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Adaptaflex Product Catalogue |
LIT211GB 0715
8
Technical section
Cable carrying capacity (wire fill)
Introduction
UK Wiring regulations BS7671 recommend that the total
cross sectional area of the sum of individual cables shall not
exceed 40% of the cross sectional area of the conduit based
on using 3 or more cables. The tables below enable youto
calculate the number of conductors that can be run within a
piece of flexible conduit.
Instructions
–
Step 1:
Establish the number and size of each wire to be
run in the conduit
–
Step 2:
Look on the Cross Sectional Area (CSA) chart
(table 1), look up the CSA taken up by each of the wires
from STEP 1
–
Step 3:
Add all the CSA values together (Total CSA)
–
Step 4:
Look on the conduit fill value chart (table 2).
– Choose a conduit with a 40% fill value higher than the total
CSA from STEP 3
Table 1 - Cross Sectional Area (CSA) Chart
Number of Wires
Nominal Conductor Size
1
2
3
4
5
10
15
20
1mm
6.6
13.2
19.8
26.4
33
66
99
132
1.5mm
7.6
15.2
22.8
30.4
38
76
114
152
2.5mm
9.6
19.2
28.8
38.4
48
96
144
192
4mm
14.5
29
43.5
58
72.5
145
217.5
290
6mm
18.8
37.6
56.4
75.2
94
188
282
376
10mm
29.3
58.6
87.9
117.2
146.5
293
439.5
586
16mm
40.2
80.4
120.6
160.8
201
402
603
804
25mm
63.8
127.6
191.4
255.2
319
638
957
1276
35mm
83.5
167
250.5
334
417.5
835
1252
1670
50mm
113
226
339
452
565
1130
1695
2260
70mm
149
298
447
596
745
1490
2235
95mm
204
408
612
816
1020
2040
Table 2 - Wire Fill of Plastic & Metallic Conduit
Plastic Conduit
Metallic Conduit
Nominal Diameter
100% Fill
40% Fill
100% Fill
40% Fill
10mm
33.2
13
25.5
10.2
13mm
72.4
29
58.1
23.2
16mm
109.4
44
83.3
33.3
18mm
158.4
63
160.6
64.2
21mm
213.8
86
243.3
97.3
28mm
369.8
148
452.4
181
34mm
602.6
241
855.3
342.1
42mm
973.1
390
1164.2
465.7
54mm
1698.2
680
1963.5
785.4
80mm
3520
1410
3473.2
1389.3
106mm
6500
2600
Example - What size of conduit to use?
–
Step 1:
4 x 2.5mm conductors, 2 x 10mm conductors and
3 x 50mm conductors
–
Step 2:
The CSA of Four 2.5mm conductors is 38.4, Two
10mm conductors is 58.6, Three 50mm conductors is 339
–
Step 3:
Total of these groups is 38.4 + 58.6 + 339 = 436
–
Step 4:
Using Table 2 the conduit is either 54mm (680)
Plastic or 50mm (465.7) Metallic
–
Note:
42mm Plastic is 390 which is smaller than 436
therefore not recommended
The information given above relates to PA - Standard weight
conduit and Adaptalok fittings or SPL with M-Type fittings.
It is given in good faith and should be used only as a guide in
conjunction with the relevant wiring regulations.