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Wire Sizes

Cables Wires and Conductors
A wire is a single rod of metal with a small ratio of diameter to length.
A conductor is a wire suitable for carrying an electric current.
A stranded conductor is a conductor made up of a group of wires. These wires are usually twisted together.
A cable is either a single stranded conductor or a combination of conductors insulated from one another (a mutlti-core cable). Cables in the oil and gas and petrochem industries are generally always insulated and often protected with an armoured sheath. In general, stranded conductors are more flexible and less susceptible to fatigue-failure than solid wires.
 
Cable Sizing
Wires can carry only a limited amount of current safely. If the current flowing through a wire exceeds the current-carrying capacity of the wire, excess heat is generated. This heat may be great enough to burn off the insulation around the wire and start a fire. An increase in the diameter, or cross section, of a wire conductor decreases its resistance and increases its capacity to carry current.
Other reasons for choosing an increased cross sectional area of wire is to limit volt drop along its length.
 
Limitations
Wires and cables are made in standard diameters. When selecting cables it is common select the next standard size up from that calculated.
The terminals (e.g. Weidmuller, Phoenix etc) into which the cable or wire will terminate are made to accomadate a range of sizes. Be aware of any limitations this may place on your selection.
 
Dimensions
Wire diameters are often specified in American Wire Gausge (AWG) rather than in mm or inches. The charts below give dimensions of common diameters and the corresponding AWG.
 
Solid Bare Copper Wire
AWGNominal
Diam
(mm)
Cross
Section
(mm2)
102.65.23
112.34.155
122.053.29
131.832.63
141.632.07
151.451.651
161.291.3
171.151.039
181.020.816
190.9120.653
200.8130.514
210.7240.412
220.6430.322
230.5740.259
240.5110.203
250.4550.163
260.4040.127
270.3610.102
280.320.08
290.2870.064
300.2540.051
310.2260.04
320.2030.032
330.180.025
340.160.02
350.1420.016
360.1270.013
370.1140.01
380.1020.008
390.0890.006
400.0790.005
Stranded Tinned Copper Wire
AWGStranding
 
No/AWG
Nominal
Diam
(mm)
Cross
Section
(mm2)
127/202.443.61
1219/252.363.07
1265/302.413.27
147/221.852.26
1419/261.851.93
1442/301.852.06
167/241.521.42
1619/291.471.216
1665/341.51.3
187/261.220.891
1819/301.240.957
1842/341.20.819
1865/361.20.845
207/280.890.504
2019/320.940.612
2042/360.9140.533
227/300.7620.352
2219/340.7870.38
247/320.610.226
2419/360.610.239
2442/400.5840.201
267/340.4830.14
2619/380.5080.153
287/360.3810.071
2819/400.4060.093
307/380.3050.056

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Further Reading


 
17th Edition IEE Wiring Regulations: Explained and Illustrated
C & I reources and instrument utilities

C&I Resources

 
ATEX
Cable Gland Selector
CE Marking
Flange Dimensions
Ingress Protection
Pipe Schedules
Relief Valve Orifice Size
Temperature Class
Temperature Conversion
Thermocouple Types
Valve Leakage
Vortex Meters
Wires and Cables
 

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