In my house's main panel, there is a big bus where the neutral wires and the ground wires are all bonded together (if memory serves). From what I understand, this is the only place the neutral wires and the ground wires can be connected (in the panel). Because the ground wire is not supposed to carry any current and all.
In the same main panel, there is a 40A 2-pole breaker which is hooked to 8 gauge wire which runs out to the detached garage's sub-panel. In the garage panel, all the neutral wires are connected together, and all the ground wires are bonded to the box, but the grounds/box and the neutrals are NOT bonded together, as far as I can tell. Is this correct/normal? I kind of expected the garage neutrals and grounds to be tied together since it's 'a breaker box'. I'm wiring a 4-wire 240V receptacle out there, and I'd like to correct things if I can.
Also, the 8-ga wire that feeds the garage panel appears to have a substantially smaller ground wire, like 12-guage, even though it looks like it's in a typical romex jacket with the other 8-ga wires. Was this allowed under older codes? I've never seen romex where the ground wire is smaller.