Lighting Power Density Verification in a Warehouse With High-Bay LED Retrofit
A 60,000 ft² warehouse (40,000 ft² storage, 20,000 ft² office) undergoes a lighting alteration: all high-bay fixtures in storage are replaced with LED high-bays, and office troffers are replaced with LED panels. The contractor submits a lighting power density (LPD) calculation showing 0.55 W/ft² for storage and 0.90 W/ft² for office, using the space-by-space method. The plans show 300 high-bays at 150 W each and 400 office panels at 30 W each. The jurisdiction uses the space-by-space LPD limits. During inspection, the inspector counts 320 high-bays installed and finds 40 additional office panels added in a corridor not shown on the lighting plan.
1. Recompute the as-installed LPD for each space and determine compliance, showing your method.
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Compute connected lighting power per space and divide by space area.
Storage: 320 × 150 W = 48,000 W. Area 40,000 ft² → 48,000/40,000 = 1.20 W/ft². Compare to the code's space-by-space LPD limit for storage/warehouse (the permitted value must be looked up in the adopted table; the contractor's claimed 0.55 W/ft² is the design figure, not the limit). The as-installed value is more than double the design basis and likely exceeds the limit - noncompliant.
Office: 400 × 30 W = 12,000 W (plus the 40 unplanned corridor panels if counted as office). 12,000/20,000 = 0.60 W/ft² for the planned panels; adding 40 × 30 W = 1,200 W gives 13,200 W → 0.66 W/ft².
Corridor panels: must be assigned to the correct space type (corridor) and its own LPD limit; they cannot be silently absorbed into office LPD.
The inspector should require a corrected space-by-space calculation using as-installed counts and wattages, not the design plan.
2. What code-compliance issues arise from the 40 unplanned corridor panels, beyond the LPD number?
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Several independent issues:
- Unpermitted scope change: fixtures not on the approved lighting plan mean the approved compliance documentation no longer describes the building; a revised lighting plan and LPD calculation are required.
- Space-type assignment: corridor lighting has its own LPD limit and control requirements; the reviewer must confirm the corridor's LPD and that occupancy/vacancy controls appropriate to corridors are provided.
- Control compliance: added fixtures must be on compliant controls (occupancy sensors, time-switch, or as required for the space type); uncontrolled added fixtures fail the lighting controls provisions even if LPD passes.
- Alteration threshold: the added fixtures may push the alteration past the threshold that requires the whole lighting system to comply, rather than just the altered portion.
The inspector should document the discrepancy and withhold final lighting sign-off pending a revised, approved lighting plan.