I agree with my electrician buddy the good Dusty man (I think). Its a bit hard to tell from the picture, but it looks like the Equipment GroundING Conductor (the bare No 4 copper) is bonded to the metal case/frame of the disconnect, while the Neutral is on an insulated black plastic block, therefore NOT bonded to the metallic case and subsequently also NOT bonded to the Equipment GroundING Conductor. HOWEVER if that black plastic block does indeed have the Neutral to the case frame disregard the prior sentence, I JUST CANT TELL FROM THE PICTURE.
That being said and that I cant tell whats what from the picture, HERES WHAT NEEDS TO BE DONE::::
The Neutral Grounded Conductor needs to be attached to a GroundING Electrode Conductor (like No 4 bare copper wire) that leads to a GroundING Electrode such as a driven rod or rods subject to local authority requirements. TO DO THAT ITS LIKE DUSTY SAID I think, install a jumper so as to wire that No 4 bare copper also to the Neutral, that way the Neutral is bonded to the grounding Electrode Conductor which leads to a GroundING Electrode (driven rod or rods).
In addition, the conductive metal case/frame of the disconnect (just like conductive non current carrying metal boxes like junction boxes etc) needs to be attached to the Equipment GroundING Conductor/Buss. If a jumper is ran from the small terminal up to the Neutral (what I think Dusty meant??) that will accomplish all the above: The Neutral will then be bonded to the Equipment GroundING Conductor (No 4 bare copper) which leads to an Equipment Grounding Electrode (driven rod or rods) and also the metallic case/frame of the disconnect is grounded yayyyyyyyyyyyyyyy
I (nor anyone here) can speak for local authority, but if they drove a ground rod and to it that No 4 bare copper wire (GroundING Electrode Conductor) is attached, Id say that will suffice for a proper GroundING Electrode. IE no more GroundING Electrodes are required.
Now that you have single point grounding at the first means of disconnection, from that points I agree I would run 5 wires, 3 Hots, Neutral GrounDED Conductor, and an Equipment GroundING Conductor.
NOTE AND CAVEAT: Is the service 208Y 120 Volt Three Phase Four Wire????????? Or 120/240 Volt Three Phase Four Wire Center Tapped (Red Leg) Delta??????????? THAT MAKES A BIG DIFFERENCE. If its a center tapped red leg delta, its 120 from 2 legs to neutral but 208 from the red/high leg to neutral
NOTE Perhaps that center red taped leg is the red/high leg????????????? IF SO BE CAREFUL and remember that's 208 to Neutral while its 120 from either of the other legs to Neutral !!!!!!!!!!!!!!
KEEP NOTE OF SUCH AS YOU RUN TO SUBS KEEP THAT RED/HIGH LEG IDENTIFIED
Sorry I cant tell from the picture whats what so this may all be wrong as rain NO WARRANTY
DISCLAIMER, This is merely an opinion, and like any opinions here, regardless if it agrees with mine or not, may be right and it may be wrong, Im NOT saying one way or the other, take it or leave it.
John T (suspect its a red/high leg delta so be aware and careful)