In addition to that, you should always follow the NEC rule when choosing the wire for a sub-panel. You need to choose the right type of wire for your electrical sub panel.īecause choosing the wrong wire may not be able to suit the electric flow and cause a lot of nuisances.
:max_bytes(150000):strip_icc()/sub-panels-for-additional-space-1152719-02-005eee12f5f94074916b97746345058d.jpg "Wire size for 100 amp subpanel (2)")
Generally, wiring is one of the most essential parts of electrical work that is being done to ensure proper power supply throughout the house. You should make sure that the wire you are using to run 100 amps up panel should be sufficient to the amperage of the sub panel to provide you with proper electricity flow. Generally, the wire that is suitable to run a 100amp subpanel is #4 copper wires or #2 aluminum wires. Generally, a 100 amp sub panel requires #4 copper wires or #2 aluminum wires. When choosing the wire for a 100 amp subpanel, you need to make sure that the wire gorge is sufficient for the amperage of the sub panel. Generally, the #4 AWG has 85A ampacity but should conduct at most 68 amps.
It is ideal to wire the circuit to hit 80% ampacity. When running the subpanel, you should never put the circuit under 100% ampacity. However, when adding or servicing a 100 Amp wire(s), it is highly recommended to consult and even hire a certified electrician who is aware of local standards and laws regarding electric wiring. So, if You need to know the solid copper wire thickness for 100 Amps service/sub-panel, then: When calculating the wire thickness of the long wires, always use values from the 60☌/140☏ column, since the "wire length" rule, especially after calculating the "80% Rule" is all about energy losses and not wire surface temperature - as long as the wires are properly installed. Now, we have to check the required AWG value for given wire lengths, depending on the wire surface temperature - values are given in the following chart: Wire Length / Surface feet (125 Amps) There are several rules and standards that may be used when calculating the required wire thickness, but the general rule of thumb is to increase the required Ampacity by 10% for every 50 feet (~15 m) of the wire length - some standards increase Ampacity by 20% for every 100 feet (~30 m) which provides the same or very similar results.įor example, when calculating the required Ampacity for the 50 feet, 100 feet, 150 feet, and 200 feet wires, we can use (default value is 125 Amp, after applying the "80% Rule"):ĥ0 feet wire: Ampacity = 125 Amps * 1.1 = 137.5 Ampsġ00 feet wire: Ampacity = 125 Amps * 1.2 = 150 Ampsġ50 feet wire: Ampacity = 125 Amps * 1.3 = 162.5 AmpsĢ00 feet wire: Ampacity = 125 Amps * 1.4 = 175 Amps 90☌/194☏: 2 gauge wire (AWG 2) features an Ampacity of 130A.Īnd these values are for relatively short wires, usually less than 50 feet (less than ~15 meters), which raises the question about the wire thickness of longer wires. 75☌/167☏: 1 gauge wire (AWG 1) features an Ampacity of 130A, 60☌/140☏: 0 gauge wire (AWG 0) features an Ampacity of 125A, Thus, for 100 Amp service, the required wire thickness is: Hence, we should not look for wires being able to carry 100 Amps, but 125 Amps:
The 80% Safety RuleĨ0% Rule states that actual wire current should be at most 80% of its default Ampacity. 90☌/194☏: 3 gauge wire (AWG 3) features an Ampacity of 115A.īut, these wire thicknesses are not recommended for actual use since wires should never carry current that equals their default values for safety reasons - hence the 80% Rule. 75☌/167☏: 3 gauge wire (AWG 3) features an Ampacity of 100A, 60☌/140☏: 1 gauge wire (AWG 1) features an Ampacity of 115A, Note: Ampacities are given for enclosed wires ambient temperatures.Īs one can see, the Ampacity of wires is given at three different temperatures (60☌/140☏, 75☌/167☏, and 90☌/194☏), but for most residential installations, 60☌/140☏ is the maximum allowed wire surface temperature.Īlso, if the value is not given for a required current, one has to look for a wire with a larger Ampacity.įor example, if we are going to look for 100 Amp wire size using default Ampacities for solid copper wire, then:
