Commercial and agricultural LED lighting

Layout and beam angle decide it, not lumens

A lumen figure tells you how much light leaves the fixture. It says nothing about where that light lands, and where it lands is the whole job. Two 22,000 lumen high bays hung at the same height, one with a 60 degree optic and one with 120, give you two different buildings. The narrow one puts light down the aisle and onto the rack faces. The wide one washes the floor and the tops of the shelving while the aisles stay dim.

So the order of decisions is mounting height, then spacing, then beam angle, and fixture wattage comes last. A 30 foot deck wants narrower optics on wider spacing. An 18 foot deck with those same fixtures glares and leaves scallops of dark between them. Racking changes it again, because it blocks light from the side, and a layout drawn without the rack positions is a layout for an empty building.

The reasoning is worked through in choosing and spacing high bay fixtures, and what it looks like in a real building is in the warehouse high bay job.

A barn needs a different fixture than a warehouse

Ammonia is the first reason. In a poultry house or a bedded pack barn it attacks aluminium housings, creeps into the driver compartment and corrodes terminals from the inside. A high bay taken off a general commercial catalogue often lasts two or three years in that air and then starts failing one fixture at a time, which is the expensive way to find out.

Washdown is the second. Article 547 of the National Electrical Code requires luminaires in these buildings to keep out dust and moisture, to be watertight where the space is washed for sanitation, and to be guarded where they can be struck. In practice that means a sealed gasketed fixture with an ingress rating you can point at, not a linear strip with open end caps. The article is covered in plain language in what the code requires in a barn, and the wiring feeding those fixtures in choosing a wiring method for agricultural buildings.

The third difference is control. A broiler lighting program commonly runs 3 to 5 footcandles along the feeders during brood and dims down to a quarter footcandle or less by the end of the flock, which Mississippi State University Extension sets out fixture by fixture, and the dimmer has to be a trailing edge type. A TRIAC dimmer built for an incandescent bulb does not see an LED driver as the resistive load it expects, and the lights flicker or fail outright rather than dim smoothly. Dairy runs the opposite program: long day lighting holds 16 to 18 hours at 15 to 20 footcandles followed by 6 to 8 hours of near darkness, and Michigan State University Extension has documented herds gaining close to 10 percent more milk on that schedule. Both are in the free stall barn lighting job and the poultry house ventilation and power job.

The maintenance argument at height

The cost of a high bay is not the fixture. It is the lift, the aisle you clear to get the lift in, and two people working at 28 feet. That is true the first time and every time after, so fixtures should be chosen as though replacing one is expensive, because it is.

LEDs rarely fail the way lamps did. Drivers fail, and they fail early when they run hot or when they were the cheapest part of a cheap fixture. That is the argument for a product with a driver you can still buy in six years and a warranty covering labour, not just a box on a shelf. Where the schedule allows we do the work in blocks during a shutdown, as in plant wiring during a shutdown.