Article 200 Use and Identification of Grounded Conductors
Article 210 Branch Circuits
Article 240 Overcurrent Protection
Article 300 Wiring Methods
Article 334 Nonmetallic-Sheathed Cable: Types NM, NMC and NMS
Article 362 Electrical Nonmetallic Tubing: Type ENT
Article 450 Transformers and Transformer Vaults
Color code for neutral conductors
Q: I am installing 208Y/120V and 480Y/277V, four-wire branch circuits in the same raceway. For the neutral conductors (grounded circuit conductors), I am using a white insulated conductor for the neutral on the 208V system and a gray insulated conductor for the neutral on the 480V system. The inspector has questioned this method of separate identification of the neutrals and suggested that I use white for one system and three white stripes on insulation that is not green for the other system. Is the color code I am using compliant with the NEC or must I change the colors as suggested by the inspector?
A: I assume the branch circuit conductor sizes are 6 AWG or smaller; therefore, the answer to your question should be in 200.6. The color of grounded circuit conductors (neutrals) of two different voltage systems is covered by 200.6(D). Part of this paragraph (D) reads: “Grounded Conductors of Different Systems. Where conductors of different systems are installed in the same raceway, cable, box, auxiliary gutter or other type of enclosure, one system grounded conductor, if required, shall have an outer covering conforming to 200.6(A) or 200.6(B). Each other system grounded conductor shall have an outer covering of white with a readily distinguishable, different-colored stripe other than green running along the insulation, or shall have other and different means of identification as allowed by 200.6(A) or (B) that will distinguish each system grounded conductor.”
It would appear that 200.6(D) requires one system grounded conductor to be white, gray or another color, but not green, with 3 continuous stripes. The other system grounded conductor must be white with a colored continuous stripe that is not green. However, the last part of 200.6(D) contains this phrase: “ ... or shall have other and different means of identification as allowed by 200.6 (A) or (B) that will distinguish each system grounded conductor.”
With the changes made in the 2002 edition of the NEC, white and gray are recognized as two different colors; therefore, one white neutral and one gray neutral satisfies the Code. These two colors should be easily identified, and that is the intent of the requirements.
There were 14 proposals to revise 200.6 for the 2005 edition of the NEC. Some were accepted by the Code-Making Panel. Some were editorial and others would allow gray marking at the terminal for 6 AWG and larger conductors whereas the present language limits the marking at grounded conductor terminals to white.
Although not required, signs or posters should be placed on each panelboard indicating the color of the grounded circuit conductor for each different voltage system. For example, “The circuit grounded conductor for 208Y/120V system is white,” and “The circuit grounded conductor for 480Y/277 system is gray.” This will help maintenance personnel and electricians when it is necessary to troubleshoot or do other work on the wiring.
Outlet box for wall-mounted lighting fixtures
Q: Is it necessary to provide outlet boxes for all luminaires (lighting fixtures)? Is it permissible to supply an exterior wall bracket lighting fixture by running nonmetallic sheathed cable through a hole in a brick wall without an outlet box, and using the lighting fixture canopy to contain the splices? A fixture strap is secured to the wall to support the lighting fixture.
A: It is not necessary to provide junction boxes for all types of lighting fixtures; however, the installation described does not satisfy National Electrical Code requirements.
Some luminaires (lighting fixtures) are permitted to be installed without outlet boxes. These include fluorescent luminaires, pole-mounted luminaires, cord-connected luminaries and portable floor and table lamps, to name a few.
An outlet box is required to comply with 300.15. The last paragraph in 300.15 requires an outlet box at each splice point for nonmetallic sheathed cable. And 334.12 does not permit nonmetallic sheathed cable in damp or wet locations. Any outdoor location exposed to the weather is a wet location.
Length of secondary conductors without overcurrent protection
Q: How far can secondary conductors be run from a transformer without providing overcurrent protection? The primary voltage is 480 and the secondary voltage is 208Y/120.
A: Overcurrent protection for the transformer is covered by 450.3(B) and Table 450-3(B). Secondary conductor overcurrent protection must comply with 240.21.
Where the primary overcurrent protective device does not exceed 125 percent of the primary full load current, secondary overcurrent protection for the transformer is not required. An allowance is made to go to the next larger standard size of fuse or circuit breaker where 125 percent of transformer full load current does not match any of the standard sizes shown in 240.6.
Secondary conductors can run for a distance of 10 feet from the secondary terminals of a transformer that does not require secondary overcurrent protection provided that the ampacity of the secondary conductors is equal to or greater than the load to be supplied. Overcurrent protection is provided for the tap conductors at the load end that does not exceed the ampacity of the conductors; and the conductors are enclosed in a raceway.
In industrial installations, secondary conductors can be 25 feet long under the following conditions: the ampacity of the conductors cannot be less than the secondary current rating of the transformer; the sum of the overcurrent device ratings does not exceed the ampacity of the secondary conductors; all secondary overcurrent devices are grouped; and the secondary conductors are protected from physical damage.
There is also a 25-foot rule for general application with different requirements. The secondary conductors must have an ampacity that, when multiplied by the ratio of the secondary-to-primary voltage, is at least one-third of the rating of the primary overcurrent device; the conductors terminate in a single circuit breaker or set of fuses that limit the current to the ampacity of the conductors; and the secondary conductors are protected from physical damage.
Finally, there is permission for an unlimited length of secondary conductors in 240.21(C)(4). For outdoor installations, there is no restriction on the length of secondary conductors where the conductors are protected from physical damage; a single circuit breaker or single set of fuses limit the load to the ampacity of the conductors; the overcurrent device is an integral part of the disconnecting means or is located immediately adjacent to the disconnect; the disconnecting means is located outside of the building or structure, or inside nearest the point of entrance, or the conductors are installed to comply with 230.6.
This discussion points out the variables that come into play as the lengths of secondary conductors change.
Nonmetallic sheathed cable in electrical metallic tubing
Q:Does the Code permit the installation of NM-B cable in an EMT sleeve to supply an air conditioning unit located on the roof of a building? The receptacle will be located within 10 feet of the air conditioner and the length of the electrical metallic tubing will be approximately 8 feet long.
A: I assume the receptacle outlet is being supplied to comply with 210.63 of the NEC. Unprotected locations exposed to the weather are classified as “wet.” Therefore, nonmetallic sheathed cable cannot be used as proposed. Under Uses Permitted in 334.10(A)(1) NM cable is allowed for concealed and exposed installations in normally dry locations. And 334.12(A)(10)d prohibits the use of NM cable where exposed to excessive moisture and dampness.
Although electrical metallic tubing is permitted as protection for nonmetallic sheathed cable in 334.15(B), and 300.15(C) provides some relief from the general installation requirements that apply to nonmetallic sheathed cable where installed in an EMT sleeve for physical protection, this cable cannot be used because any outdoor area exposed to the weather is a wet location as defined in Article 100 of the NEC, and nonmetallic sheathed cable is suitable for dry locations only.
Power supply to a receptacle for a microwave oven
Q:Does the Code allow one of the two small appliance branch circuits to supply a receptacle for a microwave oven located in a cabinet on the kitchen countertop in a dwelling unit?
A:Yes, one of the two required 20A branch circuits that supply the countertop receptacles in a dwelling unit may also supply receptacles located in appliance garages or cabinets.
The requirement for two or more 20A branch circuits for small appliances is found in 210.11(C) and spacing of receptacles supplied from these circuits is in 210.52(C). Part of item (5) in 210.52(C) which has the title “Receptacle Outlet Location.” contains this sentence: “Receptacle outlets rendered not readily accessible by appliances fastened in place, appliance garages, or appliances occupying dedicated space shall not be considered as these required outlets.”
Securing electrical nonmetallic tubing
Q:Does the National Electrical Code permit the securing of electrical nonmetallic tubing to metal studs with cable ties?
A:Yes, ENT supported and secured in this manner satisfies the requirements for securing and supporting as outlined in 362.30(A) and (B). Although part (A) requires fastening of ENT at least every 3 feet and within 3 feet of each termination, part (B) does not require fastening ENT every 3 feet where the tubing is supported by openings in framing members in horizontal runs, and the tubing is securely fastened within 3 feet of termination points. EC
FLACH, a regular contributing Code editor, is a former chief electrical inspector for New Orleans. He can be reached at 504.734.1720.