Up2Code— Your neutral only has to be large enough to carry the maximum calculated unbalance load between the neutral and any one ungrounded conductor. So if your storage units had a total load of 50a. and 30 of those amps were 240v. (figure 120/240v feeder) Then your neutral would only have to be rated 20a. But you have to be careful because your neutral can not be smaller than your Grounding Electrode Conductor if this is Service.
220.61(A), 250.24(C)(1)
