In Article " Conductor Ampacity Calculation – Part Twelve ", I explained the following:
 Third: Tables Group#3: adjustment factor tables, which includes TABLE B.310.15(B)(2)(11).
 Fourth: Figures Group#1: adjustment figure for Thermal Resistivity and Load Factor, which includes Figure B.310.15(B)(2)(1).
 Fifth: Figures Group#2A: Detail Figures Which includes B.310.15(B)(2)(2).
 TABLE B.310.15(B)(2)(8) in Accordance with Figure B.310.15(B)(2)(2),
 TABLE B.310.15(B)(2)(9) in Accordance with Figure B.310.15(B)(2)(2),
 TABLE B.310.15(B)(2)(10) in Accordance with Figure B.310.15(B)(2)(2),
Also,In Article " Conductor Ampacity Calculation – Part Ten ", I explained how to use the Annex B Tables included under Group#2A “ tables for conductors installed in underground electrical duct bank” which includes:
 TABLE B.310.15(B)(2)(5) in Accordance with Figure B.310.15(B)(2)(2),
 TABLE B.310.15(B)(2)(6) in Accordance with Figure B.310.15(B)(2)(2),
 TABLE B.310.15(B)(2)(7) in Accordance with Figure B.310.15(B)(2)(2),
Today, I will explain how to use Other Annex B tables and figures.
For more information about the Second method for Conductors ampacity calculations by using Annex B Tables under engineering supervision, please review the following articles:
For more information about the first method for Conductors ampacity calculations by using Tables as provided in 310.15(B), please review the following articles:
Using Annex B tables and figures:
Rule#1: Annex B Tables And
Figures
Annex B consists of
many tables and figures as follows:
1 Tables:
2 Figures:
The following
figures represent Underground electrical duct bank configurations:

To download a PDF copy of Annex B tables and figures, click on the link.
The above tables can be divided to groups as follows:
 Tables Group#1: tables for conductors installed in free air.
 Tables Group#2: tables for conductors installed in underground electrical duct bank tables.
 Tables Group#3: adjustment factor tables
 Figures Group#1: adjustment figure for Thermal Resistivity and Load Factor.
 Figures Group#2A: Detail Figures.
 Figures Group#2B: special case figures.
Sixth: Figures Group#2B: special case figures
This tables group includes three figures as follows:
 Figure B.310.15(B)(2)(3),
 Figure B.310.15(B)(2)(4),
 Figure B.310.15(B)(2)(5).
1 Figure B.310.15(B)(2)(3):
1.1 Construction:
Figure B.310.15(B)(2)(3) shows Ampacities of Single Insulated Conductors Rated 0 through 5000 Volts in Underground Electrical Ducts (Three Conductors per Electrical Duct), Nine SingleConductor Cables per Phase Based on Ambient Earth Temperature of 20°C (68°F), Conductor Temperature 75°C (167°F).
Figure B.310.15(B)(2)(3) consists of:
 Detail and Design criteria,
 Table,
 Notes.
1 Detail and Design criteria
Detail are as per fig.1 below which must be used under the following design criteria:

Fig (1) 
Important!!!
If the above design criteria is verified for fig.1 above, table of Figure B.310.15(B)(2)(3) can be applied.

2 Table
2.1 Conditions For Table Application
These conditions are existing in the Figure description at the bottom of the figure Figure B.310.15(B)(2)(3), which are:
2.2 Allowable Insulation materials
2.3 Two Conductor Sizes Columns (Right and Left)
In these two right and left Two Conductor Sizes Columns, Three Conductor sizes are permitted to be used under Figure B.310.15(B)(2)(3), which are 250, 350 and 500 Kcmil.
2.4 three Columns for Thermal resistivity (RHO) and Load Factor (LF) Values
certain values of Thermal resistivity (RHO) and Load Factor (LF) permitted to be used under Figure B.310.15(B)(2)(3) as follows:
2.5 Correction Factors for Ambient Temperature
This section of Correction Factors for Ambient Temperature gives the value of a correction factor for Ambient Temperature (other than 20°C (68°F)) based on the Actual Ambient temperature columns in the right and left of this section.

3 Notes

2 Figure
B.310.15(B)(2)(4):
2.1 Construction:
Figure B.310.15(B)(2)(4) shows Ampacities of
Single Insulated Conductors Rated 0 through
5000 Volts in Nonmagnetic Underground
Electrical Ducts (One Conductor per Electrical Duct), Four SingleConductor Cables
per Phase Based on Ambient Earth Temperature of 20°C (68°F), Conductor
Temperature 75°C (167°F).
Figure
B.310.15(B)(2)(4) consists of:
 Detail and Design criteria,
 Table,
 Notes.
1 Detail and Design criteria
Detail are as per fig.2 below which must be used under the following design criteria:

Fig (2) 
Important!!!
If the above design criteria is verified for fig.2 above, table of Figure B.310.15(B)(2)(4) can be applied.

2 Table
2.1 Conditions For Table Application
These conditions are existing in the Figure description at the bottom of the figure Figure B.310.15(B)(2)(4), which are:
2.2 Allowable Insulation materials
2.3 Two Conductor Sizes Columns (Right and Left)
In these two right and left Two Conductor Sizes Columns, five Conductor sizes are permitted to be used under Figure B.310.15(B)(2)(3), which are as below table:
2.4 three Columns for Thermal resistivity (RHO) and Load Factor (LF) Values
certain values of Thermal resistivity (RHO) and Load Factor (LF) permitted to be used under Figure B.310.15(B)(2)(3) as follows:
2.5 Correction Factors for Ambient Temperature
This section of Correction Factors for Ambient Temperature gives the value of a correction factor for Ambient Temperature (other than 20°C (68°F)) based on the Actual Ambient temperature columns in the right and left of this section.

3 Notes

3 Figure
B.310.15(B)(2)(5):
3.1 Construction:
Figure B.310.15(B)(2)(5) shows Ampacities of
Single Insulated Conductors Rated 0 through
5000 Volts in Nonmagnetic Underground
Electrical Ducts (One Conductor per Electrical Duct), Five SingleConductor Cables
per Phase Based on Ambient Earth Temperature of 20°C (68°F), Conductor
Temperature 75°C (167°F).
Figure
B.310.15(B)(2)(5) consists of:
 Detail and Design criteria,
 Table,
 Notes.
1 Detail and Design criteria
Detail are as per fig.3 below which must be used under the following design criteria:

Fig (3) 
Important!!!
If the above design criteria is verified for fig.3 above, table of Figure B.310.15(B)(2)(5) can be applied.

2 Table
2.1 Conditions For Table Application
These conditions are existing in the Figure description at the bottom of the figure Figure B.310.15(B)(2)(4), which are:
2.2 Allowable Insulation materials
2.3 Two Conductor Sizes Columns (Right and Left)
In these two right and left Two Conductor Sizes Columns, one Conductor size is permitted to be used under Figure B.310.15(B)(2)(3), which is 2000 Kcmil.
2.4 three Columns for Thermal resistivity (RHO) and Load Factor (LF) Values
certain values of Thermal resistivity (RHO) and Load Factor (LF) permitted to be used under Figure B.310.15(B)(2)(3) as follows:
2.5 Correction Factors for Ambient Temperature
This section of Correction Factors for Ambient Temperature gives the value of a correction factor for Ambient Temperature (other than 20°C (68°F)) based on the Actual Ambient temperature columns in the right and left of this section.

3
Notes

4 Differences between (3) special
case figures:
Figure B.310.15(B)(2)(3)

Figure B.310.15(B)(2)(4)

Figure B.310.15(B)(2)(5)


Duct
Type

Underground magnetic
or Nonmagnetic Electrical
Ducts

Nonmagnetic Underground Electrical Ducts

Nonmagnetic Underground Electrical

Number
of Cables per Duct

3

1

1

Number
of Cables per Phase

9

4

5

Conductor Sizes (Kcmil)

250 
350  500

750 –
1000 – 1250 – 1500  1750

2000

Phase
Ducts Size

75 to
125 mm (3 to 5 in.)

75 mm
(3 in.)

75 mm
(3 in.)

Phasing
Configurations

In case of Nonmagnetic Ducts, Phasing is A, B, C in rows or columns

Phasing is A, B, C in rows or columns

Phasing is A, B, C in rows or columns

In case of Nonmagnetic Ducts, conductors are installed A, B, C per
electrical duct with the neutral and all equipment grounding conductors in
the same electrical duct. In this case, the 6in. trade size neutral duct is
eliminated.

In the next Article, I will explain the
Voltage Drop Calculations. Please, keep following.
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