I think I understand 250.24(B), but I have a situation where a feeder is run to a sub-panel (from the main service) and no grounded (neutral) conductor was run because the load is 240-volt and does not require a neutral. The sub-panel, however has extra breaker spaces in it. What does the NEC say about this? Does the grounded conductor need to be extended to this sub-panel for future 120-volt circuits? Would it make a difference if it were just a 2-pole disconnect (without extra breaker spaces)? Thanks for your help - Paul.