Electrical Wire 101: The Importance of Choosing the Right Size

Nowadays, we’re living a life surrounded by tools, gadgets, and machines that are run by electricity. We’ve taken for granted the intricacies behind it. How an electric wire is needed for us to use and experience comfort throughout the day whether it be at work or at home. 

In this article, we’ll be focusing on electrical wires and the importance of choosing the right size when installing your solar generator in your home.

But first a brief history…

According to history, the earliest record of electrical cable used commercially was by the Telegraph in 1844. The line was from Washington, D.C., to Baltimore, Maryland. 

The first electrical cables were a bit problematic as they were not insulated. The design restricted the accommodation of a higher amount of current and from having multiple wires. The first ever insulated electrical wire was the rope twine. But it required a lot of time to weave the wire.

Electrical Wire 101: How it works and its parts

We all know how a hose works. It carries water from its source to our kitchen sinks and bathrooms. The larger the hose is, the less water flow resistance there is. That’s how electrical wire works as well. It brings the current from the source to places that require power. And, if the electrical wire’s copper gauge is bigger than necessary, or has a longer cable, then the resistance is affected. It may provide a higher resistance, which ends up in receiving fewer watts for your solar generator.  

The electrical wire consists of three main parts: 

• Insulation works to contain the electrical flow within the conductor. 

• The Conductor is responsible for channeling the electrical flow. It is typically made of copper, making it more flexible. 

• Mechanical Protection is the outer layer of the cable. It works to avoid any damage to the wire when installed and in use. 

The Wire Size and Wire Gauge

To determine what’s the right size for your solar generator pv system, be sure to check your wire gauge. 

The wire gauge is the physical size and current capacity of the electrical wire. It also refers to the amount of current the wires can safely carry without causing any damage. It has a fixed numerical designation, which is proportional to its conductor’s diameter and resistance.

Pro-tip: the lower the wire gauge number is, the larger the diameter is and the less resistance it will be. This results in a higher current.   

Also, each wire gauge has an equivalent Ampacity or the electrical current measure. 

 The Most Commonly Used Wire Gauge sizes 

To help you determine which is the best wire gauge to pick for your PV pv system, be sure to check the amount of current you need and for what purpose will it be used.

There are at least 30 wire gauge sizes on the American Wire Gauge (AWG) table, but provided below are the most commonly used gauged in residential settings:

Wire Gauge

AMPS

Appliances

14 Gauge

15 Amps

Lighting circuits, light fixtures

12 Gauge

20 Amps

Outdoor receptacles, kitchen, bathroom

10 Gauge

30 Amps

Electric clothes dryer, air conditioning

8 Gauge

40 Amps

Feeder and large appliance wire

6 Gauge

55 Amps

Feeder and large appliance war

3 Gauge

100 Amps

Feeder wire and service reentrance 

1/20 Gauge

150 Amps

Feeder wire and service entrance

3/10 Gauge

200 Amps

Service entrance

 

The AWG is introduced to the public in 1857. It is a means to standardize the measurement as different manufacturers have their own measurements back then in the US. The AWG is focused on the electrically conductive wire and does not include the insulation.

It’s all about safety and performance when choosing the right size and for AWG. By using the right size, all appliances, machines, and gadgets are working at their optimum prime consistently. This also ensures the safety of everyone in the home or building.

Solar Generators and the right wire gauge

For commercial solar PV panels, the electrical wire needed should be able to accommodate 50 watts which is about 10 gauge. This means up to 30 amps of current can come from a single solar panel. So, for multiple panels, a three to eight-gauge “combiner” set is needed for the power to safely flow through a charge controller. 

Alongside the gauge, the length of the wire/s must be the right length as this can affect a battery bank’s life. An oversize wire length is a waste of money, and an undersized wire can cause a short circuit.

Sizing the wire length correlates to the electrical demand of the appliances on the machine also known as the total load. Also, the voltage drop is considered when determining the length of the wire. This means that a loss of voltage occurred in the circuit because of the natural resistance of the wires. 

This is a normal occurrence but is not really a problem for indoor wiring because the circuit breaker is usually near, unlike outdoor circuits. Making it an important factor to take when installing solar generators as the panels are placed on rooftops and the charge controller is likely to be indoors. In general, the voltage drop should remain below 2%. 

Provided below is a chart that calculates the length for a 12v PV system that can be doubled or quadrupled for a 24v system and a 48v system.

2% Voltage Drop Chart

AWG

4

6

8

10

12

14

AMPS

70

55

40

30

20

15

Arrary Amps

Feet per pair of wires

1

456

290

180

115

70

45

2

228

145

90

57.5

35

22.5

4

114

72.5

45

27.5

17.5

10

6

75

47.5

30

17.5

12

7.5

8

57

35.5

22.5

11.5

8.5

5.5

10

45.5

28.5

18

9.5

7

4.5

15

30

19

12

7

4.5

3

20

22.5

14.5

9

5.5

3.5

2

25

18

11.5

7

4.5

2.8

1.8

 

To read this table, let’s say you have a 450-watt 12v system with a Vmp of 18v and a maximum current of 450/18, which is about 25 amps. 

Upon checking the table, the 10 AWG is the lowest gauge wire that can be used safely. Then on the Array amps, look at the row for 25, which you can see can support a length of 4.5 feet. 

This table goes to show that good planning is required when it comes to designing your solar generator panel system. That way every part and size of an electrical wire is used to its full capacity. Thus, you and your solar generator system are not wasting too much energy and money because of the length and to compensate for the unnecessary voltage drop.

But if all of this gauge talk is confusing, then be sure to check in with your local electrician or just give us a shout here so we can assist you further. 

* We want to give credit where credit is due. Professional writer, Cris Ilao, contributed research and content to this blog titled: Electrical Wire 101: The Importance of Choosing the Right Size Thank you, Cris, for your contributions!