Services, Service Equipment, and Panelboards
Service equipment
Service-entrance conductors run from the service point to the service disconnecting means. Know overhead service drop clearances, underground service lateral depths, service mast requirements, and the location of the service disconnect nearest the point of entry. Service equipment must be suitable for the available fault current and marked with its rating. The service disconnecting means may consist of up to six switches or breakers grouped in one location.
Panelboards and working space
Panelboards distribute power and must be accessible, not located in bathrooms or over stairs, and provided with dedicated working space. Working space is typically 30 inches wide, 36 inches deep, and 6½ feet high, with the depth increasing for live parts above 600 V. Know busbar ratings, neutral and ground terminations, and the requirement to keep the neutral isolated in subpanels.
Traps
Candidates confuse the service point, service drop, and service lateral, or assume a panelboard is service equipment without a listed rating. The six-disconnect rule is often misread as six per panel rather than six for the service. Do not ignore the requirement to group disconnects or to label the service disconnect.
Worked example
A 400 A service may use two 200 A service disconnects grouped at the point of entry, provided the total calculated load is served and the grounded conductor is bonded only at that location. Rule of thumb: count disconnects, not panels, and verify the working-space box before approving the layout.