Illustrated Changes In The 1999 NEC — Part 2 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 only the most significant of the many changes. Some of these changes are indeed major, including two new articles, (with another article deleted) and others are included

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 only the most significant of the many changes. Some of these changes are indeed major, including two new articles, (with another article deleted) and others are included for minor editorial reasons. Major or minor, if you are involved with the particular subject matter the most minor change 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. 362-6. Multiple conduit or cable entries to a wireway and enclosing the same conductor (No. 4 or larger) must be spaced at least six times the trade diameter of the largest entry apart.

The point of this section has always been to ensure there is adequate space for deflection of conductors without damaging insulation. That's why, when you deflect conductors more than 30 degrees in a wireway, you have to be sure the minimum distances in Sec. 373-6 are available. This change also addresses the related case where an installer enters one side of a wireway and then exits the other. Now, the wireway is being used as a pull box. If it were a pull box, Sec. 370-28(a)(2) would require a minimum raceway separation distance of six times the nominal raceway diameter, and now the same requirement applies to the wireway.

It remains true the minimum width of the wireway follows Sec. 373-6 and not the six-times rule in Sec. 370-28(a)(2). This admitted compromise reflects the fact that usually you have the opportunity to lay long lengths of conductors into a wireway section; working with the longer lengths is easier to do and stresses the insulation less.

Sec. 364-6(b)(2). For vertical busway risers penetrating two or more dry floors in other than industrial occupancies, now you'll have to provide curbing around the penetrations. The curbing has to be at least 4 in. high, and it can't be more than 12 in. from the floor opening. Other electrical equipment must be located so it won't be damaged by liquids retained by the curb.

Background: In high-rise construction, busway risers often pass through janitor's closets with floor-level slop sinks and hoses. Normally the floor penetration would be firestopped, in accordance with Sec. 300-21. Depending on the configuration of the firestopping, however, floor liquids might easily reach and flood the vertical busway. Also, other electrical equipment in the room suitable for ordinary locations shouldn't be on or near the floor, where it might get flooded by whatever fluids get held back by the curbing. This rule may or may not be meaningful depending on whether the floor is horizontal relative to any gaps under the door(s), etc.

This change has to be read in its larger context. Sec. 364-6(b)(1) only permits floor penetrations through dry floors, and both paragraphs apply to this work. Don't infer that because this paragraph refers to dry floors, you could do something different or less restrictive on a wet floor. The first paragraph also continues the rule requiring unventilated, totally enclosed busways up to the 6-ft level to prevent physical damage.

Sec. 370-23(d). New rules cover box supports in suspended ceiling cavities. The box can't be larger than 100 cu. in., and the installation must comply with Sec. 300-11(a). The support wires must be fastened at each end so as to be taut within the ceiling cavity.

Background: For many Code cycles, this section and Sec. 300-11(a) have been at odds over the support rules for boxes in ceiling cavities. Sec. 300-11(a), ever a moving target, has allowed boxes on support wires in some form and under some conditions, but also under rules that have been changing from cycle to cycle. In contrast, the rules in Sec. 370-23 always required rigid support, and suspended ceiling support wires flunk that requirement.

What happened: This cycle, CMP 9 mostly, but not entirely, unloaded the problem. It basically said the box support had merely to comply with Sec. 300-11(a). It did, however, add two requirements that would be unique to enclosures covered in Sec. 370-23. First, the support wires used to support the enclosure need to be taut. Second, the enclosure can't exceed 100 cu. in., which coincides with the other size thresholds in Sec. 370-23. As long as CMP 3 doesn't expressly allow slack support wires or boxes over 100 cu. in., the old conflicts won't return.

The exceptions now clearly apply to conduit bodies over 100 cu. in., and they also address "E" fittings for the first time, clearing up areas of confusion.

EC&M tip: Don't confuse the wording of the exceptions addressing "E" fittings ("conduit body constructed with only one conduit entry") as applying to other conduit bodies such as LBs with only one conduit support in use. With the sole exception of the "E" fitting, the rules continue to disallow any support of enclosures by a single conduit entry.

Sec. 370-27(a) Ex. This new exception allows up to 6-lb wall-mounted fixtures (not exceeding 16 in. in any dimension) to be hung on device boxes with no fewer than two No. 6 or larger screws.

Background: The basic rule requires boxes used to support fixtures to be "designed" for this purpose. Evidence of such design, per UL, is found on the smallest unit shipping carton, which must be marked "FOR FIXTURE SUPPORT." Those boxes have 8-32 or larger screws. That made what has become a routine use of device boxes to hang small "peanut butter jar" fixtures technically in violation of the Code. The parameters in the new exception are taken from Sec. 410-15(a), which allows a lamp screw shell to support a small fixture. If the screw shell of a light bulb can support such a fixture, surely two screws can as well.

However, the 1998 UL Electrical Construction Materials Directory (the "Green Book") has just complicated the issue. For the first time, it allows device boxes, whether new or old-work ("intended to be installed in an existing structure"), metallic or nonmetallic, to support smoke detectors, carbon monoxide detectors, and fixtures, not over 15 lb, and without any restriction as to wall or ceiling applicability [emphasis supplied]. In view of the panel action this may be revised. But until then, it has official recognition.

Since it basically declares them as having been adequately designed for the support of up to 15 lb fixtures in any orientation, it effectively supersedes the restrictions on weight and orientation on device boxes. That statement by UL moves device boxes into compliance with the main rule. Therefore, the exception, being permissive, ends up a nullity with respect to device boxes. However, you should continue to apply the conditions in the exception, even to device boxes, and even though they are more restrictive. The UL product directories change once a year, and this one may promptly get back in line with the NEC.

Art. 370, Part D. A new part of Art. 370 now covers "Manholes and Other Electric Enclosures Intended for Personnel Entry." The scope of the article (Sec. 370-1) was broadened accordingly. An industrial exception has been included to allow continued use of the National Electrical Safety Code (NESC) for those applications.

What happened: This new part of Art. 370 melds the requirements in Sec. 323 of the NESC with applicable requirements in the NEC. The result is relatively complete coverage of electric enclosures that function similarly to other enclosures within Art. 370, with the principal exception being that we work inside them. With the increasing deregulation of utilities and ever-changing distribution systems for electric energy, electric manholes and subsurface vaults are increasingly the domain of premises electrical systems and not the electric utilities. Please refer to our Engineer's book if you need more complete section-by-section coverage of this part of Art. 370.

Sec. 373-5(c) Ex. A new exception provides comprehensive rules for cable entries through a raceway extending into a cabinet.

What happened: Now you can use a nonflexible raceway sleeve between one-and-a-half and 10 ft long to entrain cables with entirely nonmetallic sheaths (including Type UF, but not Type MC cable with a nonmetallic jacket, for example) into the top only of a surface-mounted panel. The raceway must extend directly above the enclosure and not penetrate any structural ceiling. You need to plug the end with approved material (that is, acceptable to the inspector, which could be duct seal or even fiberglass insulation). You also need to secure raceway at its outer end, and the cables within 1 ft of that end. The jacket must be intact through the sleeve and into the enclosure at least a quarter inch. The same outer end needs a fitting to reduce the opportunity for abrasion, and the fill restrictions in Chapter 9 apply.

Background: This convoluted exception addresses a common practice in many areas of the country, and vehemently resisted in others. The usual application is a commercial establishment with block walls and a hung ceiling, where the general wiring method is Type NM cable. The idea is to put the panel on the wall, run a neat raceway sleeve through the suspended ceiling, and run the cables down. The only alternative in the prior Code was either to attach each cable to the panel individually and then box in the mess, or to nipple a wireway section above the ceiling and make the transition in that. The rules that finally emerged in this Code represent the compromise outcome of intense discussions extending over several cycles.

Sec. 380-9. Now you need to ground switch yokes whether or not the faceplate is metal. The only exception, generally recognizing a nonmetallic faceplate, is a very limited one for applications with no equipment ground available. Former Sec. 250-43(d) Ex. 2 and Sec. 430-144 Ex. 2, which used to allow lined covers for snap switches, have been deleted.

Background: The requirement reflects a simple reality, namely, that unqualified end users change out plastic plates for metal ones without permits or inspections, and the NEC has to anticipate that outcome.

EC&M tip: Don't confuse the grounding requirements for switch yokes with those for receptacles. All you need is the mounting screws in the case of metal boxes; you don't need "self-grounding" switch yokes, etc. Similarly, you don't need to remove the cardboard screw-retention washers. The self-grounding provisions of Sec. 250-146(b) [1996 NEC: 250-74 Exception No. 2] only apply to receptacles. Receptacles, while in use, are a link in the branch-circuit equipment grounding return path, and the yoke grounding connection is critical if it is being relied upon. This is not true for switches. Note also that dimmer switches are expressly included in the new requirements. The panel was aware of reports of an attempt to reclassify dimmer switches as other than snap switches, and wanted to be sure the requirement would continue to apply to dimmer switches.

Sec. 384-14. Power panelboard has been defined for the first time; and the lighting and appliance branch-circuit (LABC) panelboard was slightly redefined to accommodate some new protection rules.

Sec. 384-16(b). New rules for some smaller power panelboards enhance the protection required for them. If they are other than service equipment and have circuits of similar size to LABC panelboards, they will require individual protection as well.

What happened: First, the definitions: an LABC is, implicitly as before, one rated 30A or less and employing a neutral connection; and an LABC panelboard is one with more than 10% of its circuit positions connected to LABCs. If 10% or fewer of its circuit positions so qualify, then it is a power panelboard.

The individual protection rules for LABC panelboards haven't changed. What's new, however, is that for a power panelboard with more than 10% of its circuit positions rated 30A or less, it must have individual protection, unless it is part of service equipment. Please refer to our Engineer's book if you need more detailed information on this material and its history (which goes back about 65 years).

Sec. 400-8 Ex. The exception now defers to the provisions of Sec. 364-8 in defining the acceptable practice for attaching cords to a building surface.

Sec. 364-8 has very complete coverage of attaching cord drops from a busway to building surfaces, including the industrial exception that allows extensive use of cord or bus drop cables.

Sec. 410-11. This section has been revised to allow either two-wire or multiwire circuit conductors supplying a fixture to pass through its wiring compartment by right, without necessitating a separate listing for through wiring.

Although this is how the product standards have been judging the wiring compartments, many will find this modification counterintuitive. Identification for through wiring sounds like something that would apply to a branch circuit passing in and then out of the wiring compartment, whether or not the fixture is connected to it. Nevertheless, the testing laboratories have been making a contrary assumption for years, so there's really no reason not to make this change. The concept of "through wiring" in a form that requires listing recognition only applies to additional circuits that aren't part of either the fixture supply circuit or one of its companions in a multiwire circuit.

Sec. 410-15(b). Light poles used to route supply conductors within them are being used as a raceway, and must meet the appropriate rules, e.g. system separation in Chapter 7.

The prior wording never mentioned the magic word "raceway" as applicable to the actual inside of the pole, thereby leaving in doubt such provisions as Sec. 725-54(a)(1), which generally disallows Class 2 circuit conductors from being run in a power raceway. The drawing shows one way to meet that other requirement.

Sec. 410-56(g). Receptacles are now prohibited from being backfed through an energized attachment plug; use flanged inlets, etc. with male blades instead.

Background: This change should end a very common misapplication of attachment plugs and receptacles. When people try to arrange for standby portable generator supplies to buildings or structures, sewage lift stations, etc., they commonly use a receptacle as the receiving device. This guarantees the output on the standby generator will need to be through an attachment plug, which will have its blades energized while the generator is running, whether or not it is inserted into the receptacle.

Sec. 410-67(c). The minimum tap conductor length has been reduced from 4 ft to 18 in. On the literal text, however, the box still has to be at least 1 ft from the fixture.

The substantiation for this pointed to current recessed fixture designs that have tap conductors in the 18-in. range running from the fixture compartment to the prewired branch-circuit wiring compartment. Why should such taps have to observe a 4-ft minimum length, as required in the previous Code (and every preceding Code going back to 1940)? Meanwhile, the proposal didn't change the minimum box separation part of the requirement, namely 1 ft, although very few prewired fixtures have anywhere near that degree of separation. If they did, the minimum tap length would need to be at least 2 ft or longer.

EC&M tip: Ignore this entirely. This doesn't make sense. This section doesn't have anything to do with prewired fixtures suitable for normal branch-circuit wiring connections. The branch-circuit wiring compartment of a prewired fixture isn't an "outlet box" that has been "placed" (a field wiring requirement) as described in this rule. Due to evolving requirements for thermal protection, together with market forces, no fixtures to which this section applies are still in production.

Background: This change proves absolutely that we are so far from the original concept for this rule, even the panel no longer has any idea why it's in the Code. The rule dates from the 1940 NEC, and it has to do with establishing a cold lead so the fixture heat wouldn't reach the branch circuit conductors. Before the advent of thermal protection and prewired recessed fixtures, you ran a 4 ft to 6 ft lead in greenfield with Type AF or other high-temperature fixture wire from the lamp compartment to a box at least 1 ft away. The resulting loop of raceway made transmission of heat to the box impossible.

The beginning of the end came in the 1990 NEC, when Type AC or MC cable got added in, in spite of the fact that neither cable assembly had high-temperature conductors, and could not possibly be used for this purpose. Now, we describe a tap that isn't a tap covered by the Code to a box that isn't the box described in the Code. The panel should either find a use that corresponds to today's market and write a proper rule, or, more likely, delete it.

Art. 422. The article has been completely reorganized, with only very few of the old section numbers remaining the same.

Sec. 422-16(b)(1 and 2) [formerly Sec. 422-8(d)(1 and 2)]. Waste disposers, trash compactors, and dishwashers are only permitted to be field connected with a cord and plug where the manufacturer identifies a flexible cord as suitable for this application in the installation directions.

EC&M tip: This looks straightforward, but it isn't. In the case of disposers and compactors, the product standard requires the manufacturer to provide a cord connection kit and installation instructions, but only if the manufacturer chooses to allow for a cord connection. This may turn out to be a significant factor in the product selection decision, so be certain the owner of general contractor understands the issue.

In the case of dishwashers, there is a more significant problem, at least in the short term. The product standard is silent on cord connections, because the Code always addressed the question. As this is written, UL is preparing to add generic provisions in the guide card information on dishwashers allowing for the various flexible cords mentioned in the 1993 NEC (the last listing of specific types) as acceptable. That should prevent the effective removal of the long-standing allowance to cord-connect these appliances. UL expects this to stay in place for awhile, perhaps until the standard can be revised to add parallel requirements as those for compactors and disposers.

Note, however, the guide card revisions won't take effect until June of 1999. Until then, it will be a technical violation of this rule to cord-connect a dishwasher. By way of indicating this was unintended, a related change allows cords added in the field to measure the 4-ft maximum length to the rear plane of the appliance, just as OEMs have been able to do under the product standard.

Sec. 424-44(g). GFCI protection is now required for all electrically heated floor systems in bathrooms, hydromassage bathtub, spa, and hot tub locations, if the floor covering is conductive.

The word "conductive" in this context clearly means something more than metal or aluminum foil. Table 110-26(a) Condition 2 implicitly classifies tile and masonry as conductive in mandating they be considered as grounded surfaces. Therefore, although this is a judgment call, applying this rule to tile or other masonry floor seems appropriate. Note: This rule applies to an area, not a specific room. It also applies, for example, to a heated tile floor around a spa dropped into a corner of the master bedroom.

Sec. 430-6(a)(1) Ex. 3. For listed, motor-operated appliances with horsepower and full-load current ratings, now you can size circuit elements on the basis of the full-load current rating instead of taking the horsepower rating through the Art. 430 tables.

Background: Many appliances come with horsepower ratings that are patently absurd, intended to sell the product rather than conveying useful information. Sizing conductors based on these values rapidly results in extremely oversized conductors. This is a particular problem in applying Sec. 210-23(a).

Under the literal text of the prior wording, you had to take these "horsepower" ratings through tables at the end of Art. 430 to determine circuit protection and conductor sizing. This resulted in a perverse safety hazard because the circuit protection ends up larger than ever intended. It also created some absurd situations in the field. Garage door openers are often a classic example of the problem.

Consider a listed 5.3A garage door opener that says "1 peak horsepower" (Table 430-148: 16A). The literal text of the prior Code required a 20A individual circuit because of rules in this Article. Sec. 210-23(a) also forbids such loading on a lighting circuit. The listing assures the current draw on the nameplate is correct, and now we can rely on that to engineer the rest of the circuit.

Sec. 430-43. This section has been rewritten to clarify it only addresses an overload device that could restart a motor automatically after tripping due to overload.

This would include thermal protectors in motors that automatically reset when the motor cools down. Restarts after power failures, etc., are beyond the scope of this section, found in Part C of the Article, which covers motor and branch-circuit overload protection.

Sec. 430-52(c)(3) Ex. 1. The provisions of the exception allowing even higher trip settings for Design E motors than those allowed for other motors have been modified to include "Design B energy-efficient motors" on the same basis.

Some of the nuisance-tripping issues affecting Design E motors also affect these motors. There are, however, some other issues involving correlation that were never addressed. For example, Table 430-152 hasn't been correlated. Therefore, you can protect the design B motor from 0% to 800% by the table, and from 1100 % to 1700% by the exception, but not 800% to 1100%.

However, there is a far more substantive correlation issue. When the Design E allowance went into the 1996 NEC, it went with hefty derating requirements for controller sizing [Sec. 430-83(a)(1)], and disconnect sizing [Sec. 430-109(a)(1) and -109(f)]. The reason was the higher locked-rotor currents involved with Design E. The new Design B allowance in this section was motivated by the same concerns. Yet, the panel, without explanation, failed to correlate this new allowance in other parts of the article. This needs to be reviewed in the next cycle.

Sec. 430-102(a) Ex. 2. A disconnecting means for a group of coordinated controllers that drive several parts of a single machine or piece of apparatus (more descriptive wording than the old "multimotor continuous process machine") need no longer be mounted on the machine as long as it is in sight of the controllers. In addition, the controllers need no longer be adjacent to each other.

EC&M tip: Although this change allows for much greater flexibility in arranging equipment to control these large machines, be careful not to assume that because the controllers are visible from the machine, and the disconnect is also within sight, that the disconnect will be in sight of the controllers it disconnects. The drawing, on page 60, shows an example of where that would not be the case. This doesn't create a Code violation on the current literal text, but it does take this exception to places it has never been before.

Sec. 430-109(a)(6). A listed manual motor controller, additionally marked "Suitable as Motor Disconnect" and installed between the final branch-circuit ground-fault and short-circuit protective device and the motor, now qualifies as a motor disconnecting means. For a 2 hp or smaller stationary motor, operating at 300V or less, this device may be used at any point in the circuit as a disconnect; provided it has the requisite horsepower rating.

These devices don't have the spacings required by product standards for full-fledged disconnect switches, but they say "off" and "on." Moreover, they have been widely, and erroneously, assumed to have been usable as disconnecting means. The solution represented in these changes is to provide additional testing. For the sizes beyond those allowed for snap switches already, insist they only go in the circuit on the load side of the final branch-circuit and ground-fault protective device. You can use the smaller sizes (rated for stationary motors, 2 hp and 300V or less) the same as snap switches, except they are limited by their horsepower ratings instead of the 80% of full current restriction for snap switches.

Sec. 450-3 has been completely reorganized into two easy-to-use tables. This dramatically improves on what had been one of the most convoluted and confusing sections in the entire NEC.

Sec. 450-13(b). The allowance for 50kVA or smaller transformers to be placed in certain hollow spaces has been modified by dropping all reference to "fire-resistant" spaces. Instead, they must meet the separation-from-combustible-materials requirements in Sec. 450-21(a) and the ventilation requirements in Sec. 450-9.

Spaces don't have fire ratings; only partitions have those. Furthermore, even if you inferred the former rule applied whenever the space over the ceiling had walls and a ceiling qualifying as fire-resistant, the ceiling panels probably didn't. Therefore, true fire-resistant hollow spaces have been far and few between. The new wording is much more workable.

Sec. 455-6(b). The manufactured phase conductor supplied by a phase converter must be identified in all accessible locations with a distinctive marking.

The color or method isn't specified, although the proposal submitter suggested using the color yellow. This rule is important because Sec. 455-9 prohibits connecting single phase loads to the manufactured phase. You need to know which conductor to stay away from. Remember, Sec. 455-2 defines the manufactured phase as the conductor originating at the phase converter and having no solid connection to either of the single-phase input conductors.

Sec. 460-8(c)(1) Ex. A separate disconnecting means isn't required for a capacitor connected on the load side of a motor controller; this is liberalized from the prior restriction of being on the load side of the running overload device. This is useful because it allows omission of an independent disconnect for the capacitors, but at a point where they still aren't being connected to the load terminals of the controller. If the capacitors are connected at that point, the corrected power factor has to be accounted for in sizing the overload relays, per Sec. 460-9. Although technically well justified, that rule complicates the use of standard overload relay tables to the point of frequent misapplication.

EC&M tip: Don't confuse this issue with providing separate overcurrent protection for capacitors, under Sec. 460-8(b)(1). That protection remains a requirement unless you are on the load side of the actual running overload protection. There was a battle during the prior cycle, ultimately resolved on the floor of the Annual Meeting in favor of not changing that requirement.

Sec. 480-8(c). Working space per Sec. 110-26 and measured from the edge of the battery rack must now be provided about "battery systems."

EC&M tip: Some of these systems involve significant voltages, although individual cell voltages don't run much over 2V. This is a controversial change, because the telephone industry has more than 30 years experience with a 30-in. clearance rule. You may run into many industrial installations that used the same clearance, based on the same standard. If all voltages on a given rack don't exceed 60Vdc, then Sec. 110-26(a)(1) Ex. 2 gives the inspector, by special permission, the authority to reduce the clearances. You may need to explore this option, particularly if modifying an existing installation.

Art. 490. Equipment provisions of former Art. 710 have been relocated into Chapter 4 in this new article: "Equipment, Over 600 Volts, Nominal."

Sec. 490-35(b). The rule has been rewritten and its exception clarified as allowing instrument or control transformers and space heaters to be in high-voltage compartments of metal-enclosed power switchgear without additional access restrictions beyond those that apply to the high-voltage compartment generally.

This change clarified whether: 1) the intent of the rule was to allow access to space heaters and instrument transformers without going through interlocks even though they are in a high-voltage enclosure; or 2) the intent was simply to allow such equipment in the enclosure, but with interlocks and the isolating position still required for access because a high-voltage enclosure is involved. This has been unclear since the 1978 NEC, when these provisions originated. The answer is: Only the generally applicable access restrictions, such as the locked-door rule in Sec. 490-35(a), apply to this particular type of equipment.

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