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What are typical aluminum service entrance wire/cable sizes for the electrical service to a house?
Sunday, June 17, 2018
Here’s a listing of the standard aluminum service entrance wire sizes for residential 3-wire single-phase service. Wire sizes are AWG (American Wire Gauge), and adjustments may be necessary due to temperature rating or length of wire run. An often-used rule-of-thumb is to jump up one wire size for each 100 feet of a long run.
SERVICE SIZE WIRE SIZE
100 amp #2
125 amp #1/0
150 amp #2/0
200 amp #4/0
225 amp #250
The neutral wire is often one or two sizes smaller than the two hots. 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.
Wire size may be marked on the side of the cable, followed by the letters “AWG,” like in the photo below. But not all cables are clearly marked and sometimes the lettering strip is just not visible. Electricians and experienced inspectors can tell at a glance if the service cable size is correct most of the time.
Aluminum wire sizes are usually one notch larger than copper for the same service rating. Also, the grey or black gooey stuff you will see around the aluminum wire lug connections is a required anti-oxidant paste.
The aluminum wire used for service cables and wiring for larger-amperage circuits in a home is multi-strand and a different metal composition that the solid aluminum wiring used during the early 1970s, that was later banned as a fire hazard.
For the sizing of copper service entrance cables, see our blog post What are typical copper service entrance wire/cable sizes for the electrical service to a house?
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