By increasing the cross-section of the conductor (or increasing the size of the wire), the resistance decreases, and the allowable ampacity increases. However, the cross-sectional area of a conductor can also be changed to alter theĬonductor's resistance. The length of a conductor is directly proportional to its resistance. The heating of a conductor can be directly attributed from its Wire ampacity is calculated in such a way as to not exceed a certain temperature rise at a particular electrical load. However, many different external factors such as ambient temperature and conductor insulation play a part in determining In order to properly size a wire for your application, the ampacity ratings for a wire must be understood. The ampacity rating of a wire determines the amperage that a wire can safely Amperage is the measure of electricalĬurrent flowing through a circuit. Wire for many different applications can become complex and overwhelming. Wire to prevent overheating, fire and other dangerous conditions.
Wire size for 100 amp service code#
The National Electrical Code provides requirements for sizing electrical Source: NFPA 70, National Electrical Code, Table 310.15(B)(16-17) Conductor Sizing Always use the total length of the circuit for calculations.Ĭonsult with an engineer if your application requires more complex calculations.
Note: It's recommended to check the ampacity of a wire after doing a voltage drop calculation. It is recommended not to exceed a voltageĭistance - Enter the one-way length of the wires in the circuit in feet. Voltage Drop - Choose the maximum percentage of the source voltage drop. In a cable, burried in the Earth, or in open air. This is typically in a raceway (cable-tray or conduit), Installation - Choose the installation method for the circuit. Common conductors are copper and aluminum. Insulation - Select the thermal rating of the insulation on the wire.Ĭonductor - Choose the material used as a conductor in the wire. To calculate ground wire size, use the Ground Wire Size Calculator. For three-phase circuits, four wires are required. Single-phase circuits, three wires are required. This is typically single-phase or three-phase. Phases - Select the number of phases in the circuit.
To multiply the nameplate FLA by 1.25 for wire sizing. While three-phase voltages are typically 208V, 230V or 480V.Īmperes - Enter the maximum current in amps that will flow through the circuit. Single-phase voltages are usually 115V or 120V, The trouble with Copper is it will have corrosion/thermal issues with the lugs.Voltage - Enter the voltage at the source of the circuit. Large wires are expected to be aluminum because copper is rather expensive. That is due to dissimilar metals corrosion and thermal (expansion) issues copper lugs do not like aluminum. You may have heard the bad press about copper and aluminum wiring interacting badly and starting house fires. (Unless you really want 120-only or 240-only, but you don't.) In any case, you must still use outdoor rated cable, so SER is out of the question. Otherwise the pull can be rather difficult with heavy conductors. When laying out conduit, make sure to put pulling points in as many corners as possible. Generally multiconductor cable is less desirable in conduit because it is difficult to wield. Since the entire route is conduit, you want to run this in single-conductor THWN wire.
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