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Standards - Note 3

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WIRE AMPACITIES, INSULATORS, AND IMPEDANCES


Below are some useful tables pertaining to ampacities, insulators, and impedances of various wires.

These are derived from the 2017 Philippine Electrical Code [ or the 2017 National Electrical Code ], but are rearranged in a manner that is easier to interpret and understand.

1.) Allowable Ampacities of Insulated Conductors in Raceway.

The areas, ampacities, and insulation types of the following tables are based on 2017 PEC Table 3.10.2.6(B)(16) [ or 2017 NEC Table 310.15(B)(16) ].

1.1.) Copper Wire Ampacities
---------------------------------------
|  Copper  |  Insulation Max Op. Temp |
---------------------------------------
|   Area   | 60degC | 75degC | 90degC |
|   mm^2   |  Amps  |  Amps  |  Amps  |
---------------------------------------
|    2.0   |    15  |    20  |    25  |
|    3.5   |    20  |    25  |    30  |
|    5.5   |    30  |    35  |    40  |
|    8.0   |    40  |    50  |    55  |
|   14.0   |    55  |    65  |    75  |
|   22.0   |    70  |    85  |    95  |
|   30.0   |    85  |   100  |   115  |
|   38.0   |   100  |   115  |   130  |
|   50.0   |   115  |   140  |   150  |
|   60.0   |   130  |   155  |   170  |
|   80.0   |   155  |   190  |   205  |
|  100.0   |   185  |   220  |   240  |
|  125.0   |   210  |   255  |   285  |
|  150.0   |   240  |   285  |   320  |
|  175.0   |   260  |   305  |   345  |
|  200.0   |   275  |   325  |   360  |
|  250.0   |   315  |   375  |   425  |
|  325.0   |   370  |   435  |   490  |
|  375.0   |   395  |   470  |   530  |
|  400.0   |   400  |   480  |   535  |
|  500.0   |   445  |   530  |   595  |
---------------------------------------

1.2.)  Copper Wire Insulators
----------------------------
|   Insulation for Copper  |
----------------------------
| 60degC | 75degC | 90degC |
|  Type  |  Type  |  Type  |
----------------------------
|        |        | FEP    |
|        |        | FEPB   |
|        |        | MI     |
|        |        | RHH    |
|        |  RHW   | RHW-2  |
|        |        | SA     |
|        |        | SIS    |
|        |        | TBS    |
|        |        | THHN   |
|   TW   |  THHW  | THHW   |
|        |  THW   | THW-2  |
|        |  THWN  | THWN-2 |
|   UF   |  USE   | USE-2  |
|        |        | XHH    |
|        |  XHHW  | XHHW   |
|        |        | XHHW-2 |
|        |  ZW    | ZW-2   |
----------------------------

1.3) Aluminum or Copper-clad Aluminum Wire Ampacities
---------------------------------------
| Aluminum |  Insulation Max Op. Temp |
---------------------------------------
|   Area   | 60degC | 75degC | 90degC |
|   mm^2   |  Amps  |  Amps  |  Amps  |
---------------------------------------
|    3.5   |    15  |    20  |    25  |
|    5.5   |    25  |    30  |    35  |
|    8.0   |    30  |    40  |    45  |
|   14.0   |    40  |    50  |    65  |
|   22.0   |    55  |    65  |    80  |
|   30.0   |    65  |    80  |    90  |
|   38.0   |    75  |    90  |   105  |
|   50.0   |    90  |   110  |   125  |
|   60.0   |   100  |   120  |   135  |
|   80.0   |   120  |   145  |   165  |
|  100.0   |   140  |   170  |   190  |
|  125.0   |   165  |   200  |   225  |
|  150.0   |   190  |   230  |   255  |
|  175.0   |   205  |   245  |   275  |
|  200.0   |   220  |   265  |   300  |
|  250.0   |   255  |   305  |   345  |
|  325.0   |   300  |   355  |   405  |
|  375.0   |   315  |   380  |   430  |
|  400.0   |   320  |   385  |   440  |
|  500.0   |   365  |   435  |   485  |
---------------------------------------

1.4.) Aluminum or Copper-clad Aluminum Wire Insulators
----------------------------
|  Insulation for Aluminum |
----------------------------
| 60degC | 75degC | 90degC |
|  Type  |  Type  |  Type  |
----------------------------
|        |        | RHH    |
|        |  RHW   | RHW-2  |
|        |        | SA     |
|        |        | SIS    |
|        |        | TBS    |
|        |        | THHN   |
|   TW   |  THHW  | THHW   |
|        |  THW   | THW-2  |
|        |  THWN  | THWN-2 |
|   UF   |  USE   | USE-2  |
|        |        | XHH    |
|        |  XHHW  | XHHW   |
|        |        | XHHW-2 |
|        |        | ZW-2   |
----------------------------

2.) Alternating-Current Resistance and Reactance of Cables in Conduit

The areas, resistances, and reactances of the following tables are based on 2017 PEC Table 10.1.1.9 [ or 2017 NEC Chapter 9 Table 9 ].

2.1.) Copper Wire Impedances
---------------------------------------------------------------
|  Copper  |    Impedance [R, X] ohms/305m. (305m = 1000ft)   |
---------------------------------------------------------------
|   Area   |       PVC      |    Aluminum    |      Steel     |
|   mm^2   |     conduit    |    conduit     |     conduit    |
---------------------------------------------------------------
|    2.0   | [3.100, 0.058] | [3.100, 0.058] | [3.100, 0.073] |
|    3.5   | [2.000, 0.054] | [2.000, 0.054] | [2.000, 0.068] |
|    5.5   | [1.200, 0.050] | [1.200, 0.050] | [1.200, 0.063] |
|    8.0   | [0.780, 0.052] | [0.780, 0.052] | [0.780, 0.065] |
|   14.0   | [0.490, 0.051] | [0.490, 0.051] | [0.490, 0.064] |
|   22.0   | [0.310, 0.048] | [0.310, 0.048] | [0.310, 0.060] |
|   30.0   | [0.190, 0.045] | [0.200, 0.045] | [0.200, 0.057] |
|   38.0   | [0.150, 0.046] | [0.160, 0.046] | [0.160, 0.057] |
|   50.0   | [0.120, 0.044] | [0.130, 0.044] | [0.120, 0.055] |
|   60.0   | [0.100, 0.043] | [0.100, 0.043] | [0.100, 0.054] |
|   80.0   | [0.077, 0.042] | [0.082, 0.042] | [0.079, 0.052] |
|  100.0   | [0.062, 0.041] | [0.067, 0.041] | [0.063, 0.051] |
|  125.0   | [0.052, 0.041] | [0.057, 0.041] | [0.054, 0.052] |
|  150.0   | [0.044, 0.041] | [0.049, 0.041] | [0.045, 0.051] |
|  175.0   | [0.038, 0.040] | [0.043, 0.040] | [0.039, 0.050] |
|  200.0   | [0.033, 0.040] | [0.038, 0.040] | [0.035, 0.049] |
|  250.0   | [0.027, 0.039] | [0.032, 0.039] | [0.029, 0.048] |
|  325.0   | [0.023, 0.039] | [0.028, 0.039] | [0.025, 0.048] |
|  375.0   | [0.019, 0.038] | [0.024, 0.038] | [0.021, 0.048] |
|  400.0   | [0.019, 0.038] | [0.024, 0.038] | [0.021, 0.048] |
|  500.0   | [0.015, 0.037] | [0.019, 0.037] | [0.018, 0.046] |
---------------------------------------------------------------

2.2.) Aluminum Wire Impedances
---------------------------------------------------------------
| Aluminum |    Impedance [R, X] ohms/305m. (305m = 1000ft)   |
---------------------------------------------------------------
|   Area   |       PVC      |    Aluminum    |      Steel     |
|   mm^2   |     conduit    |    conduit     |     conduit    |
---------------------------------------------------------------
|    3.5   | [3.200, 0.054] | [3.200, 0.054] | [3.200, 0.068] |
|    5.5   | [2.000, 0.050] | [2.000, 0.050] | [2.000, 0.063] |
|    8.0   | [1.300, 0.052] | [1.300, 0.052] | [1.300, 0.065] |
|   14.0   | [0.810, 0.051] | [0.810, 0.051] | [0.810, 0.064] |
|   22.0   | [0.510, 0.048] | [0.510, 0.048] | [0.510, 0.060] |
|   30.0   | [0.320, 0.045] | [0.320, 0.045] | [0.320, 0.057] |
|   38.0   | [0.250, 0.046] | [0.260, 0.046] | [0.250, 0.057] |
|   50.0   | [0.200, 0.044] | [0.210, 0.044] | [0.200, 0.055] |
|   60.0   | [0.160, 0.043] | [0.160, 0.043] | [0.160, 0.054] |
|   80.0   | [0.130, 0.042] | [0.130, 0.042] | [0.130, 0.052] |
|  100.0   | [0.100, 0.041] | [0.110, 0.041] | [0.100, 0.051] |
|  125.0   | [0.085, 0.041] | [0.090, 0.041] | [0.086, 0.052] |
|  150.0   | [0.071, 0.041] | [0.076, 0.041] | [0.072, 0.051] |
|  175.0   | [0.061, 0.040] | [0.066, 0.040] | [0.063, 0.050] |
|  200.0   | [0.054, 0.040] | [0.059, 0.040] | [0.055, 0.049] |
|  250.0   | [0.043, 0.039] | [0.048, 0.039] | [0.045, 0.048] |
|  325.0   | [0.036, 0.039] | [0.041, 0.039] | [0.038, 0.048] |
|  375.0   | [0.029, 0.038] | [0.034, 0.038] | [0.031, 0.048] |
|  400.0   | [0.029, 0.038] | [0.034, 0.038] | [0.031, 0.048] |
|  500.0   | [0.023, 0.037] | [0.027, 0.037] | [0.025, 0.046] |
---------------------------------------------------------------

==========

REFERENCES

1.) Philippine Electrical Code (SI Modernized Metric System)

1.1.) 2017 PEC Table 3.10.2.6(B)(16) Allowable Ampacities of Insulated Conductors Rated Up to and Including 2000 Volts, 60degC Through 90degC, Not More Than Three Current-Carrying Conductors in Raceway, Cable, or Earth (Directly Buried), Based on Ambient Temperature of 30degC.

1.2.) 2017 PEC Table 10.1.1.9 Alternating-Current Resistance and Reactance for 600-Volt Cables, 3-Phase, 60Hz, 75degC - Three Single Conductors in Conduit.

2.) National Electrical Code (US Inch-Pound System)

2.1.) 2017 NEC Table 310.15(B)(16) Allowable Ampacities of Insulated Conductors Rated Up to and Including 2000 Volts, 60degC Through 90degC (140degF Through 194degF), Not More Than Three Current-Carrying Conductors in Raceway, Cable, or Earth (Directly Buried), Based on Ambient Temperature of 30degC (86degF).

2.2.) 2017 NEC Chapter 9 Table 9 Alternating-Current Resistance and Reactance for 600-Volt Cables, 3-Phase, 60Hz, 75degC (167degF) - Three Single Conductors in Conduit.

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