If you have a problem related to the National Electrical Code (NEC), are experiencing difficulty in understanding a Code requirement or are wondering why or if such a requirement exists, ask Charlie, and he will let the Code decide. Questions can be sent to firstname.lastname@example.org.
When neutral conductors can’t reach
If a neutral conductor in a panelboard is not long enough to reach the neutral bar, is a splice in a circuit breaker panel acceptable?
Yes, as long as you follow the requirements of NEC 312.8, where enclosures for switches or overcurrent devices are permitted to be used as junction boxes for conductors feeding through or tapping (splicing) off to other switches or overcurrent devices if adequate space is provided. The conductors must not fill the wiring space at any cross section to more than 40 percent of the cross-sectional area of the space, and the conductors, splices and taps are not permitted to fill the wiring space at any cross section to more than 75 percent of the cross-sectional area of that space.
I am finishing a 900-square-foot detached workshop (accessory building) in the backyard of our home. It is not clear whether tamper-resistant receptacles are required, as I’m getting conflicting answers. The building will be used exclusively as a woodworking workshop. While the building has a garage door, it is not a garage, and a car could not be parked in it because I will have some very large woodworking machines right inside the door that will be hooked up to permanently installed metal ductwork going to a cyclone dust collector.
The requirements for the use of tamper-resistant receptacles are shown in NEC 406.12, .13 and .14. These sections cover all areas where receptacles are specified in 210.52, in guest rooms and in child-care facilities. Your installation does not require tamper-resistant receptacles, but I might add that, since the difference in cost between tamper-resistant and nontamper-resistant receptacles is minimal, many installers are only carrying the tamper-resistant type rather than carrying two types of receptacles.
Three hots and one neutral
Where in the Code does it say three hots with one neutral must be on a three-pole, single-throw disconnect?
NEC 210.4(B) requires each multiwire branch circuit to be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates. If the multiwire circuit is a 4-wire circuit originating in a three-phase circuit-breaker panelboard, a three-pole circuit breaker can be used (or three single-pole circuit breakers with an identified handle tie as shown in 240.15(B)(1)). Multiwire circuits can present a danger to those working on equipment when all of the ungrounded conductors of a multiwire circuit may not be de-energized. This is particularly true when working on kitchen countertop receptacles that are split and fed from a multiwire circuit. Note that 210.4(D) contains requirements for grouping of conductors of a multiwire circuit within the panelboard.
Which way up?
Where does it say that receptacles cannot be installed face up? What about floor receptacles and show-window receptacles?
NEC 406.5(E) does not permit receptacles in a faceup position in countertops or similar work surfaces. Note this is a change from 406.4(E) in the 2008 Code. Listed floor boxes for use with receptacles are available for use in other areas. NEC 210.62 requires that at least one receptacle outlet be located within 18 inches of the top of the show window. This was presumably done to discourage the use of floor receptacles in show windows, although they are permitted.
Working clearance behind doors
What are the panelboard working clearance requirements for those mounted behind door swings?
The working clearances for panelboards installed behind door swings is the same as for panelboards installed elsewhere. NEC 110.26 requires working space the width of the equipment and at least a 90-degree opening of the panelboard doors. There is no NEC requirement relating to the swing of the door of the structure.
GFCI next to sinks
In other than a dwelling unit, where a countertop and sink (not a bathroom or kitchen) are provided, is a receptacle located next to a sink required to have ground-fault protection?
NEC 210.8(B)(5) requires ground-fault circuit interrupter (GFCI) protection for personnel where receptacles are installed within 6 feet of the outside edge of a sink. There are two exceptions to this requirement: industrial laboratories and patient bed locations.
Minimum size wire on starter
What is the procedure to calculate the minimum size wire on the load side of a starter that feeds a three-phase motor?
NEC 430.22 requires that conductors that supply a single motor shall have an ampacity of not less than 125 percent of the motor full-load current as determined by 430.6(A)(1), which requires that instead of using the actual current rating marked on the motor nameplate, the values given in Table 430.250 must be used for a three-phase motor. These values must be used to determine the ampacity of conductors and branch-circuit short circuit and ground-fault protection. Example: a 10 hp, three-phase, 230-volt motor as shown on Table 430.250 has a full-load current of 28 amperes (A). As required by 430.22, 28A 125% = 35A. This requires a 10 AWG conductor.
Uninsulated grounded conductor
Can the neutral service conductor be run as a bare copper conductor in a metal raceway?
NEC 230.41 Exception (1) permits a grounded conductor to be uninsulated where it is bare copper used in a raceway.
Loose communications cable
Could you please provide me with the standard violated when you have communications cable hanging loose from a conduit?
The requirement for supporting communications wires and cable is covered in 800.133(B). Communications wires and cables shall not be strapped, taped or attached by any means to the exterior of any raceway as a means of support.
Receptacles above suspended ceiling
Can receptacles be installed above a suspended ceiling?
Yes, but flexible cords cannot be installed above a suspended ceiling. NEC 400.8(5) does not permit flexible cords to be installed above suspended ceilings. Receptacles can be installed above suspended ceilings for use with flexible cords on maintenance tools or extension-cord lighting for maintenance purposes.
Does the Code permit fuse reducers?
Yes, 240.60(D) permits Class H cartridge fuses of the renewable type to be used only for replacement in existing installations where there is no evidence of overfusing or tampering. Class H fuses have an interrupting rating of 10,000A and are available in ampere ratings of 65 to 600A.
Code application by installation age
Does NEC 410.130(G) apply to new fixtures and retrofits or just new fixtures? If a ballast is being changed in an existing fixture, are wire nuts still sufficient or must a disconnect system be used?
Get up to date. The term “fixture” is not used in the NEC for attachment to lighting outlets. NEC 410.130(G)(1) applies to fluorescent luminaires installed in indoor locations in other than dwelling units. A disconnecting means, either internal or external, for the luminaire must be in place. A new sentence has been added in the 2011 Code that reads, “For existing installed luminaires without disconnecting means, at the time a ballast is replaced, a disconnecting means shall be installed.”
Two circuits, one receptacle
If I run a separate circuit for the refrigerator in a dwelling-unit kitchen, can I use a duplex receptacle?
NEC 210.52(B)(1) Exception No. 2 permits the receptacle outlet for refrigeration equipment to be supplied from an individual branch circuit rated 15A or greater. An individual branch circuit is defined as a branch circuit that supplies only one utilization device. A duplex receptacle is not permitted because it allows more than one utilization device to be supplied.
Specific voltage-drop requirements
Why doesn’t the Code have specific voltage-drop requirements?
The NEC in 90.1(C) tells us that the Code is not intended as a design specification, and it is left for the design people to specify voltage-drop considerations for their installations. However, the Code provides information in 210.19(A)(1) Informational Note No. 4 that relates to branch-circuit voltage drop and in 215.2(A)(3) Informational Note No. 2 for feeder conductors. In 695.7, the NEC requires voltage-drop considerations for fire pump installations, and in 647.4(D), for sensitive electronic equipment.
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