Illustrated Changes In The 1999 NEC — Part 3 of 4

A new NEC is on tap, with major changes in how the document presents the material, even changing to a new full-page format. This analysis of the changes represented in the 1999 edition of the National Electrical Code (NEC) covers the most significant of the many changes. Some are indeed major, including two new articles, (with another article deleted). Others involve only minor editorial issues. Major

A new NEC is on tap, with major changes in how the document presents the material, even changing to a new full-page format.

This analysis of the changes represented in the 1999 edition of the National Electrical Code (NEC) covers the most significant of the many changes. Some are indeed major, including two new articles, (with another article deleted). Others involve only minor editorial issues. Major or minor, if you are involved with the particular subject matter, the most minor changes can assume major proportions in unexpected ways. Every proposal was made for a reason, and this magazine article is no substitute for careful study of the Code itself.

Sec. 500-1 and the article title no longer reference Art. 505. As referenced in a new (FPN), Art. 505 now exists as a stand-alone article, and all requirements pertaining to the zone classification system in Art. 500 through 504 have been relocated or reiterated in Art. 505.

Sec. 501-5(a)(2). Conduits entering a purged and pressurized enclosure in a Class I Division 1 location, assuming the conduit is not pressurized as part of the protection system, need to be sealed within 18 in. of the enclosure entry. Pressurization will protect the conduit from pressurized equipment, but only the explosionproof seal will protect the equipment enclosure from a flame front moving outward from an occurrence elsewhere within the conduit system.

Sec. 501-5(b)(2). Class I Div. 2 boundary seals must be within 10 ft of the boundary. The same change for Div. 1 was made in the 1996 NEC. Proximity to the boundary doesn't matter if the wiring system after or ahead of (depending on the seal position) the seal cannot receive or discharge hazardous vapors. An unbroken length of conduit is exactly so.

Sec. 501-5(c)(3). This refers to the size of the fitting instead of the conduit, in order to get a proper seal in cases where an oversize seal has been used. Oversize seals, made up with reducers, are common with the 25% fill restrictions. However, the fittings are tested based on their trade size. Filling a seal based on a reduced raceway size could cause the seal to fail.

Sec. 501-5(c)(6). The 25% fill rule for seals now refers specifically to rigid metal conduit, since IMC can also be used for these areas, and it has a larger cross-sectional area. The basic seal research was done under the 1968 NEC, prior to the introduction of Type IMC conduit into the Code (1975) and into hazardous locations (1978).

Sec. 501-6(b)(4). This paragraph, which allowed for up to 10 overcurrent devices in general-purpose enclosures in Class I Div. 2 areas (serving fixed lighting only), has been deleted.

The result will be to revert to the provisions of Sec. 501-6(b)(1), which requires special provisions for even one circuit breaker or fuse. This allowance has been in the NEC since 1947; there has never been a Div. 2 classified area that didn't have this permission (the Division provisions came in 1947). The only substantiation for removing it was: Why 10 overcurrent devices and not 11? That's awfully thin for something that's been in place for 52 years.

Sec. 502-4(b) Ex. 2. A new exception allows cables that were listed for use in Class II Div. 1 areas to run in cable tray in Div. 2 areas without the customary spacing between cables. There still is no substitute for good housekeeping in these dust-prone environments. The cable tray type isn't addressed in the exception, which means you need to comply with the main rule. You can't do this with a solid-bottom tray. The rule only recognizes ladder, ventilated trough, or ventilated channel cable trays.

Sec. 505-4. This is a new section, and it sets out the various protection strategies for use with the zone system. It corresponds to Sec. 500-4. The drawing shows just one example of a protective scheme commonly used for lighting, increased safety as covered in Sec. 505-4(f). A detailed analysis of all of the protective systems is beyond the scope of this analysis.

Sec. 505-6(a). A qualified P.E. (registered professional engineer) still needs to supervise zone applications, but the rule has been relocated here from Sec. 500-3. This assures accountability on the part of the professional charged with the design responsibilities for these systems. The rule was relocated in the process of converting Art. 505 to a fully stand-alone article.

Sec. 505-6(b). Zone classifications cannot be mixed with Division classifications. However, a Class I Zone 2 area may abut (but not overlap) a Class I Division 2 area. The original concept for the zone classification system was that it was never supposed to be a "mix and match" type of system. It was supposed to be applied to an entire facility or perhaps after a major renovation. However, such wording never made it into the 1996 NEC. Instead, it was added as a TIA (tentative interim amendment). It now appears as permanent Code.

Sec. 505-6(c). A division-classified area may be reclassified under the zone system, provided all the space classified on the basis of a single hazardous source gets reclassified. This may be a solution to the "mix and match" problem if zone equipment must be brought into an area previously classified under the division concept. Sec. 505-15(b), for example, recognizes all Div. 1 wiring methods for Zone 1, and Sec. 505-20(b) Ex. makes a similar allowance for equipment. However, if any of the division-classified environment falls into Zone 0, you will have to remove any nonintrinsically safe equipment and circuits from that area to qualify under Sec. 505-15(a) and 505-20(a) Ex.

Sec. 505-10. This section on marking is greatly expanded to incorporate the protection techniques in Sec. 505-4 and provide a consistent marking protocol that interrelates those techniques to the applicable zones and gas groups.

It allows for equipment produced for the traditional system to have additional markings for zone, gas group, and temperature rating-without going further. On the other hand, if the equipment was produced for zone-classified areas originally, it has to be marked under the new procedures. The temperature rules [paragraph (3)] use the same table as the prior Code, but include refinements including rules on nonstandard ambient temperatures, a reiteration of Sec. 500-5(d) Ex. 1 for nonheating or low-heat equipment, and correlation with Sec. 505-20(b) and (c).

Part of the zone evaluation system involves the protective scheme the manufacturer anticipates. A new paragraph sets out what procedures may be valid in what environments. For example, equipment with "increased safety" should work in all Group II locations, but "flameproof" equipment must be marked Group IIA [or IIB or IIC, depending on specific gas or vapor, and as listed in new Table 505-10(b)(2) for gas classification groups]. As in the prior Code, temperature limitations [in Table 505-10(b)(3)] must be applied. Fig. 505-10(b)(1) (apparently misidentified by the panel) is supposed to constitute the "explanation of the marking that is required" to which Sec. 505-10(b)(2) (FPN No. 2) refers.

Sec. 505-15(b). This continues the rules for Zone 1 wiring methods, in that all Class I Div. 1 wiring methods can be used. The rules for sealing are more comprehensive, and tie in with the protection strategies available in Sec. 505-5. Fine print notes address "ingress protection" issues that arise in using enclosures evaluated under the zone system.

The seal requirements for increased safety applications don't reflect any need to protect the conduit from the increased safety equipment. The explosionproof seal is there, similar to pressurized enclosures as covered in the change in Sec. 501-5(a)(2), to protect the equipment enclosure from a flame front moving outward from an occurrence elsewhere within the conduit system.

Sec. 505-21. This is an entirely new section addressing motors using the "increased safety" protection protocol.

There are specific rules regarding how manufacturers need to mark these motors and their controllers, as well as installation requirements to use the prescribed terminals listed with the motor (these designs are essential to the "increased safety" provisions). Special overload protection rules supersede allowances in Sec. 430-34 and 430-44 for increased overload settings and overload waiver with alarms for orderly shutdowns. In addition, you cannot employ shunting during starting, as covered in Sec. 430-35.

Sec. 514-6. Each dispensing device must now have means to remove all external voltage sources, including those in any applicable control circuit-even through "feedback."

This is a new section for maintenance and repair purposes of dispensing equipment. It primarily addresses control circuit design and routing. The idea is to be able to work safely on a single dispenser without shutting down the others. Increasingly, the dispensers are for control and dispensing only; the pumps are remote.

Sec. 517-3 (Emergency System). This revised definition adds a clause recognizing Art. 517 can amend the general provisions in Art. 700 for emergency systems. Sec. 517-30(b)(4) allows a single transfer switch in small hospitals to supply both the life safety and critical branches (emergency system loads) and equipment system (usually other than emergency system loads). This violates Sec. 700-6(c), resulting in what used to be a conflict that has been resolved.

Background: The change resolves other conflicts as well. Sec. 517-30(d) sizes emergency generator capacity differently than some interpretations of Sec. 700-5(a). Sec. 517-30(b)(5) allows nonessential loads on the hospital generating facilities, provided there is a separate transfer switch for these loads. Regardless of the amount of such load, there has to be automatic load shedding arranged such that if the nonessential load threatens the ability of the generator to support the essential load, the nonessential load will be shed. This does not agree with Sec. 700-5(b), which only requires automatic load shedding "as needed for other occupancies." That means no automatic load shedding in cases where the generator has been sized to accommodate the combined load. The change in Sec. 517-3 resolves all of these conflicts.

Sec. 517-13(a) (Ex. 3). In addition to the existing allowance for light fixtures over 71/2 ft above the floor, this exception is broadened so switches located outside a patient vicinity may omit the insulated equipment grounding conductor at the device enclosure. EC&M tip: Be careful not to read more into this exception. These circuits still must meet the redundant grounding rules in the next subsection. That means the exception makes no change in wiring method selection. Only after you spend the time installing metallic wiring methods do you get to use this trivial allowance to omit the insulated equipment grounding conductor. This exception has been referred to as the "thanks for nothing" exception. Although clearly unintended, note the literal text would allow such a switch within an adjacent patient vicinity.

Sec. 517-18(c). The requirement for tamper-resistant receptacles or a cover limiting improper access has been modified to require, in the case of the cover, that it be a listed tamper-resistant cover, in other words, specifically listed for tamper-resistant applications. The provision about limiting improper access in the prior Code was impossible to enforce. The listing requirement will assure such covers meet a consistent standard.

Sec. 517-33(c). A new subsection requires all receptacles connected to the critical branch to be readily recognizable as such, either by color or marking.

The facility can choose whether to use distinguishing features of the receptacles or the faceplates as the basis for recognition. This has been a requirement in the NFPA Health Care Facilities Standard (NFPA 99) for a long time. Now that it's in the NEC, it will be more widely enforced.

Sec. 518-2(c). The three main divisions in this section now have subsection titles. The substantive issue is here: In addition to referencing Art. 520 for the wiring for the stage area of a place of assembly, the associated audience seating areas are now included as well. Therefore, a place of assembly with a "stage platform or area" for the presentation of "theatrical or musical production" now moves out of Art. 518 entirely, and Art. 520 governs.

Background: This was never an issue until the 1996 NEC, when NFPA Standards Council, over the objections of the panel, imposed what is now Sec. 518-4(c). This allows for the use of nonmetallic wiring methods behind a fire finish in some places of assembly. Until the 1996 NEC, the allowable wiring methods didn't significantly differ between Art. 518 and Art. 520. However they do now. You must view this change in the context of that development.

After the 1996 NEC came out, the EC&M Code Forum department fielded a question, asking whether the presence of a small stage area in a conference room would void the allowance for using ENT in Sec. 518-4. We said Art. 520 applied to the stage and theatrical equipment, but not to the general wiring in the conference room (the "audience seating areas").

This change, which negates the basis for our opinion, also circumvents the Council decision in almost every conference facility, many restaurants, and in the overwhelming majority of occupancies where it was being applied. Certainly relatively few facilities with occupancy loads of 100 or more don't have stage/platform areas.

Sec. 518-4(a). This section now recognizes type AC cable for the first time as a general wiring method for places of assembly, provided it is the type with a separate equipment grounding conductor, similar to that recognized in Sec. 517-13(a) Ex. 1. The section also recognizes "flexible metal raceways" for the first time.

Background: This section has always recognized Type MC cable for assembly area wiring. When these rules were first written, Type MC cable was customarily used in industrial occupancies primarily in very large feeder sizes. This section never really caught up with the fact that today's Type MC cable can be a 14-2 interlocking-armor branch circuit with 17 mil armor. Meanwhile, Type AC cable in any size, with its 25 mil armor, was strictly forbidden. This change is a first step in establishing some rational consistency between the treatment of these two closely related wiring methods.

Sec. 525-13(d). The blanket prohibition against cord connectors lying on the ground has been significantly modified. Now such connectors can be laid on the ground if they are listed for wet locations. In addition, you can't set any such connector in audience traffic paths or locations otherwise accessible to the public, unless you've suitably guarded it. EC&M tip: Be sure the design you choose is really suitable for this type of exposure (some are almost bombproof).

Sec. 525-18. The rules for GFCI protection are much stronger, with all 15A and 20A 125V receptacles covered, either inherently or through the use of cord sets with integral GFCI protection. Egress lighting cannot be connected to the load side of a GFCI receptacle, however. There is also a GFCI waiver for appliances, such as refrigeration and heating equipment, that are "incompatible" with GFCI protective devices. All other receptacles, of any amperage or voltage, must either be GFCI protected or covered by an assured equipment grounding conductor program (AEGCP) in accordance with Section 305-6(b).

This is a major change correlating with changes in Sec. 305-6, except 30A 125V receptacles didn't make the mandatory GFCI list. Some refrigeration (generally the defrosting part) and cooking equipment have heaters that routinely pass small amounts of current to the grounded shell of the heating element until they get hot. This equipment nuisance trips GFCI devices. AEGCP coverage is new to this article.

Sec. 525-40. This new section, in a new Part E covering "Attractions Utilizing Pools, Fountains, and Similar Installations with Contained Volumes of Water," makes the applicable requirements in Art. 680 apply to duck ponds, dousing tanks, decorative fountains, etc. Art. 680 has requirements in Part A, although the extent to which each particular requirement was considered by this panel is questionable. The drawing (below) shows one plausible application. Note the section wording doesn't mention what it covers; you need to look at the title of the new Part E of the article to decide.

Sec. 547-8. This section now presents three alternative methods for arranging electrical distribution on a farm supplied through a distribution point, which has now been defined at the end of the section. The distribution point is a centrally located electrical supply structure from which services or feeders to agricultural and other buildings, including the associated farm dwelling, are normally supplied.

a)Service conductors can go to multiple buildings from the distribution point, in which case the normal service rules apply, although some form of disconnect (presumably a pole-top isolating switch) must be installed at the distribution point, but not necessarily readily accessible. This pole-top switch would not be a service disconnect. This subsection indicates that by expressly saying Sec. 250-24 applies, a rule that only applies to grounding at services.

b) A conventional service can terminate at the pole, with overcurrent-protected feeders running, under normal Code rules, to building disconnecting means at each farm building, including the farmhouse. This is seldom done, partly due to the relative exposure of the service and distribution equipment.

c) A pole top disconnect, suitable for use as service equipment but without overcurrent protection, can go at the pole. In this case, you can't make any downstream connections between grounded and grounding conductors. The equipment grounding conductor must also be sized the same as the largest ungrounded conductor. This basic arrangement is common, but severe problems in the panel wording will require careful consultation with the AHJ. First, current UL standards anticipate overcurrent protection within or adjacent to the disconnect, in accordance with Sec. 230-91. This provision, in Chapter 5, is a valid exercise of Sec. 90-3 to effectively amend Sec. 230-91, but no pole-top disconnect is listed or could be listed as service equipment without a full revision of the applicable standard. The panel failed to properly research this point. In addition, the literal text requires a four-wire drop with a full-sized equipment grounding conductor to each building including the farmhouse, which is never done. The procedure has only been applied to barns and similar structures used directly in agriculture.

A major safety issue arises because this subsection creates a new concept: Feeders without overcurrent protection, but without any rules for routing these conductors. For example, parts of Art. 230 might be applied. The definition of distribution point, though it appears in this subsection, was located incorrectly and should apply to the entire section.

Substantial experience supports the concepts presented in this rewritten material. This subsection is, in effect, the former Sec. 547-8(a) Ex. 1, in positive text. This is what the agricultural engineers had in mind when they created that exception. However, the panel completely failed to adequately address the implications of making the sort of amendments to Chapter 2 implicit in this new wording.

With agreement of the local inspector, probably the most appropriate way to apply this is first to treat the unprotected feeder conductors as if they were service drop conductors. However, they aren't service conductors and they need to carry a separate equipment grounding conductor with them. Second, you'll need approval to use the existing pole-top equipment even though it isn't listed. This equipment has been used in this way for many years, and that sort of approval should be recognized. Third, you'll want to explore the possibility of wiring the farmhouse 3-wire, which you could do as long as you don't violate Sec. 250-32(b)(2). If, for example, there is a common metallic water service between the barn and the house, then regrounding the neutral at the house disconnect would be a violation, and going 4-wire to the house would be the only alternative.

Sec. 547-9. The equipotential plane made mandatory in the 1996 NEC has been fine tuned.

  • The voltage gradient ramps "may" only be required at entrances traversed daily by the same livestock. A new fine print note advises that natural voltage gradients exist at the margins of equipotential planes, and if the gradient exceeds 1V per ft, the voltage gradient will be necessary.

    Putting the fine print note (which has mandatory language) together with the rule that says "may," we have what might be a requirement. In this case, it appears the panel's intent is to require a voltage gradient ramp if the gradient exceeds 1V per ft. However, the status of that parameter as a fine print note, in combination with the word "may" in the rule (also very improper), makes this something to discuss with the AHJ. The phrase "crossed daily by the same livestock" addresses the problem of livestock learning that there is a tingle voltage and eventually refusing to go in or out of the building.

  • Correcting an error, the equipotential planes may be omitted all together at buildings without electric service or without metallic equipment that is likely to become energized while accessible to livestock. If the equipotential plane includes floor elements that support a slatted floor, the slatted floor elements don't require bonding.

  • Where you do have an equipotential plane, a new rule requires GFCI protection of all 125V 15A and 20A receptacles in the area.

Sec. 551-72. Now 120V RV sites can be supplied from three-phase grounded distributions; only 50A 120/240V sites must be supplied from single-phase distributions. This allows utilities to better balance loads, and it allows ready access at such parks to 3-phase power for non-site power requirements.

Sec. 555-4. This new section requires a readily accessible disconnecting means to be provided so each boat can be isolated from its supply circuit, consisting of a switch or circuit breaker or both and located within sight of the shore power connection. It is intended to cut off the supply to the boat. This rule applies in addition to the receptacle, which is often considered to have a disconnecting function. This new rule brings into the NEC Sec. 3-15 of NFPA 303.

Sec. 555-6. The demand calculations for marina loads changed in several important ways. The allowance for an installation of 100 receptacles or more with a 20% demand factor is deleted; now the most favorable demand occurs for more than 70 receptacles, figured at 30% demand.

However, new subsections allow for modifications to these demand calculations.

  • First, if shore power accommodations at a particular slip include two voltages (including, for example, a 30A 125V and a 50A 125/250V receptacle) then only the largest need counted in the demand calculations.

  • Second, if each slip has individual power meters, then an additional 10% reduction can be applied to the overall demand calculation from the table.

Sec. 600-7. This section underwent massive changes, in part to correct numerous technical errors that crept in during the Standards Council actions on appeals on the 1996 NEC.

  • Up to 100 ft of greenfield or liquidtight flexible metal conduit can be used in a bonding path to sign elements. The currents involved are very low, and the 100 ft distance was investigated by a testing lab and found suitable. This is a Chapter 6 amendment to Sec. 250-118(6)(c).

  • Small metal parts not exceeding 2 in. in any dimension and spaced at least three quarter inches from neon tubing don't require a bonding connection. This removes such incidental equipment as the metal feet on tubing support clips.

  • Bonding conductors must be copper and at least No. 14. This rule was modified and relocated from its former location as Sec. 250-97. As relocated, this provision no longer recognizes the use of an aluminum bonding conductor.

  • If a nonmetallic wiring method encloses secondary wiring from a neon transformer or power supply, the bonding conductor must run outside the conduit spaced at least one and a half inches distant for power supplies running below 100 Hz, and one and three quarter inches away for higher frequencies. This provision, unique in the history of the NEC, has been well substantiated. Separating the grounding conductor reduces the intensity of the voltage gradient, which in turn reduces corona. There have been fires produced from the deterioration of the GTO cable from corona discharges. Obviously this separation isn't possible in a metal raceway. The metal raceway distributes the ground plane equally around the conductor. In addition, Sec. 600-32(j) more severely limits the allowable length on metal raceways to the first neon terminal (to 20 ft instead of 50 ft). Most of the voltage problem occurs in this particular segment of the secondary wiring system.

  • As in Sec. 250-136(a), you can't use metal parts of buildings as an equipment grounding conductor for this purpose.

Sec. 600-32(a). ENT can't be used as a high-voltage sign secondary wiring method. If a nonmetallic wiring method encloses secondary wiring from a neon transformer or power supply, the wiring method must be spaced from grounded elements of the building at least one and a half inches distance for power supplies running below 100 Hz and one and three quarter inches away for higher frequencies. ENT (but not liquidtight flexible nonmetallic conduit!) was disallowed out of concern it would sag and lose the required spacing.

Sec. 625-29(d). This section, covering required mechanical ventilation, has been completely restructured.

  • In all cases where listed EV charging equipment is in use for indoor charging of EVs that require ventilation, mechanical ventilation must be provided, such as a fan. Positive pressure ventilation systems are only permitted in buildings or areas that have been specifically designed and approved for that application.

  • Three methods follow that constitute the permitted methods of ventilation design. The first two reflect current procedures for using either the table or formula method, including the allowance for 15A and 20A 120V equipment that is switched with the ventilation system. A new procedure allows the ventilation to be part of the overall ventilation design for the building, provided the design is part of a qualified engineering study.

    The final two paragraphs (on interlocking the ventilation system with vehicle supply equipment and 125V 15A and 20A receptacles) that follow (3) on engineering supervision appear to apply to all of subsection (d). This confusion resulted from the conversion of the former exception into normal text.

Art. 630. The rules for motor-generator arc welders and AC transformer and DC rectifier arc welders have been combined into a single set of rules, allowing the deletion of the former Part C of Art. 630 and the relettering of the remaining parts.

Art. 640. This article, now titled "Audio Signal Processing, Amplification, and Reproduction Equipment," has been completely rewritten, taking it from the vacuum tube technology of the 1950s to today. No former requirements have survived to any significant extent.

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.