My residence main breaker is below the meter on the exterior of my detached garage. Feeders extend 50 feet through the attic and breezeway to my residence. The residence load center has a grounding rod and grounding terminals My main breaker disconnect and enclosure has no grounding. It would be convenient to tap my main breaker and on the other side of the garage wall add a breaker box for 220 welding service. Would it be safe to add a grounding rod for the new panel or do I need to run a bare to the house load center?