Wiring systems and enclosures

Typical FNICO is shown in Fig. X/3.5.2-2B. The major components are FNICO power supply, field cable, and field cable termination devices. Power supply connections to the host control system are made at its safe area terminals, and those to the field tmnk at its hazardous area terminals. It also includes the necessary functions for a reliable fieldbus with those of an energy-limited interface. This incorporates a repeater function, connections for 24 VDC supply input, and a switchable terminator [30], Field terminators take the form of a DIN rail-mounted terminal module. In an FNICO system, the requirements are simple the wiring hub and its enclosure must be certified for zone 2 or division 2 as appropriate, and be suitable for the environment. 

Do all interior wiring systems include provisions for grounding metal parts of electrical raceways, equipment, and enclosures ... 

Explosion-proof enclosures are characterized by strong metal enclosures with special close-fitting access covers and breathers that contain an ignition to the inside of the enclosure. Field wiring in the hazardous environment is enclosed in a metal conduit of the mineral-insulated-cable type. All conduit and cable connections or cable terminations are threaded and explosion-proof. Conduit seals are put into the conduit or cable system at locations defined by the National Electric Code (Article 501) to prevent gas and vapor leakage and to prevent flames from passing from one part of the conduit system to the other. 

Although transformers suitable for other industrial installations are generally suitable for producing applications, certain options may be desirable— primarily due to environmental considerations. At locations subject to harsh environmental conditions, and particularly at locations subject to washdown with high-pressure hoses, non-ventilated enclosures are desirable, if not necessary. Likewise, at locations subjected to salt water and salt-laden air, it often is desirable to specify copper windings and lead wires. Most manufacturers provide standard units with aluminum windings and lead wires. Even if aluminum coils are used, it is almost always desirable to require stranded copper lead wires. This will lessen corrosion and loose terminal problems when transformers arc interconnected to the facility electrical system with copper conductors. If the transformers are to be installed outdoors in corrosive environments, cases should be of corrosion-resistant material (e.g., stainless steel) or be provided with an exterior coating suitable for the location. 

The uses and end points measured for enclosure studies are similar to mesocosms, but here a portion of the natural environment is enclosed and manipulated, rather than constructing an artificial system. Manipulations include adding previously unexposed organisms to an enclosure in a contaminated environment, or applying test chemicals to an enclosed portion of a noncontaminated environment. Terrestrial enclosures are usually corrals fenced in by wire or plastic mesh or impermeable barriers such as metal or plastic sheets. They may range from < 1 m to more than a hectare. Aquatic enclosures may include a section of the shoreline fenced off by plastic curtains (littoral enclosures) or boxes made of flexible plastic sheets suspended in open water (limno-corrals). Small enclosures are used to monitor acute toxicity or sublethal effects, while larger enclosures may study population, community, or ecosystem level end points. 

Typically, an oxy/fuel combustion equipment system is considered to be a Class 1, Division 2, Group D electrical installation per NFPA 70 (articles 500, 501, and 502). Note that the Group is defined as a function of the flammable fuel being handled. See NFPA 497A for help in determining the classification of a particular oxy/fuel combustion application. All components, enclosures, conduits, and wires must be suited for the particular classification of the oxy/fuel equipment system electrical installation. 

Answer This is the reference rail for the entire system. So in fact, all on-board dc-dc converters present in the system usually need to have their respective (power) grounds tied firmly to this system ground. The system ground in turn usually connects to the metal enclosure, and from there on to the earth (safety) ground (i.e. into the mains wiring). 

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