Copper cable

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Cable Diameter Standards

Area (metric) Diameter American Wire Gauge Resistance Ampacity Typical Use
0.08 mm² 0.32 mm AWG28 200 mΩ/m 0.8 A Thin wires inside a data cable
0.10 mm² 0.36 mm AWG27 160 mΩ/m 1 A Thin hobby wire (home electronics for up to 30cm)
0.14 mm² 0.40 mm AWG26 125 mΩ/m 1.3 A Cat5 UTP, Flexible hobby wire
0.25 mm² 0.50 mm AWG23 / AWG24 65 mΩ/m 3 A Cat5e UTP, breadboard wires, Thicker hobby wire
0.50 mm² 0.80 mm AWG20 / AWG21 32 mΩ/m 5 A High quality Cat6 STP, Low voltage power cable (e.g. for phone or doorbell or powering electronics)
0.75 mm² 1.0 mm AWG18 / AWG19 20 mΩ/m 10 A Power cable between outlet and device
1.5 mm² 1.3 mm AWG16 13 mΩ/m 12 A Thin power wire in walls (black wire for switches)
2.5 mm² 1.6 mm AWG14 8 mΩ/m 15 A Normal power wire in walls (power, zero and earth wire)
6.0 mm² 2.5 mm AWG10 3 mΩ/m 30 A Thick wire in electric panel (groepenkast)

The metric area is the advertised area, equivalent of mm² copper. The actual diameter, when translated from AWG specification may differ.

The ampacity is the sustained current that can be transported through the wire without exceeding its temperature rating. In this case, the Ampacity at 60°C is given. For higher acceptable temperatures (75°C or 90°C), multiply by 1.5. Peak currents may be 10 times larger if they are short enough (< 10 seconds).

Note that the thickness of the cable is determined by the current (amperage), not by the voltage or power. So a lower-voltage installation requires thicker cables than a higher-voltage installation with the same power consumption. The current (in Ampere) can be calculated by dividing the Power (in Watts) by the Voltage of the appliance.

The thickness of the insulation depends on the voltage, and is not mentioned in this table.

Other considerations

Core
solid or flexible. A solid core is often used for fixed wiring, and for breadboard wires. Flexible wire contain multiple small strands and is used for flexible cables.
Material
copper of CCA (copper cladded aluminium). Copper is considered slightly better. CCA is cheaper and is consider good enough.

Network Cabling

Ethernet Category Max. Frequency Max. Transmission Speed (@ Max. distance) Cable type Number of wires Remark
Cat3 16 MHz 10 Mbps @ 100m U/UTP 2 Obsolete. Used for voice.
Cat5 100 MHz 100 Mbps @ 100m U/UTP 8 (4 used) Obsolete. Replaced by Cat 5e.
Cat5e 100 MHz 1 Gbps @ 100m 10 Gbps @ 45m U/UTP 8
Cat6 250 MHz 1 Gbps @ 100m 10 Gbps @ 55m F/UTP 8 Has separator between the 4 wire pairs
Cat6a 500 MHz 10 Gbps @ 100m F/UTP 8
Cat7 500 MHz 10 Gbps @ 100m S/FTP 8 Uses GG45 or TERA connectors. Obsolete by Cat 6a
Cat7a 600 MHz 10 Gbps @ 100m S/FTP 8 Obsolete by Cat 8
Cat8.1 2000 MHz 40 Gbps @ 30m U/FTP 8 Uses regular 8P8C ("RJ45") connectors.
Cat8.2 2000 MHz 40 Gbps @ 30m S/FTP 8 Uses GG45 or TERA connectors.

Shielding

Systematic Name Old name Cable protection Wire-pair protection
U/UTP UTP None None
U/FTP STP None Foil
F/UTP FTP, STP Foil None
S/UTP Braiding None
SF/UTP S-FTP Braiding and foil None
F/FTP FFTP Foil Foil
S/FTP SFTP Braiding Foil
SF/FTP Braiding and foil Foil
U = unshielded
F = foil shielding
S = braided shielding (outer layer only)
TP = twisted pair

When shielding is applied to a collection of pairs, it is usually referred to as screening, hence STP (Shielded Twisted Pair) is sometimes abbreviated to ScTP (Screened Twisted Pair).

Power over Ethernet

Name Passive PoE PoE PoE+ 4PPoE
Standard Non-standard 802.3af (802.3at Type 1) 802.3at Type 2 802.3bt Type 3 802.3bt Type 4
Power available at device 9.0 W 12.95 W 25.50 W 51 W 71 W
Maximum power delivered by power supply 12.0 W 15.40 W 30.0 W 60 W 100 W
Voltage range (at power supply) 24.0 V 44.0–57.0 V 50.0–57.0 V 50.0–57.0 V 52.0–57.0 V
Voltage range (at device) 17.5-24.0V 37.0–57.0 V 42.5–57.0 V 42.5–57.0 V 41.1–57.0 V
Maximum current Imax 500 mA 350 mA 600 mA 600 mA per pair 960 mA per pair
Maximum cable resistance per pairset 8 Ω (2× 4 Ω) 20 Ω (2× 10 Ω) 12.5 Ω (2× 6.25 Ω) 12.5 Ω (2× 6.25 Ω) 12.5 Ω (2× 6.25 Ω)
Power management None (always on) Three power class levels negotiated by signature Four power class levels negotiated by signature or 0.1 W steps negotiated by LLDP Three power class levels negotiated by signature or 0.1 W steps negotiated by LLDP 0.1 W steps negotiated by LLDP
Derating of maximum cable ambient operating temperature None None 5°C with one mode (two pairs) active 10°C with more than half of bundled cables pairs at Imax 10°C with temperature planning required
Supported cabling Category 5 Category 3 and Category 5 Category 5 Category 5 Category 5

Note that there are many "Passive PoE" applications. The given 24V is common for Ubiquiti devices that support Passive PoE. Other applications carry up to 1.0 A at 24V, 48V or even 56V.

Example Calculation

The tables allow for calculations of power budget of PoE devices. Imagine an access point powered by 24V passive PoE, using a good Cat 5e cable, which has a 42 mΩ/m resistance. A 15 meter cable has 30 m wire (going forth and back) and has thus 12.6 Ω resistance in total. With a maximum current of 0.5 A (determined from either the PoE table or the Ampacity of AWG22 wire), this translated to a drop in voltage of 0.63 Volt. Thus only 23.37 Volt of the original 24 Volt is left for the access point, translating to maximum of 11.7 Watt (with the 0.5 A).

In general, you will find that there is no problem with short cable of 10 or 20 meter, but you may hit power limitations when using a cable of the maximum length of 100 meter.

Further Reading

For UTP cabling: