NEC 2008 - UPDATE

Article 100 Please review definitions for:

Bonding, Branch-Circuit Over-current Protection, Clothes Closet
Ground, Grounding, Grounded, Intersystem Bonding
Termination, Kitchen (Key words “an area”), Neutral
Conductor/Neutral Point, Short Circuit Current Ratings

Article 110.16 Revised: Electrical equipment shall be field marked with
“Arc Flash Warning” signs.

Article 110.22 Revised and New: All equipment shall be marked
(B) + (C) “series combination systems” and identified, whether manufactured
as a system or an individually engineered designed systems.

Article 110.26 Revised: Equipment rooms require 2 egress doors when
(C)(2) equipment is rated 1200 amps or more and is over 6 feet wide.

Article 110.26(C)(3) New: Egress Doors in equipment rooms less than 25’
from equipment rated 1200 amp or more require panic/pressure
hardware and the doors are required to open in the direction of the
egress (see 110.33 (A)(B) for over 600V equipment)

Article 200.2 (B) Revised: Continuity of the grounded conductor cannot
rely on metallic enclosures, raceways, or cable armor.

Article 210.4 (B) Revised: All ungrounded conductors of a multi-wire circuit
shall be simultaneously disconnected at the point of origin.

Article 210.4 (D) Revised: All ungrounded and neutral conductors of a multi-wire circuit shall be
grouped together when entering in a panel unless in their own raceway or cable.
(Example of grouping is wire tires).

Article 210.8 Deleted: GFCI Protection is now required for all 120 V 15 and 20
(A)(2) + (A)(5) amp receptacles in garages, accessory building and unfinished basements.
(Exceptions were deleted for appliances, etc.)

Article 210.8 Revised Definition: In other than dwellings, all 15 amp and 20 amp 120V
(B) (2) receptacles require GFCI Protection in kitchens other than dwellings.
(definition of a kitchen)

Article 210.8 Revised Definition: In other than dwellings, all 120 V 15 and 20
(B) (4) amp outdoor receptacles are required GFCI Protection

Article 210.8 New: All 15 amp and 20 amp 120 V receptacles require GFCI
(B) (5) Protection within 6’ of sinks in other than dwellings (see specific exceptions).

Article 210.8 (C) Revised Definition: All receptacles not exceeding 240 V required GFCI Protection
in a dwelling boat hoist.

Article 210.12 (B) Revised Definition: Major change for arc fault protection in dwelling units. All
120V, 15 amp and 20 amp branch circuits. (See specific list of rooms)

Article 210.52 Revised Definition: Switched controlled receptacles are not considered as the
required outlets for dwelling units. (switching one half of the receptacle will still
meet the required outlets).

Article 210.52 (E) New: Balconies, decks and porches that are accessible from inside a dwelling unit
(20 ft 2) or more, require at least 1 receptacle outlet not more than 6 ½’ above the
surface.

Article 210.60 (A) Revised: Sleeping rooms in dormitories shall have the required receptacle outlets
in accordance with 210.52 (A) and (D).

Article 210.62 Revised: Show window receptacles shall be within (18 inches) of the top of the
window.

Article 215.6 Revised: Feeders shall include an equipment grounding conductor
(see 250.32 (B) ) for exceptions for existing buildings.

Article 215.10 Revised: Ground fault protection of equipment when supplied by a
EXCEP. 2 transformer must be on the load side of the transformer and not the primary side
when required by this article.

Article 230.44 Revised: Service conductors when installed in cable trays with
EXCEP. fused wiring requires solid barriers and the cable tray must be identified “service
entrance conductors” in a manner along the entire length of the tray so to be
readily traced.

Article 230.82 (3) Revised: Disconnects ahead of metering equipment is being considered as a
mandatory installation by many power companies, especially on 277/480V
services. This will provide a level of safety for working on metering equipment. In
most cases it appears the disconnect will be owned, installed and maintained by
the power companies. (Check with your local power company for clarification).

Article 230.205 (A) Revised: Service disconnects for primary power shall be permitted to not be
readily accessible.

Article 240.24 (F) New: Prohibits over current devices to be installed over stair steps.

Article 250.30 Revised: Where grounding multiple separately derived systems
(A)(4) to a single grounding electrode conductor, the bonding jumpers must be installed
at the point the grounding taps are connected.

Article 250.32 (B) Revised: An equipment grounding conductor is required to be ran with the feeder
when feeding separate buildings or structures. (See exception)

Article 250.35 Revised: Clarifies generator bonding, grounding and grounded
(A)(B) conductor sizing for separately derived and non separately derived systems (See
250.30 for separately derived); (See 250.102 (C)) for supply side of non
separately derived systems and 250.102 (D) for load side of non separately
derived systems) (Example of a separately derived system is : when the grounded
conductor of the system is broken and not solid by a transfer switch)

Article 250.52 Revised: Concrete encased electrodes can be located vertically
(A)(3) when within the portion of the footer or foundation connected to earth (See other
requirements of this article)

Article 250.64 (D) Revised: Clarifies grounding requirements when services consist of multiple
disconnects (1) tapping a single grounding electrode conductors sized for the
total service and each tap size for the individual disconnect by 250.66.
(2) Installing individual grounding electrode conductors sized for each individual
disconnect by 250.66. (3) Installing a single grounded electrode conductor to a
common location, in an enclosure.

Article 250.94 Revised: Bonding for other systems such as CATV, communications, etc. shall
have an external means available by installation of listed equipment grounding
bars that will accept at least 3 terminations. These bars shall be bonded with a
minimum #6 AWG copper conductor to the service equipment or the grounding
electrode. (See exceptions for existing installations).

Article 250.104 Revised: Clarifies when metallic water systems are metallically isolated at a
tenant space supplied by a feeder, the equipment grounding conductor ran to an
accessible metallic water system is size by 250.122 for the purpose of bonding
the tenant space sub panel.

Article 250.122 (C) Revised: Clarifies that a single equipment grounding conductor used in
raceways, cables and cable trays for multiple circuits shall be sized for the largest
over-current device by 250.122. (See 392 for other grounding requirements and
sizing for cable trays.)

Article 250.146 (A) Revised: Clarifies that surface mounted box covers may be listed for grounding
when a receptacle is mounted to the cover by a permanent means or locking
screws with flat type surface cover mounting holes (key words listed for
grounding)

Article 300.4 (E) New: Cables and raceways installed under metal corrugated roof decking shall
not be less then 1 ½” from the surface.

Article 300.5(B) Revised: Clarifies that the interior in all raceways and enclosures underground
are wet locations. (This includes PVC and conductors and splices installed shall
be rated for wet locations.) (See 300.9 for above grade wet locations)

Article 300.5 Revised: Clarifies underground conductors and cable under
(C) + (C1) a building shall be in a raceway.

Article 300.5 Revised: Clarifies direct buried cables and conductors emerging
(D) (1) from grade shall be protected to at least 8’ above finish grade to at least 18”
below grade

Article 300.9 New: Insulated conductors in raceways, in wet locations above grade, shall be
listed for wet locations. (Example: NMB installed in PVC outside to feed an a/c
disconnect would be a violation) (Damp locations would also apply to this
requirement when condensation and moisture occur).

Article 300.12 New: Cables and conduits when installed in open bottom type
(EXCP 2) equipment are not required to be mechanically secured to the enclosures.
(Bonding of metal raceways and cables is a required)

Article 310.15 New: Conductors and cables installed in raceways exposed to
(B) (2) (C) direct sunlight on roofs will follow the adjustments shown in Table 310.15 (B) (2)
for ambient temperatures. (Please take note.)

Article 314.16 Revised: Devices or utilization equipment wider than a single
(B) (4) box shall have a double volume allowanced for each gang required by Table
314.16 (a). (Example given: is an electric dryer outlet in a single gang box will not
allow proper box fill space for the conductors and device)

Article 314.28 Revised: Clarifies that this article is to include boxes with
(A)(2) splices as well as Angle and U pulls, to be sized by this article.

Article 334.12 Revised: NM cable is not permitted in Type I and Type 2
(EXCEP.) construction; (basically block and steel construction types). It is now permissible
if installed in a raceway, not a partial sleeve, and meets all other installation
codes. (Interior installation of S.E. and S.E.R. cables also apply to Part II of this
Article. Also see 338.10(B)(4).)

Article 334.12 Revised: Clarifies NM shall not be installed in a wet and damp
(B)(4) location. (Keep in mind, NM installed in PVC or Metallic raceways does not
change the location classification.)

Article 334.15 (C) Revised: When sleeving NM on the wall in a basement or crawl space thru
conduit or tubing, the cable must be secured within 12” of where it enters the
tubing or conduit. Insulated bushing or adapters are also a requirement for
abrasion. (See this entire article for other requirements)

Article 334.80 Revised: Clarifies that the ampacity of NM cable shall be adjusted by 310.15
(B)(2)(a) if affected when installed in contact with thermal insulation without
maintaining cable spacing. (See the manufactures test reports for effects)

Article 338.12 (A) Revised: Clarifies S.E. cable shall not be used underground with or without a
raceway (See 338.12 (A)&(B) for article restructure).

Article 342.30 (C) New: IMC not over 18” does not require support when installed without
coupling and is terminated without encountering oversized, concentric or
eccentric knockouts. (Same rule applies for RMC., see344.30 (C) and PVC,
352.30 (C).)

Article 348.12 (1 Revised: FMC shall not be permitted in wet locations.

Article 348.60 Revised: Clarifies FMC where installed for flexibility requires the installation of an
equipment grounding conductor. (See 350.60, the same requirement applies for
LFMC)

Article 350.30 (A) Revised: Revised and restructured for securing LFMC when fished or installed for
flexibility. (See article, goes by trade sizes)

Article 352.10 (F) Revised: Revised and new F.P.N. added to clarify that schedule 80 is identified
for areas subject to physical damage.

Article 362.30 New: ENT shall be permitted to be fished in unbroken lengths
(EXCEP 3) without couplins.

Article 366.2 Revised: Revised definitions for metallic and non-metallic gutters. Distinguishes
that gutters and wireways are not the same. (See articles 376 and 378 for
wireways.)

Article 376.56 Revised: Clarifies that distribution blocks that serve live parts in a
(B) (4) wireway shall be of the insulated type. (Wireway covers do not provide
compliance.)

Article 404.8 (C) New: General use multiple snap switches that are supplied by more than 1 circuit
must be listed and marked as a 2 or 3 circuit switch, or rated for the system line to
line voltage.

Article 406.4 (G) New: Receptacles when grouped or ganged in a enclosure with other devices
must be arranged so the voltage between all adjacent devices does not exceed
300V unless an approved and identified barrier is installed between the devices
(Now mirrors existing snap switch requirements in 404.8 (B).

Article 406.8 Revised: Standard non-locking straight blade receptacles rated 15 and 20 A;
(A) (B) & (Excep.) 125V and 250V installed outdoors in a damp location or in any wet location shall
be a listed weather resistant type. Exception: high pressure spray areas shall be
permitted to have weather proof enclosures that remain weather proof after the
attachment plug is removed.

Article 406.11 New: Tamper-Resistant Receptacles are now required in all locations in dwelling
units listed in 210-52 (This will also apply to retrofits and repairs)

Article 408.3 (F) New: Switchboards and panel boards supplied by 4 wire delta high leg system,
must be permanently field marked to warn users of voltage supply. (See specific
wording as to how to mark the system. Example of a high leg system voltage is
120/240v 3 phase with a high leg of 208v.)

Article 408.4 Revised: Panel board circuit directories have been required to be specifically
labeled to identify what each circuit breaker feeds, now spare breaker spaces with
a breaker installed shall also be identified as a spare position. (Both rules apply to
service/panel changes as well as new installations.)

Article 408.36 Revised: Panel boards require over-current protection on the supply side (See
exceptions 1, 2, and 3). The differentiation between a lighting and appliance
panel board and a power panel board has been removed. The limitation of 42
overcurrent devices in a panel board has been revised to be permitted unless
prohibited by the panel boards “listing” or by exception 2. (My interpretation is that
transformers and feeders in the 10’ tap rule will also require a main.)

Article 409 Revised: Industrial Control Panels: This article should be reviewed in its entirety
especially 409.106 and 409.110 for “listing” information that is required to be
marked on equipment.

Article 410.16 Revised: LED luminaries were included in the article requirements for clothes
(A) (3) closets (must be listed for the use)

Article 410.130 Revised: Listed internal or external disconnects are required for
(G1, 2, 3) indoor, other then residential fluorescent luminaries, that utilize double ended
lamps and contain ballast for servicing. If supplied by a multi-wire branch circuit
then all conductors including the grounded conductor shall be disconnected. A
single switch is permissible to disconnect more than one fixture when the switch is
accessible, within sight of the fixture, the fixtures are not supplied by a mulitwire
circuit and the area will not be left in total darkness. (This will apply to old and new
installations).

Article 422.51 Revised: Clarifies the GFCI protection requirements for vending machines
manufactured or remanufactured prior to January 1, 2005.

Article 422.52 New: Electric drinking fountains now require GFCI protection.

Article 424.19 Revised: Disconnecting means for fixed electric space heating equipment shall
have an ampere rating not less than 125% of the total load of the motors and
heaters. Disconnect locking devices shall remain in place whether or not the lock
is installed.

Article 430.103 Revised: Motor and controller disconnecting means are not permitted to be a
type that will close automatically. (Example given is a time clock). While manually
switched off, could automatically return to the on position while servicing the unit.

Article 440.14 Revised: A/C and refrigeration disconnects shall not be mounted on equipment
access panels or to obstruct the visibility of the equipment nameplate. Disconnect
locking devices shall remain in place with or without the lock installed.

Article 445.19 Revised: Generator disconnects shall be lockable in the open position.
(Important: Article 225.32 and 445.18 also apply to the disconnect location of a
generator.)

Article 480.5 New: On over 30V storage battery systems a disconnecting means shall be
readily accessible and within sight from the system; in order to disconnect the
derived ungrounded conductors.

Article 501.30(B) Revised: Flexible and liquid tight metal conduit shall not be used as the sole
grounding means path (also see 502.30 (B) and 503.30 (B) for same requirement)

Article 511.20 New: Definitions added to define a major and minor repair garage (see article for
all revisions.) (May require an engineer evaluation for a minor repair
classification.)

Article 525.11 Revised: Where multiple sources of supply serve portable structures in carnivals,
etc. and are not separated by less than 12’, the equipment grounding conductors
must be bonded together by 250.122 but not smaller than 6 awg. (see new
definitions added in this article)

Article 547.5 (F) Revised: Agricultural Buildings: Equipment grounding conductors shall be copper
and if installed underground it shall be insulated or covered.

Article 547.5 (G) Revised: Accessible receptacles supplying dedicated loads are not required
GFCI protection when a GFCI receptacle is installed within 3 feet, of the non-
GFCI receptacle.

Article 547.9 (E) New: When more than 1 service is installed less than 500’ apart, a plaque shall
be installed at the distribution points donating the locations of the other
distribution points.

Article 555.9 Revised: Conductor splicing devices listed for submersion on floating piers can
be used above the water line and below the datum plane in junction boxes.

Article 555.21 Revised: Class I, Division I & II areas; total revision (should be read)

Article 600.6 Revised: When sign and controller disconnects are not within sight
(A) (1) of the sign, a disconnect locking means that is the type remains in
place shall be permitted.

Article 600.21 (E) Revised: Attic and soffits that ballast, transformers and power
supplies are installed, require a light containing a switch or a wall
switch at the point of entry. The light shall be located at the
equipment.

Article 680.12 Revised: Clarifies maintenance disconnects must be readily accessible and 5’
from the inside walls of a pool, spa, or hot tub unless separated by a barrier
that provides a 5’ reach path (integral hot tub disconnect are not
recognized)

Article 680.22 Revised: Several articles for receptacle distances have been
changed to be located at least 6’ from the inside walls of a pool.
See 680.22 (A)(1), (2),(3) ; 680.34,680.43 (A), 680.43 (A)(1), 680.62
(E), 680.71.

Article 680.22 (B) Revised: Hard wired and cord connected pool pumps are required
to be GFCI protected. Applies to 15A and 20A, 120V or 240V.

Article 680.22 (E) Revised: Receptacle outlets not associated with a indoor pool shall
be at least 10’ from the inside walls of the pool.

Article 680.26 Revised: Equipotenial bonding requirements have had a major
revision. Please review in its entirety: short cut to some of the
changes are as follow:

1. All surfaces paved and unpaved are now included in the 3’ equipotential
plane distance.

Types of Grids
A. Structural reinforcement steel includes conductive type rebar and wire
mesh when used in concrete are recognized as that portion of the grid.
B. A single 8AWG bare solid copper conductor following the
contour of the pool. This conductor shall be installed 18” to
24” from the inside walls of the pool and at a minimum depth
of 4” and maximum depth of 6” below subgrade.
C. Copper grid construction in 12” by 12” network.

Note: (1) Conductive Rebar and wire mesh are only acceptable when
used only in a concrete pour. (2) Outside of a poured area an 8 AWG
copper conductor or grid network as described in B will only be acceptable.
(3) Deck bond shall be connected to the pool in 4 uniformed spaced
locations.

Article 680.26 (C) New: An intentional bond of a minimum conductive surface area of 5806 mm2
(9 in.2) shall be installed in contact with the pool water and it must be connected
to the equipotential bonding grid. (This would apply to pool water that is not in
contact with a (9 in2) conductive surface.)

Article 680.31 Revised: Storable Pool pumps are required to have integral GFCI
protection built into the supply cord within 12” of the attachment plug.

Article 680.71 Revised: Hydromassage tubs and their associated equipment are required to be
on an individual branch circuit.

Article 680.74 Revised: Clarifies that other metal piping for a hydromassage tub
shall not be required to be attached to any panel boards or
electrodes but connected to a terminal on the circulating pump.

Article 695.6 Revised: Fire pump supply conductors when protected by fire rated assemblies
or listed electrical protective circuit systems shall now have a 2 hr rating or be
encased in concrete.

HOLDING TO ELECTRICAL SPECIFICATIONS

Engineers should maintain their positions on electrical system design, whether for code issues, good design practice- or the owner’s best interest

"Why on earth did you design it that way?"

This is a plaint often heard from the contractor, construction manager, or owner when documents are issued for construction. More often than not, the statement is liberally littered with modifying expletives.

The engineer so challenged, must first decide if the question has a legitimate basis. If so, is it a National Electrical Code (NEC) requirement, good practice, or merely designer preference?

The key is to examine code requirements, how the engineer can maintain a position, and the potential impacts to both the engineer and the project if they fold on their position.

Engineers are charged with a mandate to "safeguard life, health and property, and promote the public welfare," as well as meet project requirements. In addition, there are instances in which they are called upon to certify that drawings to which they have affixed their seals meet all requirements of the NEC and the Authority Having Jurisdiction (AHJ). To meet these weighty obligations engineers must consider seriously their mandate and- on a more practical level- interpret applicable NEC sections for each project and assure that their design meets all requirements.

By stamping and signing design drawings, engineers are signifying that they believe the documents meet project and code. When these documents are sent to contractors for construction bidding, the questions begin. The most common topics of discussion- from contractors, owners and others, comprise the following:

Wire Sizing

• Ampacity. There have been numerous articles written on the subject of conductor sizing to meet the NEC requirements as described in Article 310 (see sidebar, "NEC Conductor Sizing,") These articles agree

The Cast of Characters

Like it or not, there are differing viewpoints on a construction project, and as long as we live in a free market society,there always will be. Participants each have their own agendas and issues of paramount importance. A description of the
cast of character every engineer encounters (and often embodies) follows. While these stereotypes are certainly unfair to many, at the same time there is an underlying truth to the generalizations.

The Owner. The owner wants the best project for either the lowest first cost or life-cycle cost. Meeting code is not always a top priority, particularly when code requirements conflict with project requirements-and when the cost of
compliance increases the budget.

The Construction Manager. Typically hired by the owner, the CM’s views, for the most part, parallel those to the owner.

The AHJ. The Authority Having Jurisdiction (AHJ) wants to project that is safe and meets their interpretation of the various codes. They are usually not interested at all in whether their interpretations impact the cost of the project.

The Contractor. The builder wants to complete the project and make a profit; they’re not necessarily interested in whether the project meets Code, but only that it passes inspection. Also, the contractor be interested in changes to the
design after the contract is signed that mean greater profit for the contractor. So, all opportunities to reduce cost or find design errors can increase the contractor’s profit margin-and his influence with the owner.

The engineer must consider all of these viewpoints, and make value judgments in light of code, cost, constructability, safety and consumer satisfaction (as well as their own profit picture). They must advise the owner on the future operation of the project. Any changes proposed by the contractor must be beneficial to the owner.

That a number of issues must be addressed to properly size conductors, including ambient temperature, termination temperature, number of current-carrying conductors in a raceway, character of the load and type of conductor insulation. While
now included in NEC Appendix B- which is not a code mandate- the Neher-Macgrath calculations for sizing of conductors installed in underground duct banks should also be considered to properly size conductors in a partially insulated environment.

The diligent engineer applies each requirement in the appropriate manner and arrives at a conductor size suitable for the load, the environment and the overcurrent protection. Yet, the controversy often begins when a member of the
construction team compares the conductor sizes on the contract documents to the uncorrected, 75°C column in table 310-16 in the NEC and concludes that the engineer has sized the conductors incorrectly.

The owner or contractor then takes the position that the conductors are too large and, to economize, suggests that the sizes be reduced to match the referenced column.

• Voltage Drop. Ampacities are just one factor in proper conductor sizing. Just as important, though often neglected, is voltage drop. NEC Articles 210-19 (a) (FPN No. 4) and 215-2(b) (FPN No.2)- which are not mandatory rules-recommend sizing both feeders and branch circuits to prevent a voltage drop exceeding 3 percent at the farthest outlet, where the maximum total voltage drop of the feeders and branch circuits does not exceed 5 percent

When the feeder and branch circuit conductors for long circuits are sized on this basis, the conductor sizes are increased even more than that required for ampacity. Perhaps because it is not mandatory, contractors and owners sometimes forget this basic fact. It should not be overlooked, however, because performance and the operating life of utilization equipment can be adversely affected.

Electrical Working Clearance

Clearance for electrical equipment are specified in NEC Articles 110-16 and 384. Working clearances are based on voltage level and conditions of installation, and for installations below 600 volts, these clearances range from 3 to 4 feet in front and in back of equipment (where the equipment has rear access). Headroom is also given as a minimum of 6.5 feet to prevent the installation of electrical equipment in crawlspaces.

Article 384 covers dedicated space in the vicinity of electrical equipment for the installation of conduit and limited physical protection of equipment. Generally speaking, this space is equal to the footprint of the equipment extending from the floor on which the equipment is mounted to the next structural floor, or 25 feet, whichever is less. The article also restricts the intrusion of pipes and ducts into this space.

While the passage clearly states that no equipment foreign to the electrical installation shall be installed in the zones, this often becomes a point of contention between engineer and contractor. In the contractor’s view, the shortest distance between two points is a straight line, even if that line is a pipe passing directly over electrical equipment.

While the code seems clear and straightforward, this is a frequent problem at the construction site. Clearance requirements are often violated to the extent that equipment doors cannot be opened, and Owners and even AHJs may prefer to look the
other way. Many engineering firms have specific coordination stipulations, both in drawings and specifications, to prevent space conflicts between mechanical and electrical systems. In the field, however, there must be a commitment to implement them,

Transformer Protection

Transformer overload and short-circuit protection are addressed in Article 450 of the NEC. Depending on voltage levels and conditions of maintenance and supervision, one of two protection schemes can be used: either primary overcurrent protection
only, or primary and secondary overcurrent protection. Also, the NEC permits fairly wide latitude in the sizing of overcurrent devices.

As a matter of good practice, however, better protection will be realized with breaker settings or fuse ratings lower than the maximum allowable. Likewise, primary-only protection is a minimum-only requirement, which – unlike primary and secondary
protection- does not provide the best protection under all types of fault conditions. Plus, it may introduce nuisance tripping due to magnetizing inrush, cold load pickup and emergency operating conditions.

Using primary and secondary protection, with the primary breaker set between 175 and 200 percent, there is less opportunity for nuisance tripping while offering adequate short-circuit protection for both primary conductors and the transformer. The
secondary overcurrent device, set at 125 percent of full load, provides overload protection. In addition, the primary overcurrent device should be examined to ensure that the transformer damage curve (defined by ANSI/IEEE C57.109) is fully
protected by the primary device, while allowing the transformer magnetizing inrush point to fall below trip characteristics. That way, energizing the transformer will not cause a nuisance trip.

Unfortunately, contractors routinely question the use of larger overcurrent devices and primary conductors on the primary side of the transformer.

Engineers are accused of "overdesigning" projects, overlooking cost savings from reduced conductor and overurrent device sizing. Yet, in most instances, the larger overcurrent device is the same frame size; so, for example, reducing the trip
size from a 200-ampere to a 125-ampere trip on a breaker results in no savings at all. The difference in cost between the conductors and conduit that is perhaps 4 feet long is negligible. In reality, the time wasted in asking the question is
probably more valuable than the cost of the materials needed for the more reliable, better protected installation.

Grounding/Earthing

Conflicts on grounding most often occur between the engineer and the owner’s equipment suppliers. The NEC is very clear. In Article 250-54, it spells out the standard for connecting all grounding conductors to a single grounding electrode.

When electronic systems are installed in a facility, the equipment installation technicians typically request an isolated ground not connected to any other ground in the building, often stating that their equipment will not work without the isolated ground.
The conflict between the NEC requirement and the supplier’s desire is easily resolved: Connect the ground for the electronic system as close to the grounding electrode as possible; this meets the NEC requirement and gives electronic systems their solid, earth ground connection.

The real issue for the systems is having a minimum voltage above ground on the signal ground for the system. By connecting the system ground close to the grounding electrode, there is minimum impedance between the system ground and earth ground,
reducing the voltage to a low value, no matter what the ground current.

An associated but less common request from system technicians is that the voltage difference between neutral and ground at the utilization equipment be less than 1 volt. The equipment ground installed as noted above will minimize the voltage on the
ground; reducing voltage level on the neutral at the utilization equipment is more problematic. Utilization equipment often has a switching power supply, which generates significant harmonic currents that are impressed on to the neutral of the system with a resultant increase in neutral current.

As Ohm’s Law states, when current is increased through the constant circuit impedance, voltage increases. Therefore, the neutral has an inherent voltage impressed at the utilization equipment terminals well above the requirement outside of 1 volt over ground. In fact, no equipment manufacturer has been able to demonstrate either:
1) Good reason for maintaining the neutral-to-ground voltage less than 1 volt; or
2) Any equipment malfunctions attributed to this voltage difference.

Fault Duty

Fault duty on distribution equipment should be a focal point of the engineer’s concentration. Not only is it critical to safety and reliability, but it is an NEC-mandated issue in Article 110-9, which says that equipment intended to break current at fault levels shall have an interrupting rating sufficient for the current that is available at the line terminals.

Contractors, Owners and Construction Managers often seem to think that fault duty of electrical equipment is a myth propagated by engineers to increase the costs of projects. Yet, the fact is that the engineer must meet the NEC requirement by either designing a fully rated system or, as permitted by Underwriters Laboratories (UL), designing a series-rated system. NEC enforces UL requirements in Article 110-3(b), which says that listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

The Contractor that has some passing knowledge of fault duty will suggest that the distribution system be series rated in place of a fully rated system. This suggestion becomes difficult when the series connected rating is applied to systems with a mixture of multiple manufacturers or with various overcurrent devices that are not listed as series connected by UL.

As UL plainly states, "These ratings are applicable only when the series connected devices have been investigated by UL in combination with the end-use equipment and the equipment in which these devices are used is marked with the series connected
rating." Therefore, if series connected devices are not listed in UL Recognized Component directory, they are not suitable for series-rated application.

Between the NEC and UL requirements, engineers very carefully must meet the specific requirements for series ratings confirming in shop drawings equipment labeled for that specific rating- or maintain that all systems must be full-rated.

Resolving Codes and Costs

With all of these viewpoints clouding the issues, the engineer has a difficult problem. Because the engineering firm is hired by the owner, either directly or indirectly, their first commitment must be to the client- the owner.

Along with this commitment, however, engineers must also meet the mandate to protect public safety and welfare. This becomes one of the most sensitive issues engineers face, especially when they choose to hold to a design or specification
against the owner’s wishes. When this happens, these options are available to engineers:

• A Simple Approach: Show the owner where the code does not allow a proposed change. In most cases this is enough

• A Cost-Based Approach: Connect the code-mandated design with construction cost savings or operational savings,

• A Diplomatic Approach: Develop an alternative solution meeting the owner’s requirements and code requirements.

Sometimes, this implies more design time and additional construction cost, but it may be the path of least resistance when owners are adamant about a change.

If these approaches don’t work, further options become less pleasant. Where there appears to be no major hazards, engineers may comply with the owner’s desires and go on record with a letter to the owner stating the engineer’s objection to the approach and recording the reasons why.

For more critical issues, engineers can send a letter absolving themselves of any responsibility- and simply not incorporate the requested approach into the contract documents. This position may risk the loss of future work with the same owner, but this may be a better option than violating a public mandate to design safe buildings.

NEC Conductor Sizing

There are four criteria used for conductor sizing to meet the NEC requirements:

1) The overcurrent device must be sized for the sum of the non-continuous load plus 125 percent of the continuous load.
The overcurrent device may be rounded up to the next available standard size, as long as the device does not exceed 800 amperes.

2) The conductor must be sized so that termination temperatures do not exceed 60°C for conductors smaller than 100 amperes or #1 American wire gauge (AWG), and 75°C for conductors larger than 100 amperes or #1/0 AWG. This results in using the 60°C column of 310-16 for all conductor sizing of circuits 100 amperes and smaller, and the 75°C column of 310-16 for conductors larger than 100 amperes. Even if insulations are utilized, such as XHHW, Z, TFE, etc. two columns must be used to determine conductor sizes.

3) Conductor size and insulation type must take into consideration conditions of use to prevent insulation damage. Conditions of use include more than three current-carrying conductors in a single raceway and high-temperature ambients. High temperature ambients are-according to the heading of the correction-factor chart for 310-16-any ambient conditions that exceed 30°C or 86°F Most electrical rooms and mechanical rooms and mechanical rooms where mechanical rooms where electrical equipment is installed will exceed 86°F under typical operating conditions

Wire sizing and conductor sizing must not only meet code requirements, they must also meet special needs, such as those for partially insulated environments.

4.) The overcurrent device must protect the conductor under all conditions of use.

PRICE AND COST ANALYSIS

Some form of price or cost analysis should be performed in connection with every procurement action, regardless of whether the organization is a vendor or a subrecipient. The form and degree of analysis, however, are dependent on the particular subcontract or purchase, and the pricing situation. Determination of price
reasonableness through price or cost analysis is required even though the procurement
is source directed by the contracting officer of the sponsoring agency.

In some purchases, price analysis alone will be sufficient; in others, price analysis will be used to corroborate the conclusions arrived at through cost analysis. The form and degree of analysis are dependent on facts surrounding a particular subcontracting or purchasing situation. The scope of price analysis performed and the particular techniques used will depend on whether or not cost analysis is done, as well as on such factors as type of product or service, dollar value, purchase method, and extent of competition.
The words "vendor" and "subcontractor" used herein are interchangeable.

Price Analysis is the process of deciding if the asking price for a product or service is fair and reasonable, without examining the specific cost and profit calculations the manufacturer and/or supplier used in arriving at the price. It is basically a process of comparing the price with known indicators of reasonableness.

When adequate price competition does not exist, some other form of analysis is
required. Some reasons that could affect adequate price competition are: specifications are not definitive, tolerances are restrictive, or production capacity limits those eligible to bid.

Examples of other forms of price analysis information include:

• analysis of previous prices paid
• comparison of vendor's price with the in-house estimate
• comparison of quotations or published price lists from multiple vendors

Cost Analysis is the element -by-element examination of the estimated or actual cost of contract performance to determine the probable cost to the vendor. The goal is to form an opinion on whether the proposed costs are in line with what reasonably economical and efficient performance should cost.

Cost or pricing data, which should be provided by the subcontractor, are the means for conducting cost analysis. Such data provide factual information about the costs that the subcontractor says may be incurred in performing the contract. Cost analysis should be performed in those situations where price analysis does not yield a fair and reasonable price and where cost data are required in accordance with prime contract clauses.

Cost analysis techniques are used to break down a contractor's cost or pricing data so as to verify and evaluate each component. Some of the cost elements examined for
necessity and reasonableness are materials costs, labor costs, equipment and overhead. These costs can be compared with actual costs previously incurred for similar work, the cost or pricing data received from other manufacturer and/or supplier, and independent cost estimate breakdowns.