DC Wiring Categories And Size Specifications

 

In DC setups wiring is crucial as compared to what we AC voltages systems, since it may lead to large power differences and performance of the tools, to put up an example a 24 volts DC setups with 2 volts drop due to loss in wiring would result in 20 times more power loss as compared to a 2 volts drops in a 220 volts AC setup. The most commonly practiced DC wiring voltage levels are 12V, 24, 48V, and based on our previous argument, the most important concern is power loss. Usually, we define a voltage drop index over the to calculate the power ratings and wire size in AWG units. The formula to calculate voltage drop index is as:

VDI = Amps X Feet  ÷

 % Voltage Drop x Voltage 

 

Table 1 Wire Size Against VDI for Copper

Wire Size	Area mm2	COPPER
AWG		VDI	Ampacity
16	1.31	1	10
14	2.08	2	15
12	3.31	3	20
10	5.26	5	30
8	8.37	8	55
6	13.3	12	75
4	21.1	20	95
2	33.6	31	130
0	53.5	49	170
00	67.4	62	195

 

The values in the above table are calculated for copper using online available free tools. For other metals, these values could also be calculated easily with these tools available for public use. DC turns out to be much cheaper than AC as most of the product use converted DC at the last stage, as we know that an AC signal converted to DC may lose up to 45% power and hence it’s a good idea to implement the DC systems in the last stage of the devices.

The U.S. National Electrical Code (NEC) has defined some color codes for live neutral and ground wires which can be seen in the table below:

Table 2 US-NEC Defined Color Code for DC Wiring

System	Label	Color
Unearthed 2-Wire DC	Positive (L+)	Red
	Negative (L-)	Black
Earthed 3-Wire DC (Negative Earthed)	Positive (L+)	Red
	Negative (M)	White
Earthed 2-Wire DC (Positive Earthed)	Positive (M)	White
	Negative (L-)	Black
Earthed 3-Wire DC	Positive (L+)	Red
	Negative (M)	White
	Mid-Wire (L-)	Black
Protective Earth	Earth	Green, Yellow or Bare Conductor