Sometimes, a breaker or fuse panel is required at some distance from the home’s main electrical service disconnect. That main disconnect may be a single OCPD at the service entry, or the “main” breaker panel. The downstream panel is called a “remote distribution panel”, what we commonly refer to as a “sub-panel.” It’s important to understand that any distribution panel downstream of the main service disconnect is a sub-panel. If the house has a service disconnect separate from the only breaker panel in the building, that sole breaker panel is still a sub-panel. If electricity is drawn off the only panel in the home to another panel, that other panel is a sub-panel, even if the “main” panel is also a sub-panel.
We are not just fussing over terms here! “Main” service panels and “sub-panels” are wired differently to prevent harmful electrical currents from developing where they shouldn’t be. This is accomplished by NOT connecting the “grounded” white neutral wires to the bare/green “grounding” wires in a sub-panel. Sub-panels should be fed by a 4-wire circuit: 2 hot wires (black and red), 1 white neutral, and a bare or green grounding conductor.
Sub-panels can have all of the same defects as “main” panels, and then some. For that reason, we will only cover defects specific to sub-panels here. Refer to the “Panel” section of Inspecto Libro for defects common to all distribution panels.
Service Panel wiring (main disconnect):
Sub-Panel wiring (note the unbonded neutral and 4-wire feed):
The sub-panel’s neutral wires are not isolated from ground. This is a safety hazard. Hire an electrician to make the required repairs.
