1. ANNEX E PRESENTER WINSTON THOMAS
TTS 171 : PART 1: 2002
ANNEX E
PRESENTER
WINSTON THOMAS
ELECTRICAL INSPECTOR 1

2. MAXIMUM CONDUCTORS IN CONDUIT AND BOXES
Objective
Simple guide
Calculation

3. Cont’d.
Maximum number of cables
Conduits
Boxes

4. CONDUITS
Electrical Metallic Tubing or E.M.T
Steel heavy gauge conduit
PVC conduit

5. APPLICATION
Surroundings
Ambient temperature
Level of mechanical
protection

6. CAPACITIES
For the maximum capacities
Reference to Annex E
Relevant table

7. TABLES IN ANNEX E Maximum PVC insulated non sheathed cables
Four tables
Maximum PVC insulated
non sheathed cables
Space factor of 40 %

8. Cont’d.
Two 900 bends
Additional bends
Cables reduced

9. USE OF TABLES for circuit Choose cable size in column
Calculate number of cables
for circuit
Choose cable size in column
Use maximum number of cables column

10. Cont’d.
Choose value equal to or
greater than number of
cables
Go to corresponding column
for conduit size

11. TABLE E 2a
Covers maximum capacities
Steel conduit and E.M.T
PVC insulated non-sheathed
single core cables

12. Same cross-sectional area Imperial, AWG or MCM and Metric sizes
Cont’d.
Same cross-sectional area
Imperial, AWG or MCM
and Metric sizes

14. Example
A 115/230V single phase a.c
circuit requiring 16mm2 single
core cables is to be run in an
E.M.T conduit .
To determine conduit size.

15. Calculate Number of cables. (3)
Cable size column. (16mm2)
Maximum number cables column. (4)
Corresponding conduit size of 27 mm or (1 in).

17. Steel heavy gauge conduits.
Table E 2b
Covers maximum capacities.
Steel heavy gauge conduits.
PVC insulated cables of same cross-sectional area.

19. Example
Using three 16mm2 cables as in
the previous example.
Follow same steps.
Conduit size approximately the
same.(25mm)

21. Table E 2c
Covers maximum capacities.
PVC conduits
PVC insulated cables of same cross-sectional area

23. Example
Same circuit to be run in PVC
conduit.
A grounding conductor is now
required.
Number of cables. ( 4 )

24. Cont’d
Maximum number of cables
column. (5)
Conduit size - 32mm

26. Table E1
New addition to code.
Covers maximum capacities.
All types of conduits.

27. PVC insulated cables of different cross-sectional areas
Cont’d
PVC insulated cables of different cross-sectional areas
Conduit factor
Conductor factor .

29. Total conductor factor = Sum of cable conductor factors.
Example
Four 2.5mm 2 , four 4.0mm 2 and
two 6.0mm 2 cables, are to be
drawn into a conduit.
Total conductor factor = Sum of
cable conductor factors.

30. Cont’d.
Conduit factor shall be equal
to or greater than total
conductor factor.

31. Total 376 Conduit factor - 486 Conduit 27mm ( 1 in. )
4 x 2.5mm 2 factor = 4 x 30 = 120
4 x 4.0mm2 factor = 4 x 39 = 156
2 x 6.0mm2 factor = 2 x 50 = 100
Total
Conduit factor
Conduit 27mm ( 1 in. )

33. Outlet and junction boxes
CAPACITIES OF BOXES
Table E 3
New addition to code.
Maximum capacities.
Outlet and junction boxes

35. Example
Sixteen 4.0mm2 cables to be
spliced in a box.
Determine size of box.
First go to column for 4.0mm
cables.

36. Cont’d.
Then to row where value is
equal to or greater than
sixteen.
Then to box in corresponding
row. (4 11/16 x 2 1/8)

38. THE END