I have a 5KV-480-208/120 dry type transformer manufactured by OLSUN -USA . The size of primary wires ( H1 , H2 , H3 ) and Secondary wires ( X0 , X1 , X2 , X3 ) is 14 AWG . The primary cable is 4C x 4 MM2 ( 12AWG ) and secondary cable is 4C x 35 MM2 ( 2AWG) . Both cables are XLPE/SWA/PVC . For terminations inside the transformer , Does NEC allow using wire nut or I can use terminal lugs with one hole with bolt and nuts with heat shrinkable tube , rubber tape and electrical tape . I could not find a manual on OSLUN website .