Estimates a traction elevator's motor power from its rated load, speed, counterweight balance factor and overall drive efficiency, then applies the NEC Table 620.14 feeder demand factor to size a shared feeder for a group of similar elevators — since not all elevators in a bank run simultaneously at full load.
Standards followed
NEC Table 620.14 (feeder demand factors, two or more elevators)Standard elevator-engineering motor power formula (mechanical power from net unbalanced load × speed, divided by drive efficiency)
What it can do
- Single-unit motor power from rated load, speed, counterweight balance factor (fraction of load offset by the counterweight) and overall efficiency.
- Approximate 3-phase full-load current from the computed power, voltage and power factor.
- Connected load for N identical elevators and the NEC Table 620.14 demand factor for that count (1.00 down to 0.72 for 10 or more).
- Demand load (kW and approximate FLA) after applying the demand factor.
Example problem
1000kg rated load, 1.5 m/s speed, 50% counterweight balance, 70% overall drive efficiency, 4 identical elevators on a shared 415V/0.85PF feeder.
- Net unbalanced load = 1000 × (1 − 0.50) = 500kg.
- Single-unit power = 500 × 9.81 × 1.5 / (1000 × 0.70) = 10.51kW.
- Connected load for 4 units = 10.51 × 4 = 42.04kW.
- NEC Table 620.14 demand factor for 4 elevators = 0.85.
- Demand load = 42.04 × 0.85 = 35.74kW.
10.51kW per unit, 42.04kW connected, 35.74kW after the NEC demand factor.
Want the full step-by-step version?
The motor power formula is a standard elevator-engineering estimate for preliminary electrical sizing — final sizing should use the actual elevator manufacturer's motor nameplate data. The demand factor table assumes all elevators on the feeder are of similar size; for mixed-size banks, engineering judgment is required. Escalators aren't covered here — they run continuously regardless of passenger load and are typically sized directly from the manufacturer's motor nameplate (see the Motor Calculator for branch-circuit/OCPD sizing from a known FLC).