The Canadian code has an interesting exception to the 1/0 rule:
Ungrounded and grounded circuit conductors of similar conductivity in sizes No. 1/0 AWG and larger,
copper or aluminum, shall be permitted to be installed in parallel sets provided that each parallel phase or
grounded conductor set is individually comprised of conductors that are
(a) free of splices throughout the total length;
(b) the same circular mil area;
(c) the same type of insulation;
(d) terminated in the same manner;
(e) the same conductor material; and
(f) the same length.
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(5) Conductors of similar conductivity in sizes smaller than No. 1/0 AWG copper shall be permitted in parallel
to supply control power to indicating instruments and devices, contactors, relays, solenoids, and similar
control devices, provided that
(a) they are contained within one cable;
(b) the ampacity of each individual conductor is sufficient to carry the entire load current shared by the
parallel conductors; and
(c) the overcurrent protection is such that the ampacity of each individual conductor will not be
exceeded if one or more of the parallel conductors becomes inadvertently disconnected.
Bill
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"Why not the best?"
Jimmy Carter