UFO or linear: choosing a high bay fixture

Two fixtures can put the same number of lumens into a building and give you a different building to work in. High bay lighting is where that shows up most, because the fixture is a long way from the floor and the shape of what it throws matters as much as how much it throws.

What the two shapes do differently

A UFO high bay is round and compact. The Crater UFO housings are listed as Ø12.27.3 at 100W and 150W, and Ø14.67.9 at 200W and 240W. That compact form concentrates output beneath the fixture, which is what you want over open floor.

A linear high bay spreads its LEDs along a bar. The LTR-PHB08D-165 housing is listed as 2412.62.1, and it throws along its length — which is the shape of a racking aisle, not a square bay.

Output, side by side

Crater UFO LED High Bay, all at 5000K, AC100-277V, IP65 and 0-10V dimming:

• 100W — ~15500lm, replaces ~300W HID
• 150W — ~23000lm, replaces ~400W HID
• 200W — ~31000lm, replaces ~600W HID
• 240W — ~37200lm, replaces ~750W HID

Linear LED High Bay, LTR-PHB08D-165:

• 110W / 135W / 165W selectable in one housing
• 14000~20800lm across those settings
• 4000K or 5000K
• Dimmable, AC100-277V

The `Replaces` row on the Crater sheet is the useful one in a retrofit: it maps each LED wattage to the HID wattage it is meant to stand in for, so you can walk a building counting existing fixtures rather than starting from a photometric study.

Aisles versus open floor

The general practice is straightforward once you know the two distributions:

• Rows of racking, with the fixture running above and along the aisle — linear.
• Open floor, assembly areas, bays where people and equipment move in every direction — UFO.
• A building with both — both. There is no rule that a facility gets one fixture type, and mixing them along the same circuit is normal.

When neither is the answer

Two other fixtures in the catalogue cover the cases a high bay is wrong for:

• EZ-Mount Tri-Proof — a sealed linear fixture for wash-down areas, dust and damp: 30W to 120W, 3900lm to 15600lm, in lengths from 23.6 to 94.5 inches. This is the fixture for a machine shop, a food plant, a parking structure or a tunnel.
• LED Batten Light — 4ft at 30W (~3600lm) or 8ft at 60W (~7200lm), CRI >80, for lower mounting heights where a high bay would be overkill and glare.

Two things to check before you commit

Selectable wattage. The linear high bay's 110/135/165W selection means one part number covers three light levels. If the layout is not final, that is one less decision to lock in early.

The IES files. Both fixtures publish IES photometric files at 120V and 277V — the Crater UFO for several of its wattages, the linear high bay for LTR-PHB08D-165. Those are the files a lighting designer runs to model the space before anything is ordered, and they are on the product pages.