NEC Ampacity Data Table (B)(2)(b) Ambient Temperature Correction Factors Based on 40 C (104 F)

Transcription

1 NEC Ampacity Data Table (B)(2)(b) Ambient Temperature Crection Facts Based on 40 C (104 F) F ambient temperatures other than 40 C (104 F), multiply the allowable ampacities specified in the ampacity tables by the appropriate crection fact shown below. Temperature Rating of Conduct Ambient Temperature ( C) 75 C 90 C 150 C 200 C 250 C Ambient Temperature ( F) 10 less less Table (B)(3)(a) Adjustment Facts f Me Than Three Current- Carrying Conducts in a Raceway Cable Number of Conducts Percent of Values in Table (B)(16) through Table (B)(19) as Adjusted f Ambient Temperature if Necessary and above 35 * Number of conducts is the total number of conducts in the raceway cable adjusted in accdance with (B)(5) and (6). Infmational Note No. 2: See (A) f adjustment facts f conducts in sheet

2 metal auxiliary gutters and (B) f adjustment facts f conducts in metal wireways. (1) Where conducts are installed in cable trays, the provisions of shall apply. (2) Adjustment facts shall not apply to conducts in raceways having a length not exceeding 600 mm (24 in.). (3) Adjustment facts shall not apply to underground conducts entering leaving an outdo trench if those conducts have physical protection in the fm of rigid metal conduit, intermediate metal conduit, rigid polyvinyl chlide conduit (PVC), reinfced thermosetting resin conduit (RTRC) having a length not exceeding 3.05 m (10 ft), and if the number of conducts does not exceed four. (4) Adjustment facts shall not apply to AC cable to MC cable under the following conditions: a. The cables do not have an overall outer jacket. b. Each cable has not me than three current-carrying conducts. c. The conducts are 12 copper. d. Not me than 20 current-carrying conducts are installed without maintaining spacing, are stacked, are suppted on bridle rings. (5) An adjustment fact of 60 percent shall be applied to AC cable MC cable under the following conditions: a. The cables do not have an overall outer jacket. b. The number of current carrying conducts exceeds 20. c. The cables are stacked bundled longer that 600 mm (24 in) without spacing being maintained. (b) Me Than One Conduit, Tube, Raceway. Spacing between conduits, tubing, raceways shall be maintained. (c) Circular Raceways Exposed to Sunlight on Rooftops. Where conducts cables are installed in circular raceways exposed to direct sunlight on above rooftops, the adjustments shown in Table (B)(3)(c) shall be added to the outdo temperature to determine the applicable ambient temperature f application of the crection facts in Table (B)(2)(a) Table (B)(2)(b). Infmational Note: One source f the average ambient temperatures in various locations is the ASHRAE Handbook Fundamentals. Table (B)(3)(c) Ambient Temperature Adjustment f Circular Raceways Exposed to Sunlight on Above Rooftops Distance Above Roof to Bottom of Conduit Temperature Temperature Adder C Adder F 0-13 mm (½ in.) Above 13 mm (½ in.) 90 mm (3½ in.) Above 90 mm (3½ in.) 300 mm (12 in.) Above 300 mm (12 in.) 900 mm (36 in.) Infmational Note to Table (B)(3)(c): The temperature adders in Table (B)(3)(c) are based on the results of averaging the ambient temperatures. (4) Bare Covered Conducts. Where bare covered conducts are installed with insulated conducts, the temperature rating of the bare covered conduct shall be equal to the lowest temperature rating of the insulated conducts f the purpose of determining ampacity. (5) Neutral Conduct. (a) A neutral conduct that carries only the unbalanced current from other conducts of the same circuit shall not be required to be counted when applying the provisions of (B)(3)(a). (b) In a 3-wire circuit consisting of two phase conducts and the neutral conduct of a 4-wire, 3-phase, wye-connected system, a common conduct carries approximately the same current as the line-to-neutral load currents of the other conducts and shall be counted when applying the provisions of (B)(3)(a). (c) On a 4-wire, 3-phase wye circuit where the maj ption of the load consists of nonlinear loads, harmonic currents are present in the neutral conduct; the neutral conduct shall therefe be considered a current-carrying conduct. (6) Grounding Bonding Conduct. A grounding bonding conduct shall not be counted when applying the provisions of (B)(3)(a). Table (B)(16) (fmerly Table ) Allowable Ampacities of Insulated Conducts Rated Up to and Including 2000 Volts, Through 90 C (140 F Through 194 F), Not Me Than Three Current-Carrying Conducts in Raceway, Cable, Earth (Directly Buried), Based on Ambient Temperature of 30 C (86 F)* Temperature Rating of Conduct s XHHW, USE, ZW s TBS, SA, SIS, FEP, FEPB, MI, RHH, RHW-2, THHN, THW- 2, THWN 2, USE-2, XHH, XHHW, XHHW-2, ZW-2 s XHHW, USE s TBS, SA, SIS, THHN, THW-2, THWN-2, RHH, RHW-2, USE- 2, XHH, XHHW, XHHW-2, ZW-2

3 Temperature Rating of Conduct COPPER ALUMINUM OR COPPER-CLAD ALUMINUM ** ** ** 10** ** / /0 2/ /0 3/ /0 4/ / *Refer to (B)(2) f the ampacity crection facts where the ambient temperature is other than 30 C (86 F). **Refer to 240.4(D) f conduct overcurrent protection limitations. Table (B)(17) (fmerly Table ) Allowable Ampacities of Single- Insulated Conducts Rated Up to and Including 2000 Volts in Free Air, Based on Ambient Temperature of 30 C (86 F)* Temperature Rating of Conduct s XHHW, ZW s TBS, SA, SIS, FEP, FEPB, MI, RHH, RHW-2, THHN, THW-2, THWN 2, USE-2, XHH, XHHW, XHHW-2, ZW-2 s XHHW s TBS, SA, SIS, THHN, THW-2, THWN-2, RHH, RHW-2, USE-2, XHH, XHHW, XHHW-2, ZW-2 COPPER ALUMINUM OR COPPER-CLAD ALUMINUM ** ** ** 10** ** / /0 2/ /0 3/ /0 4/ /

4 Temperature Rating of Conduct *Refer to (B)(2) f the ampacity crection facts where the ambient temperature is other than 30 C (86 F). **Refer to 240.4(D) f conduct overcurrent protection limitations. Table (B)(20) (fmerly Table ) Ampacities of Not Me Than Three Single Insulated Conducts, Rated Up to and Including 2000 Volts, Suppted on a Messenger, Based on Ambient Air Temperature of 40 C (104 F) Temperature Rating of Conduct XHHW, ZW s MI, THHN, THW-2, THWN-2, RHH, RHW-2, USE-2, XHHW, XHHW-2, ZW-2 XHHW s THHN, RHH, XHHW, RHW-2, XHHW-2, THW-2, THWN-2, USE- 2, ZW-2 COPPER ALUMINUM OR COPPER-CLAD ALUMINUM / /0 2/ /0 3/ /0 4/ / *Refer to (B)(2) f the ampacity crection facts where the ambient Table (B)(21) (fmerly Table ) Ampacities of Bare Covered Conducts in Free Air, Based on 40 C (104 F) Ambient, 80 C (176 F) Total Conduct Temperature, 610 mm/sec (2 ft/sec) Wind Velocity Copper Conducts AAC Aluminum Conducts Bare Covered Bare Covered

5 Copper Conducts AAC Aluminum Conducts / / / / / / / / / / / / / / / / Table (C)(4) Ambient Temperature Crection Facts F ambient temperatures other than 40 C (104 F), multiply the allowable ampacities specified in the ampacity tables by the appropriate fact shown below. Temperature Rating of Conduct Ambient Temperature ( C) 90 C Ambient Temperature ( F) 10 less less

6 Table (C)(67) Ampacities of Insulated Single Copper Conduct Cables Triplexed in Air Based on Conduct Temperatures of and (221 F) and Ambient Air Temperature of 40 C (104 F)* Temperature Rating of Conduct [See Table (C).] Volts Ampacity ,000 Volts Ampacity Conduct ( ) MV-90 (221 F) MV-90 (221 F) / / / / *Refer to (C)(4) f the ampacity crection facts where the ambient air Table (C)(68) Ampacities of Insulated Single Aluminum Conduct Cables Triplexed in Air Based on Conduct Temperatures of and (221 F) and Ambient Air Temperature of 40 C (104 F)* Temperature Rating of Conduct [See Table (C).] Volts Ampacity ,000 Volts Ampacity Conduct ( ) MV-90 (221 F) MV-90 (221 F) / / / / *Refer to (C)(4) f the ampacity crection facts where the ambient air Table (C)(69) Ampacities of Insulated Single Copper Conduct Isolated in Air Based on Conduct Temperatures of and (221 F) and

7 Ambient Air Temperature of 40 C (104 F)* Temperature Rating of Conduct [See Table (C).] Volts Ampacity ,000 Volts Ampacity 15,001-35,000 Volts Ampacity Conduct ( ) 90 C (194 F) MV-90 (221 F) 90 C (194 F) MV-90 (221 F) 90 C (194 F) MV-90 (221 F) / / / / *Refer to (C)(4) f the ampacity crection facts where the ambient air