NEC Questions and Answers based on 2008 NEC
January 2010 Part 2

By Mike Holt for EC&M Magazine

Here’s the follow up to yesterday’s newsletter. This includes all of the answers to the questions sent, so you can see how you did.

Q1. What are the rules for the location of the service disconnect?
A1. Section 230.70 contains the rules as follows: The service disconnecting means must open all service-entrance conductors from the building or structure premises wiring.
(A) Location.
(1) Readily Accessible. The service disconnecting means must be placed at a readily accessible location either outside the building or structure, or inside nearest the point of service conductor entry.

Warning: Because service-entrance conductors don’t have short-circuit or ground-fault protection, they must be limited in length when installed inside a building. Some local jurisdictions have a specific requirement as to the maximum length permitted within a building.

(2) Bathrooms. The service disconnecting means is not permitted to be installed in a bathroom.

Note: Overcurrent devices must not be located in the bathrooms of dwelling units, or guest rooms or guest suites of hotels or motels [240.24(E)].

(3) Remote Control. Where a remote-control device (such as a pushbutton for a shunt-trip breaker) is used to actuate the service disconnecting means, the service disconnecting means must still be at a readily accessible location either outside the building or structure, or nearest the point of entry of the service conductors as required by 230.70(A)(1).

Note:
•   See the definition of “Remote Control” in Article 100.
•   The service disconnecting means must consist of either a manually operated switch, or a power-operated switch or circuit breaker also capable of being operated manually [230.76].

(B) Disconnect Identification. Each service disconnecting means must be permanently marked to identify it as part of the service disconnecting means.

Note: When a building or structure has multiple services and/or feeders, a plaque is required at each service or feeder disconnect location to show the location of the other service or feeder disconnect locations. See 230.2(E).

Q2. In a commercial kitchen, does the 20A, 125V refrigerator receptacle outlet need to be GFCI protected?
A2. All 15A and 20A, 125V receptacles installed in an area with a sink and permanent facilities for food preparation and cooking [Article 100], even those that don’t supply the countertop surface, must be GFCI protected [210.8(B)(2)].

Q3. Is there any requirement to install cages or lamp tubes on surface mount fluorescent fixtures?
A3. No, there is no such requirement in the NEC.

Q4. What are the feeder conductor requirements when wiring a pool house?
A4. See 680.25:
(A) Wiring Methods. Feeder conductors to panelboards containing permanently installed pool, outdoor spa, or outdoor hot tub equipment circuits must be installed in rigid metal conduit, intermediate metal conduit, liquidtight flexible nonmetallic conduit, or PVC conduit. Electrical metallic tubing is permitted where installed on or within a building, and electrical nonmetallic tubing is permitted where installed within a building.

Exception: Branch circuits for permanently installed pool, outdoor spa, or outdoor hot tub equipment can originate from an existing panelboard where the existing feeder contains an equipment grounding conductor within the outer sheath of a cable.

(B) Equipment Grounding Conductor. An insulated copper or aluminum equipment grounding conductor must be installed with the feeder conductors between the grounding terminal of the pool, outdoor spa, or outdoor hot tub equipment panelboard and the grounding terminal of the applicable service equipment.
(1) Size. This feeder equipment grounding conductor must be sized according to 250.122, but not smaller than 12 AWG.
(2) Separate Buildings. Where a feeder is run to a separate building or structure to supply permanently installed swimming pool, outdoor spa, or outdoor hot tub equipment, an insulated equipment grounding conductor must be installed with the feeder conductors to the disconnecting means at the separate building or structure [250.32(B)].

Q5. I have equipment that draws 104A and runs for more than 3 hours continuously. The machine requires a neutral, with a load of 18A. The equipment has an integral panelboard in it, with a 125A main. How do I size the neutral conductor for this equipment?
A5. The feeder neutral conductor must be sized to carry the maximum unbalanced load, in accordance with 220.61, and must not be smaller than the size listed in 250.122, based on the rating of the feeder overcurrent device [215.2(A)(1)]. In this application, a 12AWG conductor would carry the load, but would not satisfy the requirement that the conductor be as large as indicated in 250.122. According to 250.122, a 6AWG neutral conductor would be required, based on the rating of the feeder overcurrent device of 125A.

Q6. Can I use SER cable in a four story multifamily dwelling?
A6. NM and SE cables can only be used in multifamily dwellings permitted to be of Types III, IV, and V construction [334.10(A) and 338.10(B)(4)(a)]. The number of stories does not enter into the requirements. Types of construction are covered in the applicable building (such as the International Building Code), and are not covered in the NEC. Type of construction, in a nutshell, is the types of material that a building can be constructed of, such as wood, concrete and steel. Because this is a difficult topic for electricians to deal with, your best bet is to consult the building official of the city/county that you are working in.

Q7. Can you please go over the feeder tap rules?
A7. Certainly. These rules are found in 240.21(B), and are different depending on the length of the feeder taps.
(1) 10-Foot Feeder Tap. Feeder tap conductors up to 10 ft long are permitted without overcurrent protection at the tap location if installed as follows:
(1)  The ampacity of the tap conductor must not be less than:

a.  The calculated load in accordance with Article 220, and
b.  The rating of the device or overcurrent device supplied by the tap conductors.

(2)  The tap conductors must not extend beyond the equipment they supply.
(3) The tap conductors must be installed in a raceway if they leave the enclosure.
(4)  The tap conductors must have an ampacity not less than 10 percent of the ampacity of the overcurrent device that protects the feeder.
FPN: See 408.36 for the overcurrent protection requirements for panelboards.

(2) 25-Foot Feeder Tap. Feeder tap conductors up to 25 ft long are permitted without overcurrent protection at the tap location if installed as follows:
(1)  The ampacity of the tap conductors must not be less than one-third the ampacity of the overcurrent device that protects the feeder.
(2)  The tap conductors terminate in a single circuit breaker, or set of fuses rated no more than the tap conductor ampacity in accordance with 310.15 [Table 310.16].
(3)  The tap conductors must be protected from physical damage by being enclosed in a manner approved by the authority having jurisdiction, such as within a raceway.

(3) Taps Supplying a Transformer. Feeder tap conductors that supply a transformer must be installed as follows:
(1)  The primary tap conductors must have an ampacity not less than one-third the ampacity of the overcurrent device.
(2)  The secondary conductors must have an ampacity that, when multiplied by the ratio of the primary-to-secondary voltage, is at least one-third the rating of the overcurrent device that protects the feeder conductors.
(3)  The total length of the primary and secondary conductors must not exceed 25 ft.
(4)  Primary and secondary conductors must be protected from physical damage by being enclosed in a manner approved by the authority having jurisdiction, such as within a raceway.
(5)  Secondary conductors must terminate in a single circuit breaker, or set of fuses rated no more than the tap conductor ampacity in accordance with 310.15 [Table 310.16].

(5) Outside Feeder Taps of Unlimited Length. Outside feeder tap conductors can be of unlimited length, without overcurrent protection at the point they receive their supply, if installed as follows:
(1)  The tap conductors must be suitably protected from physical damage in a raceway or manner approved by the authority having jurisdiction.
(2)  The tap conductors must terminate at a single circuit breaker or a single set of fuses that limits the load to the ampacity of the conductors.
(3)  The overcurrent device for the tap conductors must be an integral part of the disconnecting means, or it must be located immediately adjacent to it.
(4)  The disconnecting means must be located at a readily accessible location, either outside the building or structure, or nearest the point of entry of the conductors.

Q8. If I run PVC between the meter and service disconnect, is an equipment grounding conductor required?
A8. At service equipment, the service neutral conductor provides the effective ground-fault current path to the power supply [250.24(C)]; therefore, an equipment grounding conductor isn’t required to be installed within PVC conduit containing service-entrance conductors [250.142(A)(1) and 352.60 Ex 2].