Can I substitute two 14-gauge wires together for one 10-gauge wire? Using it from the generator RB-30 remote box, to the transfer switch inside a 6', 10-3 whip in the basement.
If the installation needs to comply with US NEC, 310.4 forbids paralleling conductors smaller than 1/0 (with some limited exceptions that do not apply to the described installation.)
310.4 Conductors in Parallel
Aluminum, copper-clad aluminum, or copper conductors of size 1/0 AWG and larger, comprising each phase, polarity, neutral, or grounded circuit conductor shall be permitted to be connected in parallel (electrically joined at both ends).