Lighting circuit load equations
Fixture input watts and driver power factor determine steady VA and current; inrush is screened separately.
P = Pfixture × NS = P/PFI = S/VNcircuits = ceil(I/(In × Fload))Iinrush = Ifixture,inrush × N × Fsimwhere:
- S
- Lighting apparent power[VA]
- In
- Breaker rated current[A]
Use the driver manufacturer's protective-device compatibility table for final circuit quantity.
How to use the Lighting Circuit Load Calculator
Calculate connected lighting watts, input VA, current, energy, circuit quantity, loading per circuit, and LED driver inrush screening. Start by choosing the operating mode, then enter values from nameplates, measurements, or project documents in the units shown. The result updates immediately and keeps intermediate quantities visible for review.
- Confirm the system and calculation mode.
- Enter measured or manufacturer-rated values.
- Review the primary result and intermediate metrics.
- Continue with the related protection or equipment-selection checks.
Calculation method and validation
The equations and symbol definitions above show the complete calculation basis. Inputs are checked before calculation so zero, negative, incompatible, or physically impossible combinations are flagged instead of silently producing a misleading result.
How to interpret the result
Use the main result as a starting value and read every supporting metric. Single-phase lighting circuits Entered watts are fixture input watts Steady power factor and simultaneous inrush factor A passing or recommended result means the entered mathematical conditions are satisfied; it does not certify the complete installation or a particular product combination.
- Single-phase lighting circuits
- Entered watts are fixture input watts
- Steady power factor and simultaneous inrush factor
Selection limits and next checks
Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions. Breaker compatibility depends on the driver manufacturer's inrush duration and maximum devices per protective device. Verify conductor, voltage drop, harmonics, neutral loading, controls and emergency circuits. Compare the output with the current applicable standard, local rules, exact VIOX product datasheet, environmental conditions, protection coordination, and the engineer's project requirements before procurement or installation.
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Assumptions
- Single-phase lighting circuits
- Entered watts are fixture input watts
- Steady power factor and simultaneous inrush factor
Important Warnings
- Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions.
- Breaker compatibility depends on the driver manufacturer's inrush duration and maximum devices per protective device.
- Verify conductor, voltage drop, harmonics, neutral loading, controls and emergency circuits.