One traction elevator's motor power from its rated load, speed, and counterweight balance, then the NEC Table 620.14 demand factor that lets a shared four-elevator feeder be sized well below the sum of all four running flat-out.
| Rated load per car | 1000 kg |
| Rated speed | 1.5 m/s |
| Counterweight balance factor | 0.5 (50% of rated load balanced) |
| Drive efficiency (mechanical x motor) | 0.7 |
| Number of identical elevators on the shared feeder | 4 |
| Feeder voltage / power factor | 415 V 3-phase / 0.85 |
The counterweight balances a fraction of the rated load — the motor only has to move the remaining unbalanced portion at rated speed.
Table 620.14 reflects the reality that not every elevator in a group runs at full duty simultaneously — the demand factor drops as more elevators share a feeder.
| Check | Requirement | Actual | Status |
|---|---|---|---|
| Single unit motor power | n/a (sizing basis) | 10.51 kW | ✓ PASS |
| Connected load (4 units, no diversity) | n/a (informational) | 42.04 kW | ✓ PASS |
| NEC 620.14 demand factor (n=4) | n/a (code table lookup) | 0.85 | ✓ PASS |
| Feeder demand load | n/a (sizing basis) | 35.74 kW / 58.49 A | ✓ PASS |
Key insight: NEC 620.14's demand factor exists because elevator group operation is inherently non-simultaneous by design — a dispatch system rarely runs every car in a bank at full duty at the same instant, so sizing the shared feeder for 100% connected load on every unit would be a real but avoidable oversizing. The demand factor gets smaller as more elevators share a feeder (down to 0.72 for 10 or more), reflecting that duty-cycle overlap becomes statistically less likely to hit 100% concurrently as the group grows.
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Open Elevator Electrical Demand calculator →Only to the shared feeder — each individual elevator's own branch circuit and motor protection still has to be sized for that elevator's own full-load current with no diversity applied, since any single car can and does run at full duty at any moment. The demand factor is specifically a feeder-level allowance for the statistical unlikelihood of every car in the group being at full duty at exactly the same instant.
The counterweight's whole purpose is to offset most of the car's weight so the motor only has to supply the net difference — a higher balance factor (closer to 1.0) leaves less unbalanced load for the motor to lift, directly reducing both motor power and current, though in practice the balance factor is chosen based on expected average passenger loading, not maximized purely to minimize motor size.