A subpanel, often referred to by homeowners as “another breaker box,” is a secondary electrical distribution center powered by a circuit from the main service panel. Ricardo Mitchell is the CEO of CN Coterie, a fully licensed and insured Lead EPA (Environmental Protection Agency) Certified construction company located in Manhattan, New York. It performs several central functions: Firstly, it. Your Practical Guide to Electrical System Upgrades Ever felt that jittery feeling when flipping a switch after upgrading your electrical system? Like your home's heartbeat suddenly got louder? Distribution boxes sit silently in our walls, humming the quiet tune of modern life. But when expansion. secondary unit substation is a close-coupled assembly consisting of enclosed primary high voltage equipment, three-phase power transformers, and enclosed secondary low-voltage equipment. The following electrical ratings are typical: As a result of locating power transformers and their close-coupled. Selecting a distribution box: number of groups and expansion options.