I was wondering if anyone could explain the need for a four wire feed to a separate building apart from the house. In the case of the house I looked at today there was a separate garage with a subpanel fed by a three wire overhead feed. The grounds and neutrals were separate. To my knowledge there wasn’t any water or gas line going out to the garage. This should be a four wire feed, correct? And wasn’t this a relatively recent change to the code?
Thank you as always.