Electrical Calculations for Code Exams

What you'll learn

• Apply Ohm's law, the power equations, efficiency and power factor to find currents, resistances, power and energy, and check answers for units, size and direction.
• Calculate voltages and line currents in 120/240 V single-phase and 120/208 V and 347/600 V three-phase systems, including balanced loads and wye neutral currents.
• Calculate the load for a single dwelling under Rule 8-200, including living area, heating, air conditioning, the range, full-value loads, other large loads and the minimum.
• Calculate per-unit loads and combined service loads for apartments, row housing and houses with secondary suites using the stepped demand factors of Rule 8-202.
• Apply the floor-area method of Rules 8-204 to 8-210 and Table 14 for schools, hospitals, hotels and other occupancies, and use Rule 8-106 for recorded demand and non-coincident loads.
• Select conductors from the Section 4 ampacity tables, applying ambient and bundling corrections, termination temperature limits and the continuous-load rule.
• Calculate single-phase and three-phase voltage drop, size conductors for long runs within the limits of Rule 8-102, and use the Appendix D tables.
• Check box fill under Rule 12-3034 and conduit fill with the conductor and raceway area tables and the fill limits.
• Choose transformer ratings, calculate rated currents, and apply Rules 26-254 and 26-256 for overcurrent protection and conductors, including secondary fault current.
• Size motor branch circuit conductors, feeders, short-circuit protection, overload protection and disconnecting means under Section 28.
• Work complete service and feeder sizing problems from demand load to equipment ratings, including managed EV loads and neutral sizing.
• Solve mixed calculation questions under exam conditions using a consistent layout, without reproducing Code tables, by looking up every value in the 2024 CE Code.