Article 300 Wiring Methods; Article 310 Conductors for General Wiring; Article 410 Luminaires, Lampholders, and Lamps; Article 440 Air-Conditioning and Refrigerating Equipment; Article 517 Health Care Facilities; Article 680 Swimming Pools, Fountains, and Similar Installations; Article 700 Emergency Systems
Underground wet locations
Section 300.5(C) states, “Cables and insulated conductors installed in enclosures or other raceways in underground installations shall be listed for use in wet locations.” Why doesn’t this requirement simply reference 310.8(C) instead of just one part of 310.8(C)?
This change now indicates that both insulated conductors and cables in underground installations must be listed for use in a wet location and also must comply with 310.8(C). This change actually occurred at the comment stage for the 2008 National Electrical Code (NEC) as part of a revision, and since new information could not be added without public review, the conductors and cables must be both listed for wet locations, as noted in the 2005 NEC, and must comply with 310.8(C), as changed for the 2008 NEC. Section 300.5(B) now states, “The interior of enclosures or raceways installed underground shall be considered to be a wet location. Insulated conductors and cables installed in these enclosures or raceways in underground installations shall be listed for use in wet locations and shall comply with 310.8(C). Any connections or splices in an underground installation shall be approved for wet locations.”
Above-ground wet locations
Is the NEC clear that a raceway on the outside of a building, where subject to rain, is in a wet location and that the conductors inside the raceway are required to be listed or identified as being suitable for a wet location?
Section 300.9 in the 2008 NEC now spells this out very clearly. The new section states, “Where raceways are installed in wet locations above grade, the interior of these raceways shall be considered to be a wet location. Insulated conductors and cables installed in raceways in wet locations above grade shall comply with 310.8(C).” Code--Making Panel 3 inserted this new Section 300.9 to clarify that the interiors of raceways installed above grade in wet locations are wet locations, and insulated conductors and cables installed within the raceways must comply with 310.8(C). Condensation and leakage around raceway fittings can subject the conductors to a wet condition.
Hydromassage tub bonding
Some jurisdictions require the 8 AWG copper bonding conductor used to bond the pump and other metallic piping of a hydromassage bathtub to be run back to the service or panelboard where the pump branch circuit originates or the 8 AWG bonding conductor from the hydromassage bathtub equipment be connected to the closest grounding electrode. Is this required by the National Electrical Code?
The bonding conductor does not need to be “run back” to anywhere. A new last sentence in the 2008 NEC clarifies the bonding requirements for hydromassage bathtubs. Bonding applies to all metal piping systems and all grounded metal parts in contact with the circulating water of the hydromassage tub. Section 680.74 states, “The 8 AWG or larger solid copper bonding jumper shall be required for equipotential bonding in the area of the hydromassage bathtub and shall not be required to be extended or attached to any remote panelboard, service equipment, or any electrode.”
A design shows two emergency generators installed in parallel and connected to a single 1,200-ampere, 277/480-volt outdoor switchboard at a hospital. The switchboard is a three-section with an overcurrent protective device in the first section supplying a critical branch transfer switch; an overcurrent protective device in the second section supplying the hospital life safety branch transfer switch; and three overcurrent protective devices in the third section supplying a hospital equipment system transfer switch, a transfer switch for legally required standby loads and a transfer switch for optional standby loads. There is a load pickup and shedding system for the switchboard. Is this a Code-compliant design based on the switchboard separation requirements?
Section 517.26 for essential electrical systems for healthcare facilities requires compliance with Article 700 for emergency systems, unless amended by the requirements in Article 517. The requirements for the separation of emergency (Article 700), legally required standby (Article 701), and optional standby overcurrent protective devices and conductors (Article 702) have been clarified in the 2008 NEC by adding new 700.9(B)(5) permitting wiring from an emergency source of power to supply any combination of emergency, legally required, and optional loads as long as the requirements in 700.9(B)(5) are followed.
The important text of this requirement is that wiring from an emergency source or emergency source distribution overcurrent protection to emergency loads shall be kept entirely independent of all other wiring and equipment, unless otherwise permitted in 700.9(B)(1) through (5). New (5) covers wiring from an emergency source to supply any combination of emergency, legally required, or optional loads in accordance with (a), (b) and (c) to be as follows:
“(a) From separate vertical switchboard sections, with or without a common bus, or from individual disconnects mounted in separate enclosures;
“(b) The common bus or separate sections of the switchboard or the individual enclosures shall be permitted to be supplied by single or multiple feeders without overcurrent protection at the source
“Exception to (5)(b): Overcurrent protection shall be permitted at the source or for the equipment, provided the overcurrent protection is selectively coordinated with the down-stream overcurrent protection.
“(c) Legally required and optional standby circuits must not originate from the same vertical switchboard section, panelboard enclosure, or individual disconnect enclosure as emergency circuits.”
Hermetic refrigerant motor compressors
Where an individual hermetic motor-compressor has a full-load current of 32 amps, and 175 percent of this rating is used to establish the overcurrent protection for the motor (32 × 175% = 56), is it permissible to round up to a 60-ampere overcurrent protective device, or must the device rating be sized at the next lower standard size overcurrent protective device? Where the motor-compressor will not start with the 175 percent rated overcurrent protective device, is it permissible to size the overcurrent protective device at a higher ampere rating?
A hermetic refrigerant motor-compressor- must be provided with a nameplate that indicates the manufacturer’s name, trademark or symbol; identifying designation; phase; voltage; and frequency. The rated-load current in amperes of the motor-compressor also must be marked by the equipment manufacturer on either or both the motor-compressor nameplate and the nameplate of the equipment in which the motor-compressor is used. The marked value must be used for sizing the overcurrent protective device, since high head pressure during a very hot day or a higher head pressure caused by an overcharged refrigerant level can cause the refrigerant pressure to also rise, resulting in more current for the unit.
Where the motor-compressor will not start at the 175 percent level, Section 440.22(A) permits the motor-compressor branch-circuit short-circuit and ground-fault protective device to be sized large enough to be capable of carrying the starting current of the motor. A protective device having a rating or setting not exceeding 225 percent of the motor-compressor rated-load current or branch-circuit selection current, whichever is greater, is permitted. However, where the protection specified is not sufficient for the starting current of the motor, the rating or setting shall be permitted to be increased but shall not exceed 225 percent of the motor rated-load current or branch-circuit selection current, whichever is greater. Standard ampere ratings for overcurrent devices are listed in 240.6.
• (If not sufficient for the starting current of the motor, then can use up to 225%) 32A x 225% = 72A
• (Shall not exceed 225 percent) 70A overcurrent device maximum
LEDs in closets
Many builders are now using LED lighting in clothes closets in dwellings. Have there been any minimum clearances established between LED-type luminaires and the nearest point of storage space in a clothes closet?
Yes, newly renumbered 410.16(C)(5) in the 2008 NEC (previously was 410.8) permits surface-mounted fluorescent or LED luminaires to be installed within the storage space where identified for this use. Section 410.16(C)(1), (C)(3) and (C)(5) permits LED luminaires in clothes closets within 12 inches for surface-mounted incandescent or LED luminaires with a completely enclosed light source installed on the wall above the door or on the ceiling; 6 inches for recessed incandescent or LED luminaires with a completely enclosed light source installed in the wall or the ceiling; and surface-mounted fluorescent or LED luminaires installed within the storage space where identified for this use.
FLACH, a regular contributing Code editor, is a former chief electrical inspector for New Orleans. He can be reached at 504.734.1720.