Panel Schedule Total Load Mismatch After Adding Motor Loads
A panel schedule for DP-2 shows a connected load of 148 kVA and a demand load of 112 kVA. After adding four 3-phase, 480V motor loads rated 25 hp each, the connected total rises but the demand total barely changes, and the panel's main breaker appears undersized when compared to the calculated demand. The project uses a demand factor of 1.0 for receptacles, 1.25 for the largest motor, and lighting demand per code. The engineer expected the demand to rise by roughly 75 kVA. A reviewer notes that one motor circuit shows a load classification of 'Other' rather than 'Motor'.
1. Diagnose why the demand total did not rise as expected and how load classifications affect the panel schedule totals.
Read the worked answer
Revit's panel schedule demand totals are driven by load classifications and the demand factors assigned to them in Electrical Settings. Each circuit's load is computed from the classification assigned to the connected elements. If a motor circuit carries the 'Other' classification, it uses that classification's demand factor, which may be 1.0 or lower, rather than the motor classification with the 1.25 factor applied to the largest motor.
That explains a muted demand increase: the connected load rises because kVA is added, but the demand calculation applies the wrong factor and, for the largest-motor adder, may not apply at all if no circuit is classified as Motor.
Fix: edit the load classification for each motor circuit to 'Motor', confirm the demand factor table assigns 1.25 to the largest motor, and re-check the panel schedule. Also verify the motor kVA is entered correctly (hp converted to kVA using efficiency and power factor, not hp directly), because a wrong apparent load will distort both totals.
2. The main breaker appears undersized against the demand. Explain how you would determine whether the breaker is actually inadequate, and what you would check before resizing.
Read the worked answer
First, confirm the demand calculation is correct after fixing classifications. Compare the corrected demand kVA to the main breaker rating converted to kVA at 480V three-phase.
Second, check whether the panel schedule is displaying demand at the panel level or circuit level, and whether spare and space circuits are included. A common error is comparing connected load to breaker rating rather than demand.
Third, verify the largest-motor adder is applied once, not per motor, and that continuous versus noncontinuous load factors are applied per code. Motor loads are typically continuous at 125%.
Fourth, check that the panel's supply is single-phase or three-phase as modeled; a phase imbalance can make one leg appear overloaded even when total demand is fine.
Only after these checks would I resize. If the corrected demand exceeds the breaker, upsize the main and verify the feeder and upstream distribution accommodate it. Document the before-and-after calculation.