I bought a Cutler Hammer CHSPULTRA whole house surge protection device, which comes with 4 wires: two go to a 2-pole breaker, one that goes to the neutral bus bar and the fourth wire that is meant to go to the ground bus bar. My load center does not have a separate ground bus bar. Any idea if both wires can be wired to the neutral bus bar or do I need to have a separate ground bar installed? Cutler Hammer's website was no help. Thanks in advance for any suggestions.