Wiring Systems NEC

2013.05.28 18:58
Wiring Systems NEC

 

 

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NEC (National Electrical Code) 에 준하는  위험지역에서의 연결방식에 대한 개요를 살펴봅니다.

 

Cable systems and accessories should be installed in positions that prevent them from being subject to mechanical damage, corrosion, chemical attack, heat and other detrimental environmental conditions. Selection of the wiring system and cable type must consider these influences and where exposure to such conditions are avoidable, protective measures such as minimising the risk of mechanical damage by the use of appropriate armoured cable types should be considered. The connection of cables and conduits to the electrical apparatus must be in accordance with the requirements of the relevant type of protection and installation rules.

 

National Electrical Code (NEC) Zone Wiring Methods

In Class I, Division 1 locations, the NEC permits the following wiring methods:

 

● Type MC cable, listed for use, with a gas / vapor tight continuous corrugated aluminum sheath, an overall jacket of suitable polymeric material, separate grounding conductors, in accordance with Sections 250- 122 and 501.10 of the NEC, and provided with termination fittings listed for the application, e.g. Hawke type 711 cable gland/connector.

● Type ITC cable, listed for use with a gas / vapor tight continuous aluminum sheath, an overall jacket of suitable polymeric material in accordance with Section 501.10 of the NEC and provided with termination fittings listed for the application, e.g. Hawke type 711 cable gland/connector.

●  Threaded rigid metal conduit, threaded steel intermediate metal conduit, or type MI cable with termination fittings approved for the location and in accordance with Section 501.10 of the NEC.

 

 

 

All boxes, fittings and joints must be explosion-proof.

 

In Class I, Division 2 locations, the NEC permits the following wiring methods:

 

● Type MC, MV, ITC, PLTC, TC or MI cable with approved termination fittings in accordance with Section 501.10 of the NEC.

 

● Threaded rigid metal conduit, threaded steel intermediate metal conduit.

 

● Non-incendive field wiring using any of the methods suitable for wiring in ordinary locations in accordance with Section 501.10 of the NEC.

 

Boxes, fittings and joints need not be explosion-proof except as required by the NEC code.

 

Cable Seals, Class 1, Division 1

Cables must be sealed at the termination. The sealing fitting, e.g. a barrier type cable gland, must provide a seal against the passage of gas or vapours through the fitting. Type MC cables with multi-conductors, a gas / vapour tight continuous corrugated aluminum sheath and an overall jacket with a suitable polymeric material must be sealed with an appropriate fitting, e.g. Hawke type 711, after removing the cables jacket and all other coverings so that the sealing compound surrounds each individual insulated conductor. Cables with twisted pairs and shielded cables require the removal of the shielded material or separation of the twisted pairs unless the fitting, e.g. cable gland, is an approved means which minimises the entrance of gases or vapours and prevents propagation of flame into the cable core. If the fitting complies with this requirement, there will be information provided in the fittings installation instructions detailing the means to achieve the seal. Additional testing may be required on the fitting and the style and type of cable to show compliance with the sealing requirements.

 

An NRTL approved cable sealing fitting e.g. barrier type cable gland, must be fitted onto cables where they enter explosion-proof enclosures.

 

 Further guidance is given in Section 501-5(d) of the NEC.

 

 

Cable Seals, Class 1, Division 2

Cables must be sealed at the point of entrance into enclosures that require to be approved for Class I locations. A sealing fitting must comply with the above criteria given in "Cable Seals, Class I, Division 1".

 

An NRTL approved cable sealing fitting e.g. barrier type cable gland, must be fitted onto cables that enter explosion-proof enclosures.

 

United States Coast Guard - Wiring Methods

Electrical installations in hazardous (classified) locations must comply with the general requirements of Section 43 of the IEEE standard 45 and either the NEC Articles 500 - 505 or IEC 60079 series publications.

 

In hazardous (classified) locations, the USCG 46 CFR Sub-Chapter J, permits the following wiring methods:

 

● Marine shipboard cables that are permitted for use, must meet all the requirements of either IEEE standard 45, IEC 60092-3 and the applicable flammability requirements. Cables constructed to IEC 60092-3 must meet with the flammability requirements of IEC 60332-3, Category A.

 

● Metal-clad (type MC) cables that are permitted for use, must have a continuous corrugated gas tight, vapour-tight, and water-tight sheath of aluminum or other suitable metal that is close fitting around the conductors and with fillers. The MC cable must have an overall jacket of an impervious PVC or thermoset material and be certified or listed to UL 1569.

 

For information on other wiring methods permitted and further information, refer to Subpart 111-60 of the USCG 46 CFR.

 

Each cable entry into explosion-protected equipment must be made with an appropriate fitting or cable gland that maintains the integrity of the equipment.

 

Cables with multi-conductors that enter explosion-proof enclosures, must be sealed with an appropriate fitting, e.g. barrier type cable gland, after removing the cables jacket and all other coverings so that the sealing compound surrounds each individual insulated conductor. Cables with twisted pairs and shielded cables require the removal of the shielded material or separation of the twisted pairs unless the fitting, e.g. barrier type cable gland, is an approved means which minimises the entrance of gases or vapours and prevents propagation of flame into the cable core. If the fitting complies with this requirement, there will be information provided in the fittings installation instructions detailing the means to achieve the seal. Additional testing may be required on the fitting, and the style and type of cable to show compliance with the sealing requirements.

 

The equipment grounding path should be carefully considered when using Shipboard Cables or type TC cables, as these may not inherently provide a grounding means. The armour of Shipboard Cables should be grounded but can not be used as the grounding conductor. An appropriate sized grounding conductor should be included in each cable.

 

American Petroleum Institute - Wiring Methods

Class 1, Division 1

The API RP 14F Recommended Practice for the design and installation of electrical systems for fixed and floating offshore petroleum facilities recommends the following wiring methods for hazardous (classified) locations:

 

● Type MC-HL metal clad cables as defined in UL 2225.

 

● Armoured marine shipboard cable with an overall impervious sheath over the armour, constructed in accordance with UL 1309, and listed as "Shipboard Cable Marine" by a National Recognised Testing Laboratory (NRTL). This wiring method is a departure from the NEC.

 

● Type ITC cable that is NRTL - listed for use in Class I, Division 1 locations with a gas / vapor tight continuous corrugated aluminum sheath and with an overall PVC or other suitable polymeric jacket.

 

● Threaded rigid copper-free aluminum conduit.

 

● Threaded rigid steel, hot dipped galvanized conduit, coated with PVC, or other suitable material, and with the interior protected by an additional means.

 

An NRTL approved cable sealing fitting, e.g. barrier type cable gland complying with UL 2225, must be fitted onto cables where they enter explosion-proof enclosures.

 

For further information and other wiring methods acceptable for Division 1, refer to Clause 6.4.2.2 of the API RP 14F.

 

For fitting requirements of cables with multi-conductors, twisted pairs or shielded conductors into explosion proof equipment. See clause 12.4.1.

 

Class 1, Division 2

● Wiring methods as recommended for use in Division 1.

 

● Type MC cable with a gas / vapour tight continuous corrugated aluminum sheath, an overall PVC or other suitable polymeric jacket, and grounding conductors in accordance with NEC 250-122.

 

● Non-armoured marine shipboard cable, with an overall impervious jacket in accordance with UL 1309 and listed as "Shipboard Cable Marine" by a NRTL. This wiring method is a departure from the NEC.

 

 

Additional wiring methods acceptable for Division 2 include type PLTC, ITC, TC and MV cables. It is recommended that an overall PVC or other suitable polymeric material jacket is included for these cable types.

 

For additional information, refer to Clause 6.4.2.3 of API RP 14F.

 

In Division I locations, all electrical equipment (except intrinsically safe systems and equipment inside purged enclosures) should be explosion-proof.

 

In Division 2 locations, the equipment does not need to be explosion-proof, except where necessary to maintain the integrity of the installation.

Further information on the use of equipment is given in Clause 6.4.7 of API RP 14F.

 

An NRTL approved cable sealing fitting, e.g. barrier type cable gland complying with UL 2225, must be fitted onto cables where they enter explosion-proof enclosures.

 

For fitting requirements of cables with multi-conductors, twisted pairs or shielded conductors into explosion proof equipment. See clause 12.4.1.

 

Class 1, Zones 0, 1 and 2

The API RP 14FZ, Recommended Practice for the design and installation of electrical systems for fixed and floating offshore petroleum facilities for unclassified and Class I, Zone 0, Zone 1 and Zone 2 locations, recommends the following wiring methods for hazardous (classified) locations.

 

Class 1, Zone 1

● Type MC-HL metal clad cables as defined in UL 2225.

 

● Armoured marine shipboard cable with an overall impervious sheath over the armour, constructed in accordance with UL 1309, and listed as "Shipboard Cable Marine" by a National Recognised Testing Laboratory (NRTL). This wiring method is a departure from the NEC.

 

● Type ITC cable that is NRTL - listed for use in Class 1, Division 1 locations with a gas / vapour tight continuous corrugated aluminum sheath and with an overall PVC or other suitable polymeric jacket.

 

● Threaded rigid copper-free aluminum conduit.

 

● Threaded rigid steel, hot dipped galvanized conduit, coated with PVC, or other suitable material, and with the interior protected by an additional means.

 

 

Non-armoured marine shipboard cable, with an overall impervious jacket in accordance with UL 1309 and listed as "Shipboard Cable Marine" by a NRTL. This wiring method is a departure from the NEC.

 

 

For further information and other wiring methods acceptable for Zone 1, refer to Clause 6.4.2.2 of the API RP 14FZ.

 

For fitting requirements of cables with multi-conductors, twisted pairs or shielded conductors into explosion proof equipment. See clause 12.4.1.

 

Class 1, Zone 2

 

● Wiring methods as recommended for use in Zone 1.

 

● Type MC cable with a gas / vapor tight continuous corrugated aluminum sheath, an overall PVC or other suitable polymeric jacket, and grounding conductors in accordance with NEC 250-122.

 

● Non-armoured marine shipboard cable, with an overall impervious jacket in accordance with UL 1309 and listed as "Shipboard Cable Marine" by a NRTL. This wiring method is a departure from the NEC.

 

Additional wiring methods acceptable for Zone 2 include type PLTC, ITC, TC and MV cables. It is recommended that an overall PVC or other suitable polymeric material jacket is included for these cable types.

 

For additional information, refer to Clause 6.4.2.3of API RP 14FZ.

 

Further information on the use of equipment is given in Clause 6.4.7 of API RP 14FZ.

 

An NRTL approved cable sealing fitting, e.g. barrier type cable gland complying with UL 2225, must be fitted onto cables where they enter explosion-proof enclosures.

 

For fitting requirements of cables with multi-conductors, twisted pairs or shielded conductors into explosion proof equipment. See clause 12.4.1.

 

Where cables enter equipment which is permitted for use in Zone 2 or unclassified areas and that is not explosion-proof, a suitable cable fitting e.g. cable gland design, need not be explosion-proof, except when necessary to maintain the integrity of the enclosure and as required by the Recommended Practice.

 

In unclassified and Zone 2 locations, when the metallic sheath is approved as a grounding conductor, the continuous metal sheath of the MC cable or the combined metallic sheath and grounding conductors may be used as the grounding conductor when used with termination fittings that are NRTL-listed to UL 514B.

 

National Electrical Code (NEC) Zone Equipment Marking

Equipment that is listed for use in Class I, Zones as permitted by the NEC, should be marked as follows:

 

● Class I, Zone 0 or Class I, Zone 1 or Class I, Zone 2 and

 

● Applicable gas classification group(s).

 

● Temperature classification.

 

Example:

 

 

 

 

National Electrical Code (NEC) Division Equipment Marking

Equipment that is approved for use in Class I, Class II or Class III, Division 1 or 2 as permitted by the NEC, may be marked as follows:

 

● Class I or Class II or Class III or a combination of where appropriate.

 

● Division 1 or Division 2 equipment not marked to indicate a Division or marked Division 1 is suitable for both Division 1 and 2 locations as defined in the NEC.

 

● Group classification.

 

● Operating temperature or temperature range or as permitted by the NEC.

 

North American Ingress Protection

Non-Hazardous Locations

 

North American Ingress Protection

Hazardous Locations 

 

 

Further information can be found in NEMA Standard Publication 250 and UL 50 Standard Publication.

 

The enclosures are designed to protect and to provide additional protection as stated below:

 

 

 

 

 

 

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