Article 100 Definitions
Article 110 Requirements for Electrical Installations
Article 210 Branch Circuits
Article 220 Branch-Circuit, Feeder and Service Calculations
Article 300 Wiring Methods
Article 310 Conductors for General Wiring
Article 450 Transformers and Transformer Vaults
Article 500 Hazardous (Classified) Locations, Classes I, II and III, Divisions 1 and 2
Article 505 Class I, Zone 0, 1 and 2 Locations
Article 518 Places of Assembly
Article 680 Swimming Pools, Fountains and Similar Installations
Fixed wiring in assembly spaces
In the February 2004 issue of ELECTRICAL CONTRACTOR, I answered a question about the use of nonmetallic raceways in places of assembly.
My answer was that nonmetallic raceways are permitted as the wiring method in some assembly occupancies where rigid nonmetallic conduit and nonmetallic tubing are concealed within walls, floors and ceilings that provide a thermal barrier with at least a 15-minute finish rating. This answer prompted a response from Erich Friend, vice president of engineering with Electro Acoustics and Video Inc., which is reproduced here because it points out some of the problems that may result when this wiring method is used.
“Your answer appeared to be technically correct and I do not dispute its accuracy. However, just because the NEC allows the use on nonmetallic raceways, doesn’t always make it a good practice. As you are aware, the selection of raceway materials addressed by the Code is concerned with safety, not signal fidelity. In my industry, audio/video systems integration, we frequently have electrical noise issues to work with.
“Although not required by Code in all circumstances, the use of steel raceways (not PVC, aluminum, or fiberglass) is almost mandatory for ‘Assembly Spaces.’ This is because most assembly spaces have audio and/or video systems and high-powered production lighting systems.
“Steel raceways affect our work in two ways: They shield the A/V systems wiring from external radiated electrical noise (where the A/V wiring is inside the raceways), and it contains and shields the radiated electrical noise from high harmonic content loads like those produced by phase-controlled dimming and HVAC motor controls. This second item is of significance around stages (platforms) where electronic musical instruments are used, as the less expensive products used by many performers tend to be highly susceptible to electrical noise interference.
“If a contractor is planning to use nonmetallic raceways in an assembly space or any facility that incorporates A/V and/or dimmed lighting systems, then they should be up front and clear about this decision to both the owner and the owner/architect’s A/V designer/integrator/contractor, as it can have a significant effect on the noise floor of the A/V systems.
“This can be a particularly important consideration when long raceway runs are situated parallel with A/V wiring and they are installed in proximity to each other.
“On a similar note, designers and contractors should be sensitive to the acoustic emissions of lamps and lamp ballasts, too. I can’t count the number of churches I’ve been in that have ‘parking lot’ HID fixtures installed and buzzing so loudly that you can’t carry on a conversation at normal levels. Returning back to the Latin origins of the word ‘Auditorium’ one finds the word to mean ‘Place to Hear.’ Just because the room is labeled ‘Chapel,’ ‘Sanctuary,’ ‘Great Hall,’
‘Fellowship Hall,’ ‘Gymnasium,’ or ‘Multipurpose Room,’ doesn’t mean it isn’t the ‘Auditorium.’ This is particularly true with school district sports facilities. Many build gymnasiums large enough to seat the entire school, but only build small theaters that seat a few hundred. In these facilities, the gymnasium is the ‘Auditorium,’ and it is used for all the school assemblies.
“Sometimes it’s prudent to ‘think outside the book.’”
Solid conductors in raceways
Q:Does the Code permit a solid 8 AWG copper conductor in a raceway?
A:Generally no, but there is an exception in 310.3. This part of the Code reads: “Stranded Conductors. Where installed in raceways, conductors in size 8 AWG and larger shall be stranded. Exception: As permitted or required elsewhere in this Code.” One example where an 8 AWG solid conductor is permitted in a raceway is found in 680.23(B)(2)(b). This part (b) allows an 8 AWG insulated solid copper conductor to be installed in nonmetallic conduit to supply a wet-niche lighting fixture in a swimming pool.
Q: Where in the National Electrical Code are the requirements for the reduction of neutral currents from nonlinear loads?
A: There is no requirement in the NEC for the reduction of neutral currents caused by nonlinear loads. There is a definition for a Nonlinear Load in Article 100 followed by a Fine Print Note that points out that electronic equipment, electric-discharge lighting, adjustable speed drives and similar electrical equipment as possible sources of harmonic currents. The neutral conductor for feeders and services is permitted to be reduced in ampacity for some loads, but there is no permission to reduce the ampacity of the neutral conductor in a 3-phase, 4-wire, wye-connected circuit that supplies nonlinear loads. This requirement appears in 220.22. The neutral is also considered to be a current carrying conductor on 4-wire, 3-phase, wye circuits where a major portion of the load is nonlinear; therefore, the circuit conductors must be derated to comply with 310.15. Exception 4 to 310.4 permits paralleling of neutral conductors in sizes 2 AWG and larger under engineering supervision where neutrals are overheating in existing installations. The Fine Print Note indicates that Exception 4 can be used to alleviate overheating of neutral conductors in existing installations due to high content of triplen harmonic currents.
There is also a Fine Print Note following 450.9, which deals with ventilation of transformers. Part of FPN No. 2 says: “Additional losses may occur in some transformers where nonsinusoidal currents are present resulting in increased heat in the transformer beyond its rating.”
GFCI receptacles in commercial kitchens
Q: A restaurant is designed so that the customers, after receiving their food, proceed to an area where they dispense their own carbonated beverages. Are these dispensing machines considered a part of the kitchen and required to be supplied from GFCI protected receptacles to comply with 210.8(B)(3)?
A: In my opinion the answer is no, but this is a judgment matter that has to be answered by the authority having jurisdiction. Since a commercial kitchen is not defined in Article 100—Definitions, or 210.8, the AHJ must decide if the dispensers are actually a part of the kitchen.
There are many interpretations of a commercial kitchen and these interpretations can be justified, but a clear definition is needed to provide uniform enforcement. Some relief is expected in the 2005 edition of the NEC with a definition of a kitchen appearing in 210.8(B). In the meantime, you may consider a commercial kitchen as an area where food for human consumption is prepared and cooked; there is a refrigerator, range, sink and countertop, plus any other kitchen countertop appliances that may be present.
Q:Is it the electrical inspector’s responsibility to classify hazardous areas in a refinery? Should the inspector define the boundaries of the Class I Division I and Class I Division 2 areas?
A:It is not the electrical inspector’s job to classify any hazardous areas, or the extent of these areas.
Documentation is required for all hazardous locations and is covered by 500.4. “Documentation. All areas designated as hazardous (classified) locations shall be properly documented. This documentation shall be applicable to those authorized to design, install, inspect, maintain, or operate electrical equipment at the location.” There are many Fine Print Notes in Articles 500 and 501 that list publications and other information that is useful to the electrical inspector.
In 505.7(A) this sentence appears: Classification of areas and selection of equipment and wiring methods shall be under the supervision of a qualified Registered Professional Engineer.”
Because the areas are already classified, the electrical inspector must make sure that the wiring and equipment meet the requirements for Class I, Division 1 or 2 as appropriate, nothing more.
Supporting nonmetallic sheathed cable
Q: Am I allowed to support several nonmetallic-sheathed cables that are properly derated and bundled together with a cable tie that is then secured by a staple driven into a stud? Is this an acceptable means of support?
A: Yes, provided that the cables are not damaged. Nonmetallic-sheathed cable is permitted to be secured by staples, cable ties, straps, hangars or similar fittings. The bundled cables must be installed so that the cables are at least 1.25 inches from the edges of the stud as required by 300.4. Finally, do not forget 110.12, which requires the cable to be installed in a neat and workmanlike manner. EC
FLACH, a regular contributing Code editor, is a former chief electrical inspector for New Orleans. He can be reached at 504.734.1720.