Ernie- Some Panel have a need for a neutral for the indicator lights and some don't. As for a neutral buss, I can't say for sure. I look at a lot of Generac set up and they come with a harness that only contains one neutral of a small gauge wire. I don't believe it is the neutral for all the circuits in the harness. You can bet the farm I'll be watching for it on the next one.
I'm thinking too of all the switch loops out there that don't contain a neutral so I guess if a piece of equipment does not have a neutral buss, and if it's Listed I'd look at the Manufacturers Specs as an installer or as an Inspector.
