This article is about Low Voltage NEC / SASO / IEC Unjacketed Wire Material Selection Criteria & Requirements of Electrical Power System as per International Codes and standards for Commercial Buildings, Plants and Refinery Projects.
Low Voltage NEC / SASO / IEC Unjacketed Wire Material Selection Criteria
- For the purposes of this standard SAES-P-104 (Wiring methods and Materials), severe corrosive environments include:
a) Outdoor offshore locations, and
b) Outdoor onshore locations within one kilometer from the shoreline of the Arabian Gulf; all of the Ras Tanura Refinery and Terminal; and within three kilometers from the shoreline of the Red Sea. c) Location where chlorine or other corrosive chemicals are being handled d) Battery rooms”
Locations where chloride or other corrosive chemicals are being handled are also corrosive environments. In these locations, enclosures, conduit, fittings and wiring must be resistant to the chemicals present. - Outdoor locations correspond to wet or damp locations, and indoor locations correspond to dry locations as defined by National Electrical Code Article 100.
Commentary Note 4.4: A structure enclosed by walls on three sides only, and having a roof, is considered an outdoor location. A non-air-conditioned building is considered an indoor location. A shop that has its doors kept open to facilitate entry of vehicles is considered an indoor location. - Low voltage unjacketed insulated wires shall comply with NEC, SASO 55 or IEC 60227.
Exception to Sections 5.2.1 and 5.2.2: - For wiring of equipment such as lighting fixtures, etc., that require higher temperature wires and cables, the above minimum temperature ratings shall be increased accordingly.”
- NEC low voltage wires shall be rated 600 V, shall have a minimum temperature rating of 90°C dry / 75°C wet, and shall conform to UL standards according to the particular type (e.g., UL 83 for THHN/THWN and UL 44 for XHHW).
- Low voltage unjacketed insulated wires, except when used as grounding conductors, shall not be used in cable trays (unless listed and marked for use in cable trays), duct banks involving manholes, or direct burial applications.
Commentary Notes: 5.2.1.1 and 5.2.2.1 - A certificate from the manufacturer that the cable has been type tested by a third party testing agency acceptable to the Coordinator, CSD/ESD, and that it meets applicable UL standards is acceptable in lieu of formal UL listing or certification.”
- Power and control conductors shall be stranded copper, except solid copper conductors 6 mm sq. (10 AWG) and smaller may be used in non-industrial locations. Stranded power, control and grounding conductors shall have stranding in accordance with IEC 60228 Class 2, except flexible cords, portable cables, battery leads and motor leads may have finer stranding in accordance with appropriate UL Standards or the manufacturer’s recommendations.
- Minimum size of conductors shall meet the requirements of Table 1.
- (A) Dry Locations. Insulated conductors and cables used in dry locations shall be any of the types identified in NEC 2008 Code.
NFPA 70, NEC 310.8 (A)”
(B) Dry and Damp Locations. Insulated conductors and cables used in dry and damp locations shall be Types FEP, FEPB, MTW, PFA, RHH, RHW, RHW-2, SA, THHN, THW, THW-2, THHW, THHW-2, THWN, THWN-2, TW, XHH, XHHW, XHHW-2, Z, or ZW. NFPA 70, NEC 310.8 (B)
(C) Wet Locations. Insulated wires used in wet locations shall be
(1) Moisture-impervious metal-sheathed;
(2) Types MTW, RHW, RHW-2, TW, THW, THW-2, THHW, THHW-2, THWN, THWN-2, XHHW, XHHW-2, ZW; or
(3) Of a type listed for use in wet locations. NFPA 70, NEC 310.8 (C)
(D) Locations Exposed to Direct Sunlight – Insulated conductors and cables used where exposed to direct rays of the sun shall be of a type listed for sunlight resistance or listed and marked “sunlight resistant. NFPA 70, NEC 310.8 (D) - Corrosive conditions – Conductors exposed to oils, greases, vapors, gases, fumes, liquids, or other substances having a deleterious effect on the conductor or insulation shall be of a type suitable for the application. NFPA 70, NEC 310.9
- No conductor shall be used in such a manner that its operating temperature exceeds that designated for the type of insulated conductor involved. In no case shall conductors be associated together in such a way with respect to type of circuit, the wiring method employed, or the number of conductors that the limiting temperature of any conductor is exceeded. NFPA 70, NEC 310.10
- All wires shall be marked to indicate the following information, using the applicable method described in 310.11(B):
(1) The maximum rated voltage.
(2) The proper type letter or letters for the type of wire or cable as specified elsewhere in this Code.
(3) The manufacturer’s name, trademark, or other distinctive marking by which the organization responsible for the product can be readily identified.
(4) The AWG size or circular mil area. (5) Cable assemblies where the neutral conductyor is smaller than the ungrounded conductors shall be so marked. NFPA 70, NEC 310.11 (A) - “Surface Marking.
The conductors and cables shall be durably marked on the surface. The AWG size or circular mil area shall be repeated at intervals not to exceeding 610 mm (24 in). All other markings shall be repeated at intervals not exceeding 1.0 m (40 in).
NFPA 70, NEC 310.11 (B) (1)” - Optional Markings.
All conductors and cables contained in Chapter 3 shall be permitted to be surface marked to indicate special characteristics of the cable materials. These markings include, but are not limited to, markings for limited smoke, sunlight resistant, and so forth.
NFPA 70, NEC 310.11(D)” - Conductor Constructions and Applications.
Insulated conductors shall comply with the applicable provisions of Table 310.13 (A). (See attachment)
These conductors shall be permitted for use in any of the wiring methods recognized in Chapter 3 and as specified in their respective tables.
NFPA 70, NEC 310.13″ - Types, THHN,THWN, TWN75 AND T90, shall have a jacket of Nylon extruded tightly over the insulation. UL 83, 4.3.1″
- Single conductor outer covering shall be in accordance with Section 6.1 Typically XHHW. UL 44, 6.1.3.2
- Low voltage unjacketed insulated wires shall comply with NEC, SASO 55 or IEC 60227.
Exception to Sections 5.2.1 and 5.2.2: - For wiring of equipment such as lighting fixtures, etc., that require higher temperature wires and cables, the above minimum temperature ratings shall be increased accordingly.”
- SASO 55 or IEC 60227 type low voltage wires shall be rated 450/750 V, shall have a minimum rating of 85°C, and shall meet the flame test of IEC 60332-1.
- Markings may be by printing or by reproduction in relief on or in the insulation or sheath. IEC 60227-1, Sec. 3.
- Stranded Conductors shall be in accordance with IEC-60228, Class 2 for Stranded Conductors. IEC 60227-3, 2.3.1.
- Insulation shall be PVC applied around the conductor, thickness shall comply with Column 3 Table 1, Resistance shall comply with Column 5 Table 1.
IEC 60227-3, 2.3.2.
International Standard and Codes for Low Voltage UL/NEC
- Non-Hazardous Indoor Enclosures, Installation and Pre-Commissioning
- Boxes, Enclosures, and Accessories Materials Selection & Requirements
- 3. SAES-P-104 Wiring Methods and Materials, 13 January 2008
4. UL 44 Thermoset-Insulated Wires and Cables, November 2005
5. UL 83 Thermoplastic Insulated Wires and Cables, April 2006
6. IEC 60227-1 PVC Insulated Cables of Rated Voltages up to and including 450/750V, (General Requirement), October 2007
7. IEC 60227-3 PVC Cables of Rated Voltages up to and including 450/750V, (Non-sheathed Cables), January 2002
8. NFPA 70 National Electrical Code (NEC), 2008 Edition
1. NEC 2008 Table 310.13(A) Conductor Application and Insulations
