What does it mean when I find buried yellow "CAUTION" tape when digging a hole in the yard?.What is a reliable way to tell if the electrical service is 3 phase or single phase?.What is the minimum clearance of overhead electric service drop wires above a house roof?.What are typical copper service entrance wire/cable sizes for the electrical service to a house?.What is the fireman’s switch emergency disconnect requirement for residential electrical service?.Why is a leaning electrical service mast dangerous?.What is the minimum overhead electric service drop height/clearance to a house?.Here’s links with answers to some Frequently Asked Questions (FAQ) about ELECTRICAL SERVICE: Go to our articles What is a service conductor?and What is a feeder conductor? for the difference between the two. These sizes for service conductors also apply to feeder conductors. Electricians and experienced inspectors can tell at a glance if the service cable size is correct most of the time.įor sizes of aluminum service entrance cables, see our blog post What are typical aluminum service entrance wire/cable sizes for the electrical service to a house? But not all cables are clearly marked and sometimes the lettering strip is just not visible. Wire size may be marked on the side of the cable, followed by the letters “AWG”. The correct sizing of the neutral depends on doing a calculation of the “unbalanced load,” which is an estimate of the amount of 120-volt current usage. The neutral wire is often one or two sizes smaller than the two hots. An often-used rule-of-thumb is to jump up one wire size for each 100 feet of a long run. Wire sizes are AWG (American Wire Gauge), and adjustments may be necessary due to temperature rating or length of wire run. If you are unsure, seek the help of a licensed electrician.Here’s a listing of the standard copper service entrance wire sizes for residential 3-wire single-phase service. Always make sure to shut off the power higher up the line when working on a service panel. ConclusionĬhoosing the appropriate wire size for your 100 amp breaker is not as complicated as it seems. However, if you choose too small a gauge, the circuits will go bad and as a result, the risk of electrical fire will go up. Using the larger gauge will require you to spend more. Opting to err on the side of caution is the best idea here. When choosing between two gauge sizes for a 100 amp main breaker, you should know that bigger is always better. The heat-resistant and corrosion-resistant properties make it the most preferred wire material. It also uses less insulation and has a lower wire gauge compared to aluminum. On the other hand, copper has better conductivity and can handle higher electrical loads. Another drawback is the antioxidant coating required to resist corrosion, unlike the copper-clad aluminum. However, due to lower conductivity compared to copper, aluminum wiring needs a larger-sized wire. Aluminum wires are widely used because they are inexpensive, light, and flexible. Once you have figured out the wire size required, the next problem is choosing the wire material. It applies regardless of whether it is a breaker or subpanel.’ Copper vs Aluminum
If you consider the material, then the recommended gauge is 1 made of aluminum and 3 made of copper for a 100 amp branch circuit. The #3 AWG wire has 100A ampacity but it is supposed to be used in circuits requiring 80 amps or less. Therefore, #1 AWG has 130A ampacity which conducts at most 104 amps. It is a safety measure that tells you about the actual ampacity. The 80% rule of NEC says that the maximum loading for any branch circuit is 80% of the rating of the circuit for ampacity of wire for any load. However, the most appropriate one here is the #1 AWG wire with a 130 amp median capacity. From the wire gauge chart, we see that a #3 AWG wire seems to be the most plausible wire size with 100-ampacity.
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