Primary audience: Contractors
Start with the floor plan and mounting height
A high bay serves a task below it, not an empty rectangle on a drawing. Mark rack rows, picking stations, loading areas and open circulation paths first. Record the height from the fixture to each task plane, including vertical labels on shelving. Ceiling height and mounting height may differ when fixtures hang below beams or services.
Round UFO housings can suit open areas where light needs to spread around a mounting point. A linear fixture with aisle optics can direct light along rack rows. These are starting choices, not rules based on shape. A linear housing with broad optics may behave differently from the aisle version of the same model.
There is no universal ceiling-height boundary that selects UFO instead of linear. At greater mounting heights, the designer must check intensity, spacing and the amount of light reaching the task. At lower heights, glare and excessive brightness near a fixture may become the limiting factors. Ask for a layout using the actual mounting height before selecting output.
Compare the published high-bay options
Our UHB26 UFO, MLH06 linear high bays and FLS21 linear high bay have separate product pages. Compare their optic descriptions alongside the model tables. The MLH06 pages publish prismatic, aisle and narrow optics; selecting that family does not by itself select one of those distributions.
| Project condition | Compare first | Check before ordering |
|---|---|---|
| Open storage floor | UFO and broad-distribution linear fixtures | Overlap, perimeter coverage and glare |
| Long racking aisles | Linear fixtures with aisle optics | Rack-face illumination and optic orientation |
| Obstructed ceiling | Both shapes at feasible mounting points | Shadows, service access and support |
| Changing layout | Documented selectable-output models | Whether a revised layout still works |
Do not read the table as an installation specification. The same warehouse can need several distributions. Keep each selected optic, output setting and mounting method on the fixture schedule. For an overview of the spaces served, see warehouse LED lighting.
Use fixture lumens without losing the conditions
Watts describe electrical input, while lumens describe light output. Neither tells you how much illumination reaches a rack label. Two fixtures with similar lumen output can produce different patterns on the floor because their optics distribute that output differently. A brighter centre does not establish acceptable minimum illumination between fixtures.
Read each product table at the intended wattage and colour-temperature setting. Keep a maximum lumen value attached to the model and conditions that produce it. Do not pair the maximum output of one configuration with the lowest power setting of another. Where the page gives separate colour-temperature output columns, preserve that distinction in the comparison.
Use the warehouse lumen method to estimate an initial quantity. Work through that estimate with the high bay calculator. Then ask your designer to model that quantity with the correct IES file and room geometry. Review average illumination, the darkest points, rack-face light and glare together. Increasing wattage may raise the average while leaving a shadow behind a beam or rack unchanged.
Resolve voltage, mounting and controls together
Check the circuit before approving the fixture schedule. The 347 V and 480 V fixture directory lists the models whose published tables show those input options. A voltage option on MLH06 is not evidence for the same option on UHB26 or FLS21. The order must identify the required driver version.
Mounting also affects the comparison. FLS21’s page describes two chains with S-hooks. MLH06 lists mounting accessories separately. Confirm which hardware is included, which is optional, and which support method the project permits. Leave enough access to service the driver and controls without dismantling adjacent equipment.
For occupancy control, map detection to the working aisle rather than simply choosing a sensor by name. Ask about mounting height, detection coverage, time delay and the required behaviour when the aisle is vacant. Coordinate emergency operation separately. A normal-lighting sensor setting cannot establish the performance of an emergency circuit or battery accessory. Record the selected accessories beside the fixture, not in an undifferentiated note for the whole building.
Build a comparison the purchasing team can use
Send a marked floor plan, mounting heights, rack heights, supply voltage and the work performed in each area. Include existing fixture positions if the project must reuse them. Identify locations where access is restricted or where a new mounting point would interrupt operations. These constraints can matter more than the housing shape.
Ask for a comparison at the same maintained lighting objective. A proposal with fewer fixtures is not comparable if it omits rack faces or uses a different light-loss assumption. Request the calculation plane, reflectance assumptions, output setting and maintenance factors with each layout. Keep the luminaire schedule and calculation report together during review.
For a sample installation, choose a representative aisle or work area and inspect it during normal operations. Record the selected settings and observations from the people using the space. A sample helps assess visibility and controls, but it does not replace the complete layout. Send the resulting requirements through RFQ so the quotation refers to the same configuration the team reviewed.
Document checklist for the handoff:
- Drawing with mounting heights, aisle widths, racks and the working surfaces.
- Fixture schedule with exact model, optic, input option and selected output.
- Matched IES file, installation instructions and mounting-accessory list.
- Controls narrative, sensor coverage information and commissioning responsibility.
Related guides
- High Bay Mounting Height: Output, Optics and Task Planes
- Warehouse Lighting: Lumens, Foot-Candles and Fixture Count
- Gymnasium Lighting: Glare, Court Layout and Controls
Prepare the contractor fixture schedule.
Browse all buyer guides or send your fixture schedule for a quote.
Follow NEC/local code and use a licensed electrician.