"(1)
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All aluminum conductors must be at least No. 2 AWG. Any conductor
smaller than No. 2 AWG must be copper.
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"(2)
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For all single-family attached, single-family detached, and
multifamily dwelling units of fewer than 10 units per building, all
conductors and wiring shall be copper conductors. Conductors made
of any other material, including aluminum, shall not be permitted.
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"(3)
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For all other buildings, copper conductors must be used in the
following circumstances:
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"(a)
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For any conductor smaller than No. 2 AWG.
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"(b)
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For any branch circuit designed for less than 90 amps.
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"(c)
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For any vibrating equipment, any branch circuit between starters/disconnects
and motor loads, primary and secondary connections to transformers,
and for final connections.
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"(d)
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In residential uses, for any branch circuits coming from the
main overcurrent device for an individual residential unit."
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"(1)
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For use underground, including direct burial in the earth. For
underground requirements, see 300.5.
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"(2)
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As single-conductor cables. Where installed as single conductor
cables, all conductors of the feeder grounded conductor or branch
circuit, including the grounded conductor and equipment grounding
conductor, if any, shall be installed in accordance with 300.3.
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"(3)
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For wiring in wet, dry, or corrosive locations UF cable is not
allowed.
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"(4)
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Installed as nonmetallic-sheathed cable, UF cable is not allowed.
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"(5)
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For solar photovoltaic systems in accordance with 690.31.
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"(6)
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As single-conductor cables as the nonheating leads for heating
cables as provided in 424.43.
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"(7)
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Supported by cable trays. Type UF cable supported by cable trays
shall be of the multiconductor type.
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"Informational Note: See 310.15(A)(3) for temperature limitation
of conductors."
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