AWG, rated 55A at 60°C

Step 3: Size the overcurrent protection device at 125 percent of the total current load [210.20(A), 240.4(B), and 240.6(A)]:

Overcurrent Protection = 43A × 1.25
Overcurrent Protection = 53.75A, next size up is 60A

Answer: Use a 6 AWG conductor and 60A overcurrent protection device.

Q2. What does the Code allow in regard to receptacle outlets installed on permanently installed baseboard electric heaters?
A2. If a permanently installed electric baseboard heater has factory-installed receptacle outlets, the receptacles aren’t permitted to be connected to the heater circuits [424.9].

Informational Note: Listed baseboard heaters include instructions that prohibit their installation below receptacle outlets.

Q3. What is the Code rule regarding disconnects for fixed electric space heating equipment?
A3. Means must be provided to simultaneously disconnect the heater, motor controller, and supplementary overcurrent protection devices of all fixed electric space-heating equipment from all ungrounded conductors [424.19].

Heating Equipment Without Supplementary Overcurrent Protection. For fixed electric space-heating equipment, the branch-circuit circuit breaker can serve as the disconnect if the circuit breaker is within sight from the heater or it’s capable of being locked in the open position [424.19(B)].

Unit Switch as Disconnect. A unit switch with a marked “off” position that’s an integral part of the equipment can serve as the heater disconnect, if it disconnects all ungrounded conductors of the circuit [424.19(C).

Q4. What is the GFCI requirement in the Code for electric space-heating cables?
A4. GFCI Protection. GFCI protection for personnel is required for electric space-heating cables that are embedded in concrete or poured masonry floors of bathrooms and kitchens, and hydromassage bathtub locations [424.44(E)].

Author’s Comment:
• See 680.27(C)(3) for restrictions on the installation of radiant-heating cables for spas and hot tubs installed outdoors [680.40].

Q5. What does the NEC require regarding disconnects for duct heaters?
A5. The disconnect for the duct heater must be accessible and be installed at or within sight from the controller [424.65].

Author’s Comment:
• Where the disconnecting means is not within sight of the controller the disconnecting means must be capable of being locked in the open position [424.19(A)].