Quote from link: "Section 310.4 provides specific information and requirements for paralleling of conductors and should certainly be the first reference that a user would choose for an understanding of the basics for paralleling conductors. The first paragraph in this section permits aluminum, copper-clad aluminum and copper conductors that are at least 1/0 AWG or larger to be connected in parallel if these parallel conductors are electrically joined at both ends to form a single conductor."
http://www.ecmag.com/section/systems/conductors-connected-parallelAt hand we are talking about #6 AWG.
