In article , dpb wrote:
AFAIK the arrangement is not condoned by NEC; where specifically it says
it except under the workmanship clause I've no idea since it's patently
silly as two wires of smaller size are more costly than the one larger.

Right he

"... conductors of size 1/0 AWG or larger ... shall be permitted to be
connected in parallel..." [2008 NEC, Article 310.4(A)]

Anything smaller than 1/0 AWG is not allowed to be run parallel.