NEC Consultant

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NEC Consultant

United States
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Holt M.,NEC Consultant
EC and M: Electrical Construction and Maintenance | Year: 2010

Wiring method requirements including information on sizing and securing and supporting raceways and other parts of electrical systems are provided in Article 300. Article 300.11(A) defines that indenpendent support wires that are secured at both ends are allowed to be added for the support of wiring methods. 300.17 says that raceways must be large enough to permit the installation and removal of conductors without damaging them and to allow the dissipation of the heat generated by current flowing through the conductors. To protect conductors from abrasion during installation, raceways must be mechanically complete between the pulling points before the conductors are installed [300.18(A)]. Circuits and equipment should be installed in a way that does not substantially increase the potential spread of fire [300.21]. Devices or equipment must directly act upon or sense the air in a duct or plenum that primarily serves to transport environmental air [300.22(B)].


McPartland B.J.,NEC Consultant
EC and M: Electrical Construction and Maintenance | Year: 2010

Identification of electric code violations is defined through two examples. The first violation shows the lack of work space as defined by 110.26. Part (A)(1), which says that sufficient access and working space shall be provided and maintained about all electrical equipment to permit ready and safe operation and maintenance of such equipment. Another concern in this example is the white-colored conductor terminated under a circuit breaker terminal, which is a violation of 200.6(A) or 240.22. The second violation is the case of an outdoor lighting fixture with an integral occupancy sensor, which violates rule of 410.10(A), 'Wet and Damp Locations'. It says that fixtures installed in the bathtub and shower area must be listed for either damp or wet locations, depending on whether the fixture is subjected to the direct spray of the shower head or not.


Holt M.,NEC Consultant
EC and M: Electrical Construction and Maintenance | Year: 2010

Mike Holt, NEC Consultant, shares his views on the application of the requirements in Article 690 of the National Electrical Code (NEC) for photovoltaic systems. Section 690.15 of the article states that the disconnecting means for all sources need to be grouped and identified when the equipment is energized from more than one source, such as an inverter. Section 90.16(A) states that it is to provide a means to disconnect a fuse from all sources of supply when energized from both directions. The fuse needs to be capable of being disconnected independently of fuses in other PV source circuits. Disconnects for fuses need to be installed for PV output circuits where fuses that must be serviced are unable to be isolated from energized circuits. The disconnect needs to be within sight of and accessible to the fuse, externally operable without exposing the operator to contact with live parts, and plainly indicating whether in the open or closed position.


The advantages and disadvantages of each raceway should be known before making a final selection. Intermediate metal conduit (IMC) is a circular metal raceway with an outside diameter equal to that of rigid metal conduit (RMC). The wall thickness of IMC is less than that of RMC, so it has more interior room for conductors. A revision to 342.30(C) in the 2008 Code required support for any length of raceway that's coupled or terminates in a ringed knockout. RMC, commonly called rigid, has long been the standard raceway for providing protection from physical impact and from difficult environments. Flexible metal conduit (FMC), commonly called Greenfield or flex, is a raceway of an interlocked spiral metal strip. Although the length of an FMC installation is not limited, it's primarily used for the final 6 ft or less of raceways between a more rigid raceway system and equipment that moves, shakes, or vibrates. The NEC requires equipment to have an equipment grounding conductor (EGC).


Holt M.,NEC Consultant
EC and M: Electrical Construction and Maintenance | Year: 2011

The revised edition of the 2011 NEC involves a new definition for a common term, bonding jumper, supply-side. A supply side bonding jumper is a conductor on the supply side or within a service or separately derived system to ensure the electrical conductivity between metal parts required to be electrically connected. The revised reference to bonding and grounding electrode conductors provides a much more specific Code application. The description of currents that aren't considered to be objectionable has been changed in 250.6(C). Temporary currents from abnormal conditions, such as ground faults, aren't to be classified as objectionable current. The removal from the Art 100 of the term, grounding conductor also had an effect in 250.8(A), which makes it clear that its conductor termination requirements apply to bonding jumpers, equipment grounding conductors, and grounding electrode conductors. The 2011 NEC addresses the location of ground detection sensing equipment for ungrounded systems and adding marking requirements for ungrounded systems.


Holt M.,NEC Consultant
EC and M: Electrical Construction and Maintenance | Year: 2011

The changes made to the 2011 NEC have significant impact on supplying power to a structure and protecting the conductors carrying that power. A new exception in 230.24 permits lower clearances for overhead service conductors. The new standard states that the normal 8-ft clearance needs to be only 3 ft if the voltage between conductors does not exceed 300V and the roof area is guarded or isolated. The physical protection requirements for underground service conductors (230.32) now include structures instead of just buildings. The language of Part IV, Sec. 230.40 now makes better use of defined terms and addresses multiple accessory structures in an effective manner. The NEC has long permitted installers to connect fire pump equipment upstream of the service equipment and this permission also applies to standby power systems. Article 240 provides the requirements for selecting and installing overcurrent protection devices (OCPD). The overcurrent exists when current exceeds the rating of equipment or the ampacity of a conductor.


Holt M.,NEC Consultant
EC and M: Electrical Construction and Maintenance | Year: 2011

Article 110, by NEC, providing many general guidelines that govern electrical installations, is discussed. Art. 110.10 states that electrical equipment must have a short circuit current rating (SCCR) that permits the circuit protective device to open from a short circuit or ground fault without extensive damage. 110.11 states that installers must give consideration to the presence of corrosive gases, fumes, vapors, liquids, or other substances that can have a deteriorating effect on the conductors or equipment. 110.14 highlights that the use of only conductor terminal devices and splicing devices specifically identified for the conductor material and follow the recommended installation procedures. 110.24 states that a new section requires some equipment to be marked with the available fault current and requires updating of that marking if modifications of the electrical system occur. 110.9 and 110.10 states that all equipment must have an interrupting rating or SCCR that is at least equal to the available fault current.


Tedesco J.,NEC Consultant
EC and M: Electrical Construction and Maintenance | Year: 2011

Two examples of failed electric connections that do not comply with the National Electrical Code (NEC) and present serious safety questions are discussed. The first example if that of energized multiconductor cable assemblies supplying kitchen equipment in a mess hall and which are not protected from physical damage, nor is the raceway completely installed. Short sections of raceways used to contain conductors or cable assemblies for protection from physical damage shall not be required to be installed complete between outlet, junction, or splicing points. The second example is that of a electrical improvisation rears its ugly head identified near a sump pump that had stopped working. As permitted in 300.5(E), a box or conduit body shall not be required for splices and taps in direct-buried conductors and cables. It is recommended that listed boxes and handhole enclosures shall be permitted where covered by gravel, light aggregate, or noncohesive granulated soil if their location is effectively identified and accessible for excavation.


Holt M.,NEC Consultant
EC and M: Electrical Construction and Maintenance | Year: 2011

Some of the steps that need to be considered while installing a branch circuit are discussed. For personnel safety, each multiwire branch circuit must have a means to simultaneously disconnect all ungrounded conductors at its origin. The ungrounded and neutral conductors of a multiwire branch circuit must be grouped together using cable ties or similar means at the point of origination. Insulated equipment grounding conductors size 6 AWG and smaller must have a continuous outer finish either green or green with one or more yellow stripes. If two or more branch circuits supply devices on the same yoke, a means must be provided at the circuits point of origin to disconnect simultaneously all ungrounded conductors that supply those devices. Install GFCI at a readily accessible location for all 15A and 20A, 125V receptacles in any of the following commercial/industrial locations such as bathrooms, kitchens, rooftops, outdoors, sinks, indoor wet locations, locker rooms with associated showering facilities, and garages.

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