It’s no secret that many electrical professionals have a love/hate relationship with the National Electrical Code (NEC). The good news is it’s revised on a three-year cycle. The bad news is that three years pass all too quickly. Just when you think you’ve got a firm grip on the last set of revisions, a new comprehensive set of changes comes rolling at you. One would think that a document that’s been around since the late 1890s would only require minor tweaks and revisions. However, the steady introduction of new products and technologies into the marketplace — coupled with the release of new research findings by various public and private groups — creates a seemingly never-ending flow of necessary revisions (some of which are comprehensive) to this widely accepted electrical code.
In our continued efforts to serve your Code needs, we’ve enlisted the help of our trusty NEC Consultant Mike Holt to shed light on the key changes in this new edition of the Code. Once again, he’s delivered in a big way, covering everything from new GFCI and AFCI requirements to more grounding and bonding rules to conductor ampacity guidelines. All 25 changes highlighted in this article are supported by an analysis section, where Holt offers keen insight into why the change was brought about and how it might affect you on future projects. Although we’ve highlighted what we consider to be the most influential changes, it’s important to realize that this cycle produced a multitude of revisions.
So find a quiet place, dive into this article, and take all the time you need to absorb some of the most significant new articles, sections, exceptions, and fine print notes in the 2011 NEC. When you’re finished, you’ll undoubtedly feel one step ahead of the game.
A new section requires some equipment to be marked with the available fault current and requires updating of that marking if modifications of the electrical system occur.
110.24 Available Fault Current.
(A) Field Marking. Service equipment in other than dwelling units must be legibly field-marked with the maximum available fault current, including the date the fault current calculation was performed and be of sufficient durability to withstand the environment involved. (click here to see Fig. 1)
(B) Modifications. When modifications to the electrical installation affect the maximum available fault current at the service, the maximum available fault current must be recalculated to ensure the service equipment ratings are sufficient for the maximum available fault current at the line terminals of the equipment. The required field marking(s) in 110.24(A) must be adjusted to reflect the new level of maximum available fault current.
Exception: Field markings aren’t required for industrial installations where conditions of maintenance and supervision ensure that only qualified persons service the equipment.
Analysis: All equipment must have an interrupting rating or short circuit current rating that’s equal to or greater than the available fault current [110.9 and 110.10]. As premises wiring systems age, utilities may change transformers in an effort to become more efficient or to increase capacity. When this occurs, the available fault current increases, many times resulting in noncompliant (and dangerous) wiring systems. This NEC change is intended to alert Code users to the fact that when utilities change transformers — or when emergency or standby systems are installed — the ratings of equipment must be re-evaluated.
Opponents of this NEC change argue that oftentimes the ratings of equipment are based on a “worst-case” scenario. While this is suitable for designing a system, it isn’t suitable for performing the calculations required to establish the proper personal protective equipment (PPE) necessary to work on the equipment. When artificially high values of fault current are used for equipment ratings, a lower PPE rating is often the result of the calculations.
There were several changes made to this section of the Code, addressing accessibility and location issues.
A new requirement addresses the accessibility of the test and reset functions of GFCI devices.
210.8 GFCI Protection. Ground-fault circuit interruption for personnel must be provided as required in 210.8(A) through (C). The Ground-fault circuit-interrupter device must be installed at a readily accessible location.
Analysis: The Code previously didn’t address the accessibility of the test and reset functions of GFCI devices. This presents two problems: First, building owners are subjected to the inconvenience of using ladders (or less safe devices) to reach the reset button should a GFCI device trip. Secondly, the listing standards of GFCIs require that they be tested on a monthly basis. While it’s true that many people don’t test their GFCI devices, some who would perform such tests won’t go through the extra effort of finding a ladder to access these devices if they aren’t readily accessible.
This change will require GFCIs in obvious locations, such as bathrooms and dwelling unit garages, to have their test and reset buttons readily accessible, but it also applies to less obvious locations, such as receptacles on rooftops and in soffits for holiday lighting.
A revision to this next requirement increases the locations of GFCI-protected outlets in patient care areas of health care facilities.
210.8(B)(5) Sinks. All 15A and 20A, 125V receptacles installed within 6 ft of the outside edge of a sink must be GFCI-protected.
Ex. 1: In industrial laboratories, receptacles used to supply equipment where removal of power would introduce a greater hazard aren’t required to be GFCI-protected.
Ex. 2: Receptacles located in patient bed locations of general care or critical care areas of health care facilities aren’t required to be GFCI-protected.
Analysis: A change to the 2008 NEC required GFCI protection near all sinks in nondwelling occupancies. One of the concerns raised by this change was the need for life support equipment to be supplied by an outlet that isn’t GFCI-protected. Due to this, an exception was written that exempted all receptacles in patient care areas (other than bathrooms). Although this certainly took care of the life support issue, it also removed GFCI protection from all other equipment that isn’t life safety oriented. For example, the many sinks found in a dental office were exempt, despite the fact that the patient is often very vulnerable to electric shock due to the invasive nature of many dental procedures. This change more accurately expresses the concerns of the medical community, while adding protection to equipment that isn’t essential to life support.
GFCI protection was added to indoor wet locations of nondwelling occupancies.
210.8(B)(6) Indoor wet locations. All 15A and 20A, 125V receptacles installed indoors in wet locations must be GFCI-protected.
Analysis: Many areas, such as car washes, food processing areas, and similar locations, share the same hazards as outdoor locations, yet GFCI protection has never been required in these locations. This change will now require that these areas receive the same protection against electric shock as required for outdoor locations. It’s worth noting that this change was accepted without any documented incidents cited.
A new requirement for GFCI protection of 15A and 20A, 125V receptacles near showering facilities was added.
210.8(B)(7) Locker Rooms. All 15A and 20A, 125V receptacles installed in locker rooms with associated showering facilities must be GFCI-protected.
Analysis: Requirements for GFCI protection of receptacles in bathrooms have been in place for a very long time. In Art. 100, a bathroom is very clearly defined — and not all locker rooms fall under that definition. The hazards that exist in a bathroom are the same as those encountered in a locker room — and perhaps even more so. A typical locker room that has associated showering facilities will probably contain tiled floors that are wet, people with bare feet, and people using electrical appliances (razors, hair dryers, curling irons, etc.). Therefore, GFCI protection was added for all 15A and 20A, 125V receptacles located in these facilities.
A new requirement adds GFCI protection for receptacles located in nondwelling unit garages that don’t fall under the scope of Article 511.
210.8(B)(8) Garages. All 15A and 20A, 125V receptacles installed in garages, service bays, and similar areas where electrical diagnostic equipment, electrical hand tools, or portable lighting equipment are to be used must be GFCI-protected. (click here to see Fig. 2)
Analysis: This change expands GFCI protection requirements to all commercial garages. Article 511 applies only to those garages “in which volatile flammable liquids or flammable gases are used for fuel or power.” A facility that repairs only diesel-powered vehicles doesn’t fall under the requirements of Article 511, because diesel fuel is a combustible liquid, not a flammable liquid. Although the same electric shock hazards exist regardless of the fuel type employed, areas that use only diesel fuel didn’t require GFCI protection in previous editions of the Code.
Changes have been made to this section to address fire alarm circuiting, Type MC Cables, concrete-encased raceways, and branch circuit extensions or modifications.
210.12(A) Where Required. All 15A or 20A, 120V branch circuits in dwelling units supplying outlets in family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similar rooms or areas must be protected by a listed AFCI device of the combination type. (click here to see Fig. 3)
Ex. 1: AFCI protection can be of the branch circuit type located at the first outlet if the circuit conductors are installed in RMC, IMC, EMT, or Type MC or steel armored Type AC cable meeting the requirements of 250.118, and the AFCI device is contained in a metal outlet or junction box.
Ex. 2: Where a listed metal or nonmetallic conduit or tubing is encased in not less than 2 in. of concrete for the portion of the branch circuit between the branch circuit overcurrent device and the first outlet, an outlet branch circuit AFCI at the first outlet is permitted to provide protection for the remaining portion of the branch circuit.
Ex. 3: AFCI protection can be omitted for an individual branch circuit to a fire alarm system in accordance with 760.41(B) and 760.121(B), if the circuit conductors are installed in RMC, IMC, EMT, or steel sheath Type AC or MC cable that qualifies as an equipment grounding conductor in accordance with 250.118, with metal outlet and junction boxes.
(B) Branch-Circuit Extensions or Modifications — Dwelling Units. Where branch-circuit wiring is modified, replaced, or extended in any of the areas specified in 210.12(A), the branch circuit must be protected by:
(1) A listed combination AFCI located at the origin of the branch circuit; or
(2) A listed outlet branch circuit AFCI located at the first receptacle outlet of the existing branch circuit.
Analysis: Fire alarm systems covered by Art. 760 have been exempted from the requirements of AFCI protection, but the circuiting of those systems was previously not addressed. This inadvertently left a loophole for installers to incorporate other outlets in areas specified by 210.12 on the same circuit as the fire alarm system and omit the AFCI protection required for circuits in those areas. This change also includes MC cable as a permitted wiring method when employing this exception.
Section 210.12 Ex. 1 has been revised to allow MC cables as one of the allowable wiring methods in the exception. MC cable meeting the requirements of 250.118 has been proven safe, so this allowance seems fair enough.
New to the NEC is 210.12(A) Ex. 2. Concrete encased raceways obviously provide an increased level of protection for circuit conductors, so a new exception was added to allow such raceways to be installed without AFCI protection at the source, provided that there’s an outlet type AFCI installed at the first outlet of the circuit.
Also new to the NEC is subsection (B), dealing with branch-circuit extensions or modifications in existing buildings. The question of what to do with existing buildings in regard to AFCI protection has been prevalent ever since AFCI requirements were added to the Code in 1999. With this change, it’s clear that when branch circuit wiring is extended or modified, some level of AFCI protection will be required.
A change to the wall spacing requirements has been made to address fixed cabinets, and the wall spacing requirements have been clarified.
210.52(A)(2) Definition of Wall Space.
(1) Any space 2 ft or more in width, unbroken along the floor line by doorways and similar openings, fireplaces, and fixed cabinets.
(2) The space occupied by fixed panels in exterior walls.
(3) The space occupied by fixed room dividers, such as freestanding bar-type counters or guard rails.
(3) Floor Receptacle Outlets. Floor receptacle outlets aren’t counted as the required receptacle wall outlet if they’re located more than 18 in. from the wall.
(4) Countertop Receptacles. Receptacles installed for countertop surfaces as required by 210.52(C) can’t be used to meet the receptacle requirements for wall space as required by 210.52(A). (click here to see Fig. 4)
Analysis: The substantiation for the change to (A)(2)(1) is to deal with kitchen cabinets. Obviously, the Code doesn’t expect a receptacle installed in front of lower kitchen cabinets to satisfy the wall space receptacles of this section. While this makes sense — and seems to be a clarification that’s worth making — it also brings with it technical changes as well. For example, built-in bookcases often consume entire walls in dwelling unit libraries, studies, offices, and similar rooms. With this change, it seems receptacles are no longer required in such bookcases.
Changes made to 210.52(A)(4) have been done to address a fairly odd situation. It’s quite common for a kitchen peninsular or island countertop to create a “wall” between the kitchen and dining room (or other room). When this occurs, 210.52(A)(1) requires receptacles on the back of the peninsula or island in order to accommodate the dining area. In previous NEC editions, the required countertop receptacle could be used to satisfy this requirement, provided the receptacle wasn’t higher than 5½ ft above the floor [210.52(4)]. This not only made for a Code-compliant installation, but also an invitation to have cords stretched across the dining room in order to reach the elevated receptacle. This change eliminates that loophole from the NEC and clearly states that the required countertop receptacles required by 210.52(C) are in addition to any receptacles required in other parts of 210.52(A).
A 15A or 20A, 125V receptacle is now required in dwelling unit accessory buildings.
210.52(G) Dwelling Unit Garage, Basement, and Accessory Building Receptacles.
(1) Not less than one 15A or 20A, 125V receptacle outlet, in addition to any provided for a specific piece of equipment, must be installed in each basement, in each attached garage, and each detached garage or accessory building with electric power.
Analysis: The NEC has long required a 15A or 20A, 125V receptacle for detached dwelling unit garages that are provided with electric power. This Code change recognizes the fact that many accessory buildings to dwellings aren’t garages, but rather workshops, storage sheds, and similar buildings. Storage sheds are often used to house lawn and garden equipment, some of which require electricity for battery charging and other purposes. The NEC now requires a receptacle to be installed in these buildings whenever there’s electric power installed in them (for lighting or similar purposes).
A new requirement to provide receptacles in foyers was added.
210.52(I) Foyer Receptacles. Foyers that aren’t part of a hallway [210.52(H)] having an area greater than 60 sq ft must have a receptacle located on any wall space 3 ft or more in width and unbroken by doorways, floor to ceiling windows, and similar openings.
Analysis: Newer homes are often built with substantial foyers, some of which can be larger than other rooms of the house. In previous editions of the Code, these areas were typically treated as hallways, with only one receptacle being required and only one being installed. This change will now require foyers to have the same receptacle requirements as a bedroom, family room, dining room, or similar area. I guess the only question now is…what’s a foyer?
A new term “supply-side bonding jumper” was added.
250.2 Definitions.
Bonding Jumper, Supply-Side. A conductor on the supply side or within a service or separately derived system to ensure the electrical conductivity between metal parts required to be electrically connected. (click here to see Fig. 5)
Analysis: Equipment bonding jumpers are used often in the NEC, although the manner in which they’re sized depends on the location (in the circuit) of the bonding jumper. Generally speaking, bonding conductors located downstream of an overcurrent device are sized in accordance with 250.122, based on the rating of the overcurrent device. Bonding conductors upstream of an overcurrent device, such as the supply side of a service or between a transformer and panelboard, are typically sized using Table 250.66 and the 12½% rule discussed in 250.102(C). This Code change not only provides a new term to more accurately describe an existing conductor, but also should help clear up the sizing confusion that many people have with bonding conductors.
This section has been reorganized and includes many revisions and notes to clarify the grounding and bonding requirements of separately derived systems.
(A) Grounded Systems. Separately derived systems must be grounded and bonded in accordance with (A)(1) through (A)(8).
(3) System Neutral Conductor Size. If the system bonding jumper is installed at the disconnecting means instead of at the source, the following requirements apply:
(a) Sizing for Single Raceway. Because the neutral conductor of a derived system serves as the effective ground-fault current path for ground-fault current, it must be routed with the ungrounded conductors of the derived system and be sized not smaller than specified in Table 250.66, based on the area of the ungrounded conductor of the derived system. (click here to see Fig. 6)
(b) Parallel Conductors in Two or More Raceways. If the conductors from the derived system are installed in parallel in two or more raceways, the neutral conductor of the derived system in each raceway or cable must be sized not smaller than specified in Table 250.66, based on the area of the largest ungrounded conductor of the derived system in the raceway or cable. In no case is the neutral conductor of the derived system permitted to be smaller than 1/0 AWG [310.10(H)].
(6) Grounding Electrode Conductor, Multiple Separately Derived Systems.
(a) Common Grounding Electrode Conductor. The common grounding electrode conductor can be one of the following:
(1) A conductor not smaller than 3/0 AWG copper or 250kcmil aluminum.
(2) The metal frame of the building/structure that complies with 250.52(A)(2) or is connected to the grounding electrode system by a conductor not smaller than 3/0 AWG copper or 250kcmil aluminum.
(C) Outdoor Source. If the separately derived system is located outside the building/structure, a connection to the grounding electrode must be made at the separately derived system location.
Analysis: Considering the amount of changes that have occurred in this section, it wouldn’t be entirely inaccurate to say that the whole section has been rewritten. Here are a couple of items worth noting.
Section 250.30(A)(3) mainly borrows the text that was previously in 250.30(A)(8). It does, however, add new text to provide guidance on sizing the grounded conductor for a delta (corner grounded) system. In these applications, the grounded conductor must be the same size as the ungrounded conductors.
In 250.30(A)(6), the grounding electrode conductor(s) for multiple separately derived systems has been changed to clarify that structural metal can be used to ground multiple separately derived systems, provided that the structural metal complies with 250.52(A)(2) or is connected to the grounding electrode system by a conductor not smaller than 3/0 AWG CU or 250kcmil AL.
Section 250.30(C) is new to the NEC. This subsection addresses separately derived systems that are installed outside of a building or other structure. When this is the case, a grounding electrode connection to the transformer must be provided.
The rule explaining when a structural metal frame can serve as a grounding electrode has been changed again, and the requirements for concrete encased electrodes, ground rods, and ground plates have been clarified.
250.52 Grounding Electrode Types.
(A) Electrodes Permitted for Grounding.
(1) Underground Metal Water Pipe Electrode. Underground metal water pipe in direct contact with the earth for 10 ft or more can serve as a grounding electrode.
(2) Metal Frame Electrode. The metal frame of a building/structure can serve as a grounding electrode when it meets at least one of the following conditions:
(1) At least one structural metal member is in direct contact with the earth for 10 ft or more, with or without concrete encasement.
(2) The bolts securing the structural steel column are connected to a concrete encased electrode [250.52(A)(3)] by welding, exothermic welding, steel tie wires, or other approved means. (click here to see Fig. 7)
(3) Concrete-Encased Electrode. At least 20 ft of either (1) or (2):
(1) One or more of bare, zinc-galvanized, or otherwise electrically conductive steel reinforcing bars of not less than ½ in. diameter, mechanically connected together by steel tie wires, welding, or other effective means, to create a 20 ft or greater length.
(2) Bare copper conductor not smaller than 4 AWG.
The reinforcing bars or bare copper conductor must be encased by at least 2 in. of concrete located horizontally near the bottom of a concrete footing or vertically within a concrete foundation that’s in direct contact with the earth.
If multiple concrete-encased electrodes are present at a building/structure, only one is required to serve as a grounding electrode
Note: Concrete containing insulation, vapor barriers, films or similar items separating it from the earth isn’t considered to be in “direct contact” with the earth.
(4) Ground Ring Electrode. A ground ring consisting of at least 20 ft of bare copper conductor not smaller than 2 AWG buried in the earth encircling a building/structure can serve as a grounding electrode.
(5) Ground Rod and Pipe Electrode. Ground rod electrodes must not be less than 8 ft in length in contact with the earth [250.53(G)].
(b) Rod-type electrodes must have a diameter of at least 5⁄8 in., unless listed.
(6) Listed Electrode. Other listed grounding electrodes.
(7) Ground Plate Electrode. A bare or conductively coated iron or steel plate with not less than ¼ in. of thickness, or a solid uncoated copper metal plate not less than 0.06 in. of thickness, with an exposed surface area of not less than 2 sq ft.
(8) Metal Underground Systems Electrode. Metal underground piping systems, underground tanks, and underground metal well casings can serve as a grounding electrode.
Analysis: Over the last few Code cycles, the NEC has tried to make clear when the structural metal of a building or structure can be used as a grounding electrode. The first prescribed method will find the structural metal with direct earth contact for 10 ft or more. As an alternative, the hold-down bolts securing the structural metal column can be connected to a concrete-encased electrode. Previously, the Code allowed the structural metal to serve as an electrode if it was connected to a ground rod meeting the 25-ohm requirement of (formerly) 250.56. This option has now been removed and is no longer a suitable method of bonding the structural metal to qualify it as a grounding electrode.
The ways of creating a concrete-encased electrode have been changed into an easy-to-use list format, and a clarification has been made regarding the use of vapor barriers.
When a vapor barrier (typically a plastic sheet) is installed beneath the footing, NEC users have debated whether or not the concrete is still considered to be in direct contact with earth. A new Informational Note was added to clarify that such a footing isn’t considered to be in direct contact with the earth; therefore, the rebar or bare copper conductor can’t be used as a grounding electrode.
Section 250.52(A)(5) has been changed to eliminate the minimum size for listed electrodes. Previous editions of the Code have stated that listed ground rods must be at least ½ in. in diameter. Because the NEC is typically not the place to find listing requirements, this text has been removed, which might open the door to smaller ground rods being listed.
Lastly, a change was made to 250.52(A)(7), which clarifies that plate electrodes must be conductive(!).
The 25-ohm rule has been relocated and greatly clarified. Editorial changes to this section have also been made, and the Informational Note has been revised.
250.53 Grounding Electrode Installation Requirements.
(A) Rod, Pipe, or Plate Electrodes.
(1) Below Permanent Moisture Level. If practicable, rod, pipe, and plate electrodes must be embedded below the permanent moisture level and be free from nonconductive coatings such as paint or enamel.
(2) Supplemental Electrode. A single rod, pipe, or plate electrode must be supplemented by an additional electrode that’s bonded to one of the following:
(1) The single rod, pipe, or plate electrode
(2) The grounding electrode conductor of the single electrode
(3) The neutral service-entrance conductor
(4) The nonflexible grounded service raceway
(5) The service enclosure
Ex.: If a single rod, pipe, or plate grounding electrode has an earth contact resistance of 25 ohms or less, the supplemental electrode isn’t required.
(3) Spacing. The supplemental electrode for a single rod, pipe, or plate electrode must be installed not less than 6 ft from the single electrode. (click here to see Fig. 8)
Note: The efficiency of paralleling electrodes is improved by spacing them at least twice the length of the longest rod.
Analysis: The long-standing rule that a ground rod as well as a pipe or plate electrode must have a resistance to earth of
25 ohms or less or be supplemented by an additional electrode was well understood until recent revisions to the NEC created confusion. These revisions left the Code user trying to figure out if a concrete-encased electrode required a supplement and when a ground rod is actually required. Revisions to this section now match the standard industry practice of (when required) driving two ground rods instead of testing the resistance of a single driven rod. The 25-ohm language is now written as an exception, recognizing this practice. Code users will notice that 250.56 has been deleted as a result of this change, but the technical provisions contained therein haven’t disappeared.
The Informational Note explaining the logic of spacing ground rods more than 6 ft apart, while technically true, didn’t provide any guidance as to what the spacing should be. This change clarifies that the driven rods should be at least twice the length of the longer of the two rods. For example, two rods 8 ft in length should be driven at least 16 ft apart. It’s worth remembering that this is an Informational Note, not a Code requirement [90.5(C)].
A new section was added to prohibit the use of the equipment grounding conductor as a grounding electrode conductor.
250.121 Use of Equipment Grounding Conductors. An equipment grounding conductor isn’t permitted to be used as a grounding electrode conductor.
Analysis: The grounding electrode conductor (GEC) is intended to help direct lightning-induced energy to the earth, while an equipment grounding conductor (EGC) is intended to provide a low-impedance ground-fault current path to the source to operate overcurrent devices in the event of a ground fault. The requirements for sizing are also different. An EGC is sized in accordance with 250.122, while a GEC is sized using 250.66. Because these conductors have different rules, different sizing requirements, and different installation requirements, this section was added to clarify that one conductor can’t fill the roles of both an EGC and a GEC.
This rule has been revised to be more technically accurate.
300.4 Protection Against Physical Damage. Conductors, raceways, and cables must be protected against physical damage [110.27(B)].
Analysis: Previous editions of the NEC have required protection of conductors where subject to physical damage. While most Code users understand this rule is intended to apply to all conductors in all wiring methods, it didn’t clearly state that. This revision makes it clear that all conductors in all wiring methods must be protected from physical damage.
The rule on protecting raceways under metal-corrugated sheet roof decking has been expanded.
300.4(E) Wiring Under Roof Decking. Cables, raceways, and enclosures under metal-corrugated sheet roof decking must not be located within 1½ in. of the roof decking, measured from the lowest surface of the roof decking to the top of the cable, raceway, or box. In addition, cables, raceways, and enclosures aren’t permitted in concealed locations of metal-corrugated sheet decking type roofing.
Ex: Spacing from roof decking doesn’t apply to rigid metal conduit and intermediate metal conduit.
Analysis: New to the 2008 NEC was a requirement for the protection of most raceways when installed within 1½ in. of the roof deck. Although this 2008 rule change went a long way toward protecting wiring systems from damaging roofing screws that can penetrate the raceways, it left out one critical part of the installation — boxes. With this change, it’s clear that the Code is concerned not only with protecting the raceways, but also the boxes.
This rule was also changed to prohibit wiring methods from being installed in concealed locations above the roof decking. In some instances, installers place raceways above the roof deck prior to the insulation being installed, which results in the same potential for damage from roofing screws.
The requirement for protection of conductors 4 AWG and larger has been changed to add clarity.
300.4(G) Insulating Fittings. If raceways contain insulated circuit conductors 4 AWG and larger that enter an enclosure, the conductors must be protected from abrasion during and after installation by a fitting identified to provide a smooth, rounded insulating surface, such as an insulating bushing. (click here to see Fig. 9)
Ex.: Insulating bushings aren’t required if a raceway terminates in a threaded raceway entry that provides a smooth, rounded, or flared surface for the conductors. An example would be a meter hub fitting or a Meyer’s hub-type fitting.
Analysis: The term “substantial fitting” has been replaced with the term “identified” so that inspectors won’t have to interpret the Code unnecessarily. The term “identified” is clearly defined in Art. 100, is used throughout the NEC, and takes interpretation out of the requirement. Although fittings that are designed to provide this protection are typically used to achieve compliance with this requirement, it could have been argued that fittings designed for another application could satisfy this rule. This change removes that argument by making the NEC a more prescriptive document.
A new protection requirement for structural (expansion) joints was added.
300.4(H) Structural Joints. A listed expansion/deflection fitting or other approved means must be used where a raceway crosses a structural joint intended for expansion, contraction or deflection.
Analysis: In larger commercial/industrial buildings, it isn’t uncommon to see an expansion joint inside of the building. When these are encountered, the Code has never offered any guidance to the installer as it pertains to wiring methods. With this change, it becomes clear that a fitting or other approved means must be used to allow for expansion or deflection of the wiring method.
Type MI and Type MC Cables are now allowed to be installed under buildings without a raceway.
300.5(C) Cables Under Buildings. Cables installed under a building must be installed in a raceway that extends past the outside walls of the building.
Ex. 2: Type MC Cable listed for direct burial is permitted under a building without installation in a raceway [330.10(A)(5)]. (click here to see Fig. 10)
Analysis: Although certain types of MC cable are listed for direct burial and concrete encasement, this rule has prohibited them from being installed underneath buildings. This change now allows cables to be installed under the floor slab of a building, which has been accepted by many inspectors for some time. Interestingly, other cables that are listed for this application, such as UF cable, aren’t recognized by this change.
This change clarifies the use of single conductor cables installed in parallel.
300.5(I) Conductors Grouped Together. All conductors of the same circuit, including the equipment grounding conductor, must be inside the same raceway or in close proximity to each other. See 300.3(B).
Ex. 1: Conductors can be installed in parallel in raceways, multiconductor cables, or direct-buried single-conductor cables. Each raceway or multiconductor cable must contain all conductors of the same circuit, including the equipment grounding conductor. Each direct-buried single-conductor cable must be located in close proximity in the trench to the other single-conductor cables in the same parallel set of conductors, including equipment grounding conductors.
Ex. 2: Parallel circuit conductors installed in accordance with 310.10(H) of the same phase or neutral can be installed in underground PVC conduits, if inductive heating at raceway terminations is reduced by the use of aluminum locknuts and cutting a slot between the individual holes through which the conductors pass as required by 300.20(B).
Analysis: Conductors of the same circuit are required to be grouped in the same raceway or cable to help reduce the inductive reactance of the conductors. A very literal reading of previous Code editions didn’t address the use of single-conductor cables, such as many USE cables, in parallel installations. The NEC now recognizes this practice while giving guidance on how to install these cables. The issues of inductive reactance are addressed by requiring these single-conductor cables to be installed within close proximity of each other.
The rule requiring identification of electrical ceiling support wires has been expanded.
300.11(A)(2) Nonfire-Rated Ceiling Assembly. Wiring in a nonfire-rated floor-ceiling or roof-ceiling assembly can be supported by independent support wires attached to the ceiling assembly. The independent support wires must be distinguishable from the suspended-ceiling support wires by color, tagging, or other effective means. (click here to see Fig. 11)
Analysis: Identification of ceiling-support wires that are used for electrical equipment was previously limited to those wires that are in fire-resistance-rated ceiling assemblies. In order to distinguish which wires are installed by the electrician and which are installed by the ceiling contractor, this change requires identification of the independent support wires for all ceiling systems, whether the ceiling assembly is fire-resistance rated or not.
Extensive revisions have been made to the language of this section, and a new subsection was added addressing cable trays.
300.22 Wiring in Ducts Not for Air Handling, Fabricated Ducts for Environmental Air, and Other Spaces For Environmental Air (Plenums). The provisions of this section apply to the installation and uses of electrical wiring and equipment in ducts used for dust, loose stock, or vapor removal; ducts specifically fabricated for environmental air, and spaces used for environmental air (plenums).
(A) Ducts Used for Dust, Loose Stock, or Vapor. Ducts that transport dust, loose stock, or vapors must not have any wiring method installed within them.
(B) Ducts Specifically Fabricated for Environmental Air. If necessary for direct action upon, or sensing of, the contained air, Type MC cable that has a smooth or corrugated impervious metal sheath without an overall nonmetallic covering, electrical metallic tubing, flexible metallic tubing, intermediate metal conduit, or rigid metal conduit without an overall nonmetallic covering can be installed in ducts specifically fabricated to transport environmental air. Flexible metal conduit in lengths not exceeding 4 ft can be used to connect physically adjustable equipment and devices within the fabricated duct.
Equipment is only permitted within the duct specifically fabricated to transport environmental air if necessary for the direct action upon, or sensing of, the contained air. Equipment, devices, and/or illumination are only permitted to be installed in the duct if necessary to facilitate maintenance and repair.
(C) Other Spaces Used for Environmental Air (Plenums). This section applies to wiring and equipment in spaces not specifically fabricated for environmental air-handling purposes (plenums) but used for air-handling purposes as a plenum. This requirement doesn’t apply to habitable rooms or areas of buildings, the prime purpose of which isn’t air handling.
Note 1: The spaces above a suspended ceiling or below a raised floor used for environmental air are examples of the type of space to which this section applies. (click here to see Fig. 12)
Note 2: The phrase “other space used for environmental air (plenum)” correlates with the term “plenum” in NFPA 90A, Standard for the Installation of Air-Conditioning and Ventilating Systems, and other mechanical codes where the plenum is used for return air purposes, as well as some other air-handling spaces.
(1) Wiring Methods. Electrical metallic tubing, rigid metal conduit, intermediate metal conduit, armored cable, metal-clad cable without a nonmetallic cover, and flexible metal conduit can be installed in environmental air spaces. If accessible, surface metal raceways or metal wireways with metal covers can be installed in environmental air spaces.
(2) Cable Tray Systems.
(a) Metal Cable Tray Systems. Metal cable tray systems can be installed to support the wiring methods and equipment permitted by this section. (click here to see Fig. 13)
(3) Equipment. Electrical equipment with a metal enclosure or nonmetallic enclosures listed for use within an air-handling space (plenum) and having adequate fire-resistant and low-smoke-producing characteristics can be installed.
Analysis: There’s long been confusion about the terms “plenum” and “other space(s) used for environmental air.” While nearly all mechanical codes (NFPA 90A, Standard for the Installation of Air-Conditioning and Ventilating Systems, International Mechanical Code (IMC), and Uniform Mechanical Code (UMC)) use the term “plenum” for anything that moves environmental air, the NEC only referred to a physically constructed duct as a “plenum.” The space beneath a raised floor and the space above a suspended ceiling (when used for air handling) were referred to as “other spaces used for environmental air.” Obviously, the Code shouldn’t be the document that defines air system components, yet manufacturers were forced to have their product literature include provision for these “other spaces,” which created massive confusion for people installing, designing, and inspecting mechanical systems. The confusion was rampant enough to require an Informational Note in the NEC trying to explain what these spaces really were. With the change, a component of an air-handling system that’s created for the sole purpose of moving air (such as a duct made of tin or drywall) is now called a “duct specifically fabricated for environmental air.” The space above a ceiling or below a floor that’s used for air moving isn’t fabricated for that sole purpose; therefore, it isn’t a “duct,” according to mechanical codes. These spaces are now referred to as “other spaces used for environmental air (plenums),” which correlates with other codes and also has the desired effect of using commonly accepted trade language — most people refer to the space above a suspended ceiling as a “plenum ceiling,” not an “other space used for environmental air ceiling.”
Additional changes to this section include a new provision dealing with cable trays in other spaces used for environmental air (plenums), which requires these cable trays to be metallic.
Solid metal cable trays with metal covers can be used to support and enclose wiring methods that traditionally weren’t allowed in these locations.
This section, dealing with the ampacity of conductors, has been extensively revised.
310.15(B) Ampacity Table. The allowable conductor ampacities listed in Table 310.15(B)(16) are based on conditions where the ambient temperature isn’t more than 86°F, and no more than three current-carrying conductors are bundled together.
The temperature correction and adjustment factors apply to the ampacity for the temperature rating of the conductor, provided the corrected and adjusted ampacity doesn’t exceed the ampacity for the temperature rating of the termination in accordance with the provisions of 110.14(C).
(2) Ambient Temperature Correction Factors. When conductors are installed in an ambient temperature other than 78°F to 86°F, the ampacities listed in Table 310.15(B)(16) must be corrected in accordance with the multipliers listed in Table 310.15(B)(2)(a). (click here to see Fig. 14)
(4) Ampacity adjustment factors don’t apply to conductors within Type AC or Type MC cable under the following conditions:
(a) The cables don’t have an outer jacket,
(b) Each cable has no more than three current-carrying conductors,
(c) The conductors are 12 AWG copper, and
(d) No more than 20 current-carrying conductors (ten 2-wire cables or six 3-wire cables) are installed without maintaining spacing for a continuous length longer than 24 in.
(5) Ampacity adjustment of 60% applies to conductors within Type AC or Type MC cable without an overall outer jacket under the following conditions:
(b) The number of current-carrying conductors exceeds 20.
(c) The cables are stacked or bundled longer that measure 24 in. without spacing being maintained.
Analysis: In this edition of the Code, the term “derate(ing)” isn’t used at all, except in a few instances. The term “ampacity adjustment” is used throughout the NEC when referring to conductors that are bundled or used on rooftops, and the term “correction” is used when conductors are subjected to temperatures other than 86°F.
Conductors with insulation temperature ratings higher than the termination’s temperature rating can be used for conductor ampacity adjustment, correction, or both [110.14(C)]. This means conductor ampacity must be based on the conductor’s insulation temperature rating listed in Table 310.15(B)(16), as adjusted for ambient temperature correction factors, conductor bundling adjustment factors, or both. This change clarifies that, after applying these adjustments and corrections, the resulting ampacity still can’t exceed the temperature limitations of the equipment termination.
The temperature correction factors formerly found at the bottom of (then) Table 310.16 in the 2008 NEC, were some of the least user-friendly in the Code. This new table provides a remarkably easier format, with less confusion and proper application being the end result. An interesting addition to this table is borrowed from the Canadian Electrical Code — the allowance of smaller conductors when installed in an ambient temperature of less than 70°F. With this allowance, the NEC user can use up to 115% of the conductor’s ampacity in certain conditions, which can result in a smaller conductor. While previous editions of the Code recognized colder environments, it allowed only for an increase to 104% of the conductor’s ampacity — a value that never really made the math worthwhile.
Previous editions of the NEC used the term “nipple” to describe a raceway that’s 24 in. or less in length. This resulted in Code users debating about the physical characteristics of the raceways, such as whether or not the raceway could contain bends. This change takes away that argument by removing the term “nipple(s)” and replacing it with “raceway(s).” One no longer needs to guess at the intent of this section and now needs only to measure the length and determine the appropriate rules.
The term “bundled” has been used for several Code cycles to describe when ampacity adjustment is required. Because the term isn’t defined in Art. 100, many people struggle in their attempts to determine when to apply the adjustment provisions of this section. While the phrase “installed without maintaining spacing” is also not defined, some NEC users may find it an easier phrase to understand and apply. This change isn’t intended to be a technical one, but rather an editorial one.
New to the 2008 Code came a rule requiring that all conductors installed in conduits on rooftops have their ampacities adjusted dramatically. The term “conduit,” while not defined in the NEC, doesn’t include raceways such as EMT, ENT, and FMT. With this change, conductors installed in these raceways will now have to have their ampacities adjusted as well.
The ampacity of some conductors in Table 310.15(B)(16) (formerly 310.16) didn’t match those found in the Canadian Electrical Code and were therefore changed. While no technical evidence was submitted showing insulation failure of the conductors, this proposal was passed. The end result was a change to the ampacities of:
Copper conductors: 14, 12, 3, and 1 AWG, and 600kcmil, 1,500kcmil and 2,000kcmil.
Aluminum conductors: 12, 8, and 6 AWG, and 300kcmil, 700kcmil, and 800kcmil.
New provisions for power distribution blocks in pull and junction boxes have been added.
314.28 Boxes and Conduit Bodies for Conductors 4 AWG and Larger.
(E) Power Distribution Block. Power distribution blocks installed in junction boxes over 100 cu in. must comply with the following (click here to see Fig. 15):
(1) Installation. Be listed as a power distribution block.
(2) Size. Be installed in a box not smaller than required by the installation instructions of the power distribution block.
(3) Wire-Bending Space. The junction box is sized so that the wire-bending space requirements of 312.6 can be met.
(4) Live Parts. Exposed live parts on the power distribution block aren’t present when the junction box cover is removed.
(5) Through Conductors. Where the junction box has conductors that don’t terminate on the power distribution block(s), the through conductors must be arranged so the power distribution block terminals are unobstructed following installation.
Analysis: Power distribution blocks have a history of being used in large pull and junction boxes despite the fact that the Code has been silent on these installations. The only requirements for power distribution blocks were found in Art. 376, which applies only to metal wireways. This left uncertainty regarding the installation requirements for these blocks in boxes. The NEC now addresses this practice and provides clear, concise rules.
Only boxes exceeding 100 cu. in. can contain these blocks, and they must be listed. The values in Table 312.6 can be used for bending space at the terminals, and live parts must be covered just as required for wireways.
A new rule will require a neutral conductor at nearly every switch point.
404.2 Switch Connections.
(C) Switches Controlling Lighting. Switches controlling line-to-neutral lighting loads must have a neutral provided at the switch location.
Ex.: The neutral conductor isn’t required at the switch location if:
(1) The conductors for switches enter the device box through a raceway that has sufficient cross-sectional area to accommodate a neutral conductor. (click here to see Fig. 16)
(2) Cable assemblies for switches enter the box through a framing cavity that’s open at the top or bottom on the same floor level or through a wall, floor, or ceiling that’s unfinished on one side.
Note: The purpose of the neutral conductor is to complete a circuit path for electronic lighting control devices.
Analysis: Many lighting control devices (such as occupancy sensors) require that the switch be provided with standby voltage and current at the switch in order to operate. Many electricians don’t include a neutral conductor at switch locations, and the unfortunate result is the equipment grounding conductor being used as the neutral conductor. While the current on the equipment grounding conductor is typically less than 0.50mA, the accumulation of many switches in a building can result in an unacceptable amount of current on the equipment grounding conductors. With this change, gone are the days of using dead-end 3-way switches and two conductor switch loops.
The two exceptions address switch locations that use raceways and those that are at or near unfinished/accessible areas. The use of a raceway obviously allows the installer to pull in a neutral conductor should the need arise (provided the raceway is of adequate size), and the other exception allows for changing the wiring of the switch without resorting to removing drywall and other finish materials.
An Informational Note emphasizes the fact that this provision is for adding a dimmer switch. It’s a bit surprising to see this Informational Note, due to the fact that statements of intent are typically not allowed in the Code.
A new requirement addresses the replacement of receptacles in areas requiring AFCI protection, tamper-resistant receptacles, or weather-resistant receptacles.
406.4 General Installation Requirements.
(D) Receptacle Replacement.
(4) Arc-Fault Circuit Interrupters. Effective Jan. 1, 2014, where a receptacle outlet is supplied by a branch circuit that requires arc-fault circuit-interrupter protection [210.12(A)], a replacement receptacle at this outlet must be one of the following.
(1) A listed (receptacle) outlet branch-circuit type arc-fault circuit-interrupter receptacle.
(2) A receptacle protected by a listed (receptacle) outlet branch-circuit type arc-fault circuit-interrupter type receptacle.
(3) A receptacle protected by a listed combination type arc-fault circuit interrupter type circuit breaker.
(5) Tamper-Resistant Receptacles. Listed tamper-resistant receptacles must be provided where replacements are made at receptacle outlets that are required to be tamper-resistant elsewhere in this Code.
(6) Weather-Resistant Receptacles. Weather-resistant receptacles must be provided where replacements are made at receptacle outlets that are required to be so protected elsewhere in the Code.
Analysis: As aging wiring systems become more of a concern in the electrical industry, the Code is taking a proactive approach to providing protection of these systems. Many areas of a dwelling require the use of AFCI protection in an effort to help avoid electrical fires. When AFCIs were first introduced into the NEC, the substantiation for their inclusion was based largely on electrical fires in older homes. With the inception of these devices, the Code began protecting new and future wiring systems but didn’t address the older ones that contained many of the fires discussed in the AFCI arguments. This change expands the AFCI requirements to older homes. Because these older homes often don’t contain an equipment grounding conductor, installation of an AFCI circuit breaker does very little in the way of protecting the branch circuits. The receptacle-type AFCIs also provide a significantly lower level of protection, but they will be required, nonetheless.
This requirement has an effective date of Jan. 1, 2014.
The 2008 NEC introduced the concept of tamper-resistant receptacles in dwelling units. The requirements of that section (406.11, now 406.12) apply to new installations. It could have been argued that one could install tamper-resistant receptacles in the locations required by 406.11, then remove them and replace them with traditional receptacles. While most people will agree that this argument is a huge stretch of the imagination, this change eliminates the issue before it arises. It also requires that, on existing dwelling units, any receptacles that are replaced will need to be replaced using tamper-resistant receptacles.
A similar change was made for weather-resistant receptacles, using the same logic as tamper-resistant receptacles.
The required locations for tamper-resistant receptacles in dwellings have been lessened, and a clarification has been made.
406.12 Tamper-Resistant Receptacles in Dwelling Units. All nonlocking type 15A and 20A, 125V receptacles in the following areas of a dwelling unit [210.52] must be listed as tamper-resistant.
Ex.: Receptacles in the following locations aren’t required to be tamper-resistant:
(1) Receptacles located more than 5½ ft above the floor.
(2) Receptacles that are part of a luminaire or appliance.
(3) A receptacle located within dedicated space for an appliance that in normal use isn’t easily moved from one place to another.
(4) Nongrounding receptacles used for replacements as permitted in 406.4(D)(2)(a).
Analysis: Receptacles installed above 5½ ft obviously don’t pose the same risk to small children as those below that elevation. Likewise, receptacles that are rendered inaccessible by equipment, and those that are part of luminaires don’t pose the same risk. The Code has recognized these facts and included an exception for them in this edition of the NEC.
An allowance has also been made to address the replacement of nongrounding receptacles because currently there are no nongrounding tamper-resistant receptacles.
Additionally, the term “nonlocking” was added to describe the types of receptacles to which this rule is intended to apply. Only those receptacles that are of the straight blade configuration will be required to comply with this section.
A new requirement for tamper-resistant receptacles in guest rooms and guest suites was added.
406.13 Tamper-Resistant Receptacles in Guest Rooms and Guest Suites. Nonlocking-type 15A and 20A, 125V receptacles in guest rooms and guest suites must be listed as tamper-resistant.
Analysis: Guest rooms and guest suites often have children staying in them, so tamper-resistant receptacles have been added as a requirement for these locations. Guest suites that provide complete facilities for living, sleeping, cooking and sanitation are considered to be dwelling units by the NEC, and as such were already required to provide tamper-resistant receptacles. This change will now require tamper-resistant receptacles in all guest rooms and guest suites.
A new requirement for tamper-resistant receptacles in “child care facilities” was added.
406.14 Tamper-Resistant Receptacles in Child Care Facilities. Nonlocking-type 15A and 20A, 125V receptacles in child care facilities must be listed as tamper-resistant.
Analysis: The definition for “child care facilities” in 406.2 deals with children of 7 yr of age and younger. Many of these younger children spend a great deal of time in child care facilities as well as in homes, yet the 2008 NEC only required tamper-resistant receptacles in dwelling units. Proponents of these devices immediately began hoping for expansion of these receptacles to other areas that are full of children. With this change, areas such as schools and day care facilities will be forced to use them. Other areas that aren’t quite as clear, however, include hospitals and other medical centers.
A new section will require a disconnecting means for most transformers.
450.14 Disconnecting Means. For transformers other than Class 2 and Class 3, a means is required to disconnect all transformer ungrounded primary conductors. The disconnecting means must be located within sight of the transformer unless the location of the disconnect is field-marked on the transformer and the disconnect is lockable. (click here to see Fig. 17)
Analysis: Although many Code users have believed that this requirement already existed, in previous NEC editions transformers were one of the only pieces of equipment that didn’t require a disconnecting means. Although there were no documented injuries to warrant this change, it’s hard to argue that this requirement doesn’t enhance safety.
Receptacles with insulated grounding terminals are no longer allowed in a patient care area.
517.16 Receptacles With Insulated Grounding Terminals. Receptacles having insulated grounding terminals (isolated ground receptacles) [250.146(D)] aren’t permitted to be installed in patient care areas. (click here to see Fig. 18)
Analysis: In a rather substantial change to the health care provisions, isolated ground receptacles are no longer permitted in patient care areas. The wiring method in these locations requires two equipment grounding conductors — one of the wiring method type; the other in the form of an insulated green conductor [517.13]. Using an isolated ground receptacle defeats the entire concept of this dual equipment ground concept by effectively removing the metal wiring method equipment grounding conductor. In these areas, the patient is often involved in an invasive procedure, meaning the human skin is broken, typically by an incision. When this is the case, the patient is much more vulnerable to electric shock. In fact, current applied directly to the circulatory system of the patient can easily cause death at current levels lower than even a GFCI will protect against. Previous editions of the NEC included an Informational Note telling the Code user that the use of these receptacles was a bad idea in these areas. With this change, the Code rule now recognizes that fact and prohibits the practice altogether.
The requirements for swimming pool bonding were revised…again.
680.26(B)(2) Perimeter Surfaces. An equipotential bonding grid must extend 3 ft horizontally beyond the inside walls of a pool, outdoor spa, or outdoor hot tub, including unpaved, paved, and poured concrete surfaces. Perimeter surfaces less than 3 ft that are separated by a permanent wall or building 5 ft in height or more require an equipotential bonding grid on the pool side of the permanent wall or building.
The bonding grid must comply with (a) or (b) and be attached to the conductive pool reinforcing steel at a minimum of four points uniformly spaced around the perimeter of the walls of a pool, outdoor spa, or outdoor hot tub.
(a) Structural Reinforcing Steel. Unencapsulated structural reinforcing steel in concrete shells secured together by steel tie wires [680.26(B)(1)(a)].
(b) Alternative Copper Conductor Grid. Where the structural reinforcing steel isn’t available (or is encapsulated in a nonconductive compound, such as epoxy), an equipotential bonding grid meeting all of the following requirements must be installed (click here to see Fig. 19):
(1) The bonding grid must be 8 AWG solid copper, arranged in the manner described in 680.26(B)(1)(b)(3).
(2) The bonding grid must follow the contour of the perimeter surface extending 3 ft horizontally beyond the inside walls of pool.
(3) Listed splicing devices must be used.
(4) The grid must be secured in or under the deck or unpaved surface within 4 in. to 6 in. of the underside of the deck.
(3) Metallic Components. Metallic parts of the pool, outdoor spa, or outdoor hot tub structure must be bonded to the equipotential grid.
(4) Underwater Metal Forming Shells. Metal forming shells and mounting brackets for luminaires and speakers must be bonded to the equipotential grid.
(5) Metal Fittings. Metal fittings sized 4 in. and larger that penetrate into the pool, outdoor spa, or outdoor hot tub structure, such as ladders and handrails, must be bonded to the equipotential grid.
(6) Electrical Equipment. Metal parts of electrical equipment associated with the pool, outdoor spa, or outdoor hot tub water circulating system, such as water heaters and pump motors and metal parts of pool covers, must be bonded to the equipotential grid.
Ex.: Metal parts of listed double insulation equipment isn’t required to be bonded to the equipotential grid.
(a) Double-Insulated Water-Pump Motors. If a double-insulated water-pump motor is installed, a solid 8 AWG copper conductor from the bonding grid must be provided for a replacement motor.
(b) Pool Water Heaters. Pool water heaters must be grounded and bonded in accordance with equipment instructions.
(7) Fixed Metal Parts. All fixed metal parts must be bonded to the equipotential grid, including but not limited to metal-sheathed cables and raceways, metal piping, metal awnings, metal fences, and metal door and window frames.
Ex. 1: If separated from the pool, outdoor spa, or outdoor hot tub structure by a permanent barrier that prevents contact by a person.
Ex. 2: If located more than 5 ft horizontally of the inside walls of the pool, outdoor spa, or outdoor hot tub structure.
Ex. 3: If located more than 12 ft measured vertically above the maximum water level.
(C) Pool Water. Pool water must have an electrical connection to one or more of the bonded parts described in 680.26(B). If none of the bonded parts is in direct connection with the pool water, the pool water must be in direct contact with an approved corrosion-resistant conductive surface that exposes not less than 9 sq in. of surface area to the pool water at all times, and it must be bonded in accordance with 680.26(B). (click here to see Fig. 20)
Analysis: This section has been revised extensively over the last few Code change cycles, and this one is no exception. Recent revisions have left gaping holes in the requirements not to mention plenty of room for misunderstanding, misinterpretation, and misapplication. The changes in the 2011 edition of the NEC seek to remedy these problems.
The connection of the copper bonding grid discussed in 680.26(B)(1)(b)(1) has been addressed. When nonconductive structural reinforcing steel is used in a pool, a bonding grid of 8 AWG copper conductors is required, but previous editions of the Code didn’t address how to connect the grid to itself. This NEC cycle clarifies that the grid must be bonded together at all points of crossing in the grid, and the bonding means must comply with the connection provisions of 250.8. Also, 680.26(B)((2)(b) was revised, requiring a copper grid instead of the single conductor permitted in 2008. Fortunately, this provision isn’t used often as it would be an incredibly time consuming and expensive solution.
A clarification was also made regarding the bonding of the pool deck. It isn’t uncommon for a pool deck to be less than 3 ft when a wall, fence, or other structure is near the pool. Previous editions of the Code didn’t tell the user how to handle the situations, but now it’s clear that the bonding doesn’t need to extend to the other side of the wall, provided the wall (or fence) is no less than 5 ft in height.
The bonding of nonelectric metal parts has been clarified. Section 680.26(B)(7) has long required that “metal wiring methods and equipment” be bonded to the equipotential grid discussed in this section. One question that often comes up, however, is whether the “equipment” contemplated in this rule applies to only “electrical equipment,” as defined in Art. 100 — or if it’s intended to apply to all equipment, including nonelectrical equipment. This change clarifies that this provision does, in fact, apply to nonelectrical equipment, such as metal fences and similar items.
Lastly, the exception allowing for a permanent barrier separating metal parts has been clarified. A change to the exception makes it clear that such a barrier must prevent a person from contacting metal parts and equipment that aren’t bonded.
The accessibility of the receptacle supplying a hydromassage tub has been revised.
680.73 Accessibility. Electrical equipment for hydromassage bathtubs must be capable of being removed or exposed without damaging the building structure or finish. Where the hydromassage bathtub is cord-and plug-connected with the supply receptacle accessible only through an access opening, the receptacle must face toward the opening and be within 1 ft of the opening.
Analysis: When a hydromassage tub is cord- and plug-connected, it isn’t uncommon to find the receptacle beneath the tub arranged in a manner that makes it nearly impossible to see, much less use. Oftentimes, these receptacles are several feet away from the access opening, facing away from the person trying to access the receptacle. This change now requires that such a receptacle be installed close to the access opening (within 1 ft), and it must also be facing toward the opening.
The requirements for PV grounding electrode systems have been greatly revised.
690.47 Grounding Electrode System.
(B) Direct-Current Systems. If installing a DC system, a grounding electrode system must be provided in accordance with 250.166 with a grounding electrode conductor in accordance with 250.64.
A common DC grounding-electrode conductor is permitted to serve multiple inverters with the size of the common grounding electrode and the tap conductors in accordance with 250.166. The tap conductors must be connected to the common grounding-electrode conductor in such a manner that the common grounding electrode conductor remains without a splice or joint.
(C) Alternating-Current (AC) and Direct-Current (DC) Grounding Requirements. PV systems with DC modules having no direct connection between the DC grounded conductor and AC grounded conductor must be bonded to the AC grounding system by one of the methods listed in (1), (2), or (3).
Note 1: ANSI/UL 1741, Standard for Inverters, Converters, and Controllers for Use in Independent Power Systems have the grounding electrode conductor (GEC) connection point identified. In PV inverters, the terminals for the DC and AC equipment grounding conductors common with each other are marked DC GEC terminal.
Note 2: For utility-interactive systems, the existing premises grounding system serves as the AC grounding system.
(1) Separate DC Grounding Electrode System Bonded to the AC Grounding Electrode System. A separate DC grounding electrode bonded to the AC grounding electrode system with a bonding jumper sized to the larger of the existing AC grounding electrode conductor or DC grounding electrode conductor specified by 250.166.
The DC grounding electrode conductor or bonding jumper to the AC grounding electrode system can’t be used as the required AC equipment grounding conductor.
(2) Common DC and AC Grounding Electrode. A DC grounding electrode conductor sized in accordance with 250.166 run from the marked DC grounding electrode connection point to the AC grounding electrode. (click here to see Fig. 21)
Where an AC grounding electrode isn’t accessible, the DC grounding electrode conductor is permitted to terminate to the AC grounding electrode conductor by irreversible compression-type connectors listed as grounding and bonding equipment or by the exothermic welding process [250.64(C)(1)].
The DC grounding electrode conductor or bonding jumper to the AC grounding electrode system can’t be used as the required AC equipment grounding conductor.
(3) Combined DC Grounding Electrode Conductor and AC Equipment Grounding Conductor. An unspliced, or irreversibly spliced, combined equipment grounding/grounding electrode conductor run from the marked DC grounding electrode connection point along with the AC circuit conductors to the grounding bus bar in the associated AC equipment.
The combined equipment grounding/grounding electrode conductor must be sized to the larger of 250.122 or 250.166 and be installed in accordance with 250.64(E).
Analysis: Section 690.47(B) has been revised to clarify that a common grounding electrode conductor can be used to ground multiple inverters. This concept isn’t new to the Code, as similar provisions can be found in 250.30 for separately derived systems.
As can be seen rather easily, (C) has been extensively revised again. Changes to this edition of the NEC are intended to incorporate the concepts of the 2005 and 2008 editions into clear, easily understandable text.
In a somewhat surprising change, 690.47(D) was deleted. That section required that ground and pole-mounted PV arrays have a grounding electrode. This requirement was added in the 2008 edition and was intended to be optional. The Code language that was used, however, made it mandatory. By removing the rule altogether, it’s still optional, but now isn’t mandatory.