Post by GuglioLS on Feb 3, 2008 2:00:52 GMT -5
I have done some research into the minimum size gauge wire required to carry DC power through a wire. I thought I would share the research in hopes of providing a reference and guide to adding circuits to our tractors. Do not confuse minimum wire size needed by comparing to house wiring. Low voltage DC behaves very differently than household AC current. Additionally, wire used in homes is solid, wire used in automotive applications is stranded.
The wire sizes in the table are based on a typical length of wire run encountered when wiring an automobile. Since the length of wire found in our Tractors is relatively short, and the wattage fairly low, When adding additional circuits the below table should give you a good general idea what wire size to use.
For longer runs or for those who wish to use the exact wire size based on current and length, use the chart below. Match the current draw to the length of wire needed to select the appropriate wire gauge. For Example, your installing a 20 amp cigarette lighter that's 10' from the power source - on the top column go to 10' then on the left row go to 20 amps, the wire size to use is where the two intersect, in this case it's 16 gauge.
This seems like a small gauge wire for 20 amps, but do not fear for low voltage DC and only 10 feet, it's more than adequate.
AMPS / length
Using a lower gauge number (Bigger wire) is OK to use but gives no advantage, as the amount of power capacity gained would never be noticed.
When electricity flows through a wire, it mostly flows on the surface of the wire, not through the middle.This means that a wire of a given size that's made up of many smaller strands can carry more power than a solid wire - simply because the stranded wire has more surface area. This is one reason why battery cables in your car and welding cables are made up of many very fine strands of smaller wire - it allows them to safely carry more power with less of that power being dissipated as heat. The other reason stranded wires are used is flexibility.
Not all may agree with this research and I respect that, some like to use "monster cable" to carry small amounts of DC current. They have been deceived by marketing campaigns to buy the biggest, most expensive, highest profit margin wire on the market. All I can say is More Power to them.
Larry
The wire sizes in the table are based on a typical length of wire run encountered when wiring an automobile. Since the length of wire found in our Tractors is relatively short, and the wattage fairly low, When adding additional circuits the below table should give you a good general idea what wire size to use.
| Air Conditioning- 10 GAUGE Alternator- 10 GAUGE Ammeter- 10 GAUGE Cigarette Lighter- 14 GAUGE Clock- 18 GAUGE Coil Wire- 16 GAUGE Dome Lights- 16 GAUGE Driving Lights- 14 GAUGE Gauges- 14 GAUGE Generator (Charging)- 10 GAUGE Generator To Starter- 16 GAUGE Headlight Circuit- 14 GAUGE Headlight Switch To Fuse Block- 12 GAUGE Heater Leads- 16 GAUGE | Heater Switch- 10 GAUGE Horn Button- 18 GAUGE Horn To Relay- 10 GAUGE Ignition Switch – 12 GAUGE Low-Amps Circuits- 18 GAUGE Parking Lights- 16 GAUGE Radio To Fuse Blocks- 14 GAUGE Single Bulbs- 18 GAUGE Starter To Relay- 16 GAUGE Stoplights- 16 GAUGE Tail Lights- 16 GAUGE Turn Signals- 16 GAUGE CD To Fuse Block- 14 GAUGE Windshield Wiper & Washer- 14 GAUGE |
For longer runs or for those who wish to use the exact wire size based on current and length, use the chart below. Match the current draw to the length of wire needed to select the appropriate wire gauge. For Example, your installing a 20 amp cigarette lighter that's 10' from the power source - on the top column go to 10' then on the left row go to 20 amps, the wire size to use is where the two intersect, in this case it's 16 gauge.
This seems like a small gauge wire for 20 amps, but do not fear for low voltage DC and only 10 feet, it's more than adequate.
This Table is based on Stranded wire, low voltage DC, less than or equal to 2% power loss
AMPS / length
3' 5' 7' 10' 15' 20' 25'
0 to 5 18 18 18 18 18 18 18
6 18 18 18 18 18 18 18
7 18 18 18 18 18 18 18
8 18 18 18 18 18 16 16
10 18 18 18 18 16 16 16
11 18 18 18 18 16 16 14
12 18 18 18 18 16 16 14
15 18 18 18 18 14 14 12
18 18 18 16 16 14 14 12
20 18 18 16 16 14 12 10
22 18 18 16 16 12 12 10
24 18 18 16 16 12 12 10
30 18 16 16 14 10 10 10
40 18 16 14 12 10 10 8
50 16 14 12 12 10 10 8
100 12 12 10 10 6 6 4
150 10 10 8 8 4 4 2
200 10 8 8 6 4 4 2
Using a lower gauge number (Bigger wire) is OK to use but gives no advantage, as the amount of power capacity gained would never be noticed.
When electricity flows through a wire, it mostly flows on the surface of the wire, not through the middle.This means that a wire of a given size that's made up of many smaller strands can carry more power than a solid wire - simply because the stranded wire has more surface area. This is one reason why battery cables in your car and welding cables are made up of many very fine strands of smaller wire - it allows them to safely carry more power with less of that power being dissipated as heat. The other reason stranded wires are used is flexibility.
Not all may agree with this research and I respect that, some like to use "monster cable" to carry small amounts of DC current. They have been deceived by marketing campaigns to buy the biggest, most expensive, highest profit margin wire on the market. All I can say is More Power to them.
Larry
