![]() Wires have insulating materials for different purposes. Aluminum wires are cheaper and lighter than copper, but they are less conductive and more brittle than copper. Copper wires are thinner and have better tensile strength than aluminum, but they are more expensive. ![]() Choose the right materialĬhoose the material that’s right for your budget and needs. Using thicker wires can prevent voltage drop in longer wires, so expect to use thicker conductors for a service connection 400 ft away than at 250 feet. Voltage drop increases as the wire gets longer. A thicker wire with a higher ampacity can reduce the chance of damaging the insulation.Īside from ampacity, another factor to get the right size of wire for amps we need is the voltage drop. ![]() When resistance increases due to the higher current, more heat is released that might eventually damage wire insulation. Some wire insulations are more tolerant of higher temperatures than others. Of course, the conductors need to be thicker to accommodate this setup. The confined space raises the wire’s operating temperature and causes more resistance. When a wire is in free air, heat from the wires can be easily dissipated unlike in a conduit or in a bundle. Wire installationĪ wire installed in free air will have higher ampacity than a wire installed in a conduit or a bundle. Aluminum is less conductive than copper, so aluminum wires need to be thicker to deliver the same amount of current that copper wires can. Some materials are better conductors than others. Several factors can affect the rating of a wire, so the wire size might be adjusted to meet the required current. The proper wire size should at least have an ampacity that meets your service requirements. Thicker wires can carry more current and are rated with a higher ampacity. The main factor that affects wire sizing is the wire’s ampacity. Consult a licensed electrician when installing service conductors. Take note that an electrician can give you a more detailed recommendation based on both your needs and the local code in your area. The most appropriate aluminum wire size will be 1/0 gauge with an impedance of 0.20. \įinally, we look at a resistance chart to find the conductor size that suits the impedance that we need. If the service uses aluminum wires at 240 volts, then the 5% voltage drop will be: If we want to know the underground wire size for a 100 amp service conductor that’s 300 feet away, let’s determine the voltage drop first. For this, we will take a 5% voltage drop limit, similar to the maximum voltage drop of feeders and branch circuits combined. Technically, the NEC has no requirement for the voltage drop for service conductors. NEC Section 310.12(A) might be fine at 50 feet but become insufficient at 150 feet and 300 feet. Voltage drops can affect the performance of appliances and shorten their lifespan. ![]() Aside from ampacity, voltage drops should also be considered when planning a long service wire, especially at 300 feet. ![]()
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