It is extended to all uses for greater safety, since
flame-resistant cables are now available from many
manufacturers.)
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2.1.3.1
Material for Conductors
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NOTE: If aluminum is to be specified for any of the
wire purchased, revise this paragraph accordingly.
Conductors for wire and cable rated 2,000 volts or
less shall be copper. For wire and cable rated
2,001 volts and above, the specifications may be
written to permit either aluminum or copper
conductors where aluminum is suitable for the
application and is determined to be more economical
than copper.
Aluminum conductors should be permitted only where
cost comparisons show an overall savings and after a
careful evaluation of the corrosion problems
associated with their use. They should only be
allowed where installers are qualified to make
reliable connections with them. Costs should be
compared between all pertinent items such as
installation, conduit, tray, tunnel and duct banks,
lifetime costs of energy losses if significant, and
differences in ventilation needs if losses are
evaluated. Conductors should have the required
current carrying capacities, the required short
circuit capacities, and should be satisfactory with
respect to voltage drop. Aluminum conductors should
be sized to have equal or less resistance than the
alternate copper conductors unless the total cost
comparison, including losses, shows a net advantage
otherwise. In such cases where the engineering
costs to properly compare the use of the two
materials will exceed any possible savings to be
achieved by aluminum, the arbitrary choice of copper
may be the best policy.
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Conductors shall conform to all the applicable requirements of NEMA WC 70,
as applicable, and shall be annealed copper. Copper conductors may be
bare, or tin- or lead-alloy-coated, if required by the type of insulation
used.
2.1.3.2
Size
Minimum wire size shall be No. 12 AWG for power and lighting circuits; No.
10 AWG for current transformer secondary circuits; No. 14 AWG for potential
transformer, relaying, and control circuits; No. 16 AWG for annunciator
circuits; and No. 19 AWG for alarm circuits. Minimum wire sizes for rated
circuit voltages of 2,001 volts and above shall not be less than those
listed for the applicable voltage in NEMA WC 70, as applicable.
SECTION 16120A
Page 10
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