The call came in September 2022. Dana, an electrical contractor I had worked with for about three years, was standing in the lobby of a boutique hotel in Austin and she sounded stressed. 'The lighting designer quit. The chandeliers arrive Thursday. There are 12 glass dome fixtures stuck to the ceiling, and the owner wants them saved. Where do we even start?'
I'm an application engineer at Focal Point. I have spent roughly eight years helping commercial clients choose luminaires, lenses, and the right mounting position for both. I also keep a mistake log, and I've learned that the fastest way to help someone is to tell them about my own messes before they make the same ones.
Removing the Glass Dome Fixtures First
The question wasn't whether Dana's crew could install a chandelier. That part was mechanical. The real test came first: how to remove a glass dome light fixture without turning a $100 piece of glass into confetti. Glass dome ceiling fixtures from the 1990s look simple, but they are not all attached the same way.
I found that out in 2017, my first year in the industry. I told a maintenance manager he could just twist the dome counter-clockwise. It turned out to be a push-and-turn bayonet mount. The glass cracked before we got it off. Replacement cost was $108 plus a one-week wait, and the property manager still remembers my name for the wrong reason.
Here is the process we used for all 12 domes at the hotel:
- Turn off the circuit at the breaker panel, not just the wall switch, and confirm with a non-contact voltage tester. Fixtures with glass domes are often on the same circuit as other ceiling outlets.
- Support the glass dome with one flat palm before loosening anything. A 12-inch glass dome is heavier than it looks, and the center nut is usually the only thing holding it.
- Remove the center cap or decorative nut slowly. If it resists, stop. Old fixtures sometimes have a threaded collar instead of a nut, and forcing it can spin the whole fixture base.
- Lower the dome straight down. Do not tilt it. Tilting makes the edge catch on the trim ring, and that is how hairline cracks happen.
It sounds basic, but the reason I document this now is that every single dome on that job had a different mounting detail. Dana's crew saved all 12. That felt like a small victory until the next problem showed up.
Chandelier Placement Is About the Space Below, Not the Ceiling Center
With the old fixtures down, Dana stood in the middle of the lobby and asked where the three new chandeliers should go. Her original plan, which came from the previous designer, was simple: center each chandelier on the ceiling grid above each seating area. Seemed fine on paper. In reality, the first proposed location would have hung the chandelier directly in the sightline between the reception desk and the elevator lobby.
People tend to think of chandeliers as ceiling decorations. In commercial spaces, chandelier placement is really about the furniture and the walking path below it. We moved all three chandeliers before hanging anything.
For the lobby seating clusters, we used round tables about 60 inches wide. A chandelier over a table should be roughly half to two-thirds of the table width, so we specified 36- to 40-inch chandeliers rather than one massive statement piece. We hung the bottoms 30 to 36 inches above the table surfaces.
For the larger atrium area, where there was no table underneath, we hung the chandelier higher and treated the room itself as the scale reference. A common commercial guideline is to add the room length and width in feet and use that number in inches as a starting diameter. In that part of the lobby, roughly 30 by 40 feet, a 40- to 48-inch chandelier looked proportionate without dominating the space.
Also, if you are going to install a chandelier in a commercial setting, check the ceiling structure before you commit to a location. One of ours weighed 68 pounds. In the U.S., the ceiling box has to support the fixture weight—NEC Article 314 is where most inspectors start—and chandeliers over 50 pounds often need independent support. Dana's crew opened the ceiling and added a support wire before we hung anything. It added half a day and saved us from a call later.
The Lesson Hiding Inside the Phrase 'Focal Point'
The chandeliers went up without much drama. The real headache showed up when Dana turned on the accent lights that were supposed to highlight art near the check-in wall. Instead of crisp pools of light, the wall looked like someone had aimed six flashlights through a shower curtain.
Dana called me in. 'The spec said 18 degrees,' she said. 'These look like 50 degrees.' The fixtures were a generic recessed housing from a supply house, fitted with Focal Point lenses that Dana had sourced separately. The LED driver was fine. The modules were fine. The lenses were the correct part number.
Then I measured the distance between the LED die and the lens. That is where the phrase focal point stops being just a brand name.
A converging lens—the kind used in accent and spotlight optics—creates a controlled beam only when the light source sits at the right distance. In optics language, the LED chip is the object. When the object is at the lens focal point, the emerging rays are roughly parallel, which gives you a narrow beam. But when the object moves closer, inside the focal point, the rays do not straighten out enough. They keep diverging.
If you search for 'converging lens object inside focal point,' you will find textbook diagrams showing a virtual, upright, magnified image. That is not just a homework problem. In an LED accent light, it is exactly what turns an 18-degree spotlight into a soft wall wash. The lens was getting light, but it was not getting the light at the position it needed.
Dana's housing left only about 6 millimeters between the LED surface and the back of the lens. Our optic was designed for about 15 millimeters. The chip was sitting well inside the focal point, which meant the lens could not do its job.
The fix was not a different lens. It was a spacer ring that moved the lens out to the correct distance. We caught it before the client saw the full installation, so the cost was a few hours of labor and a small parts order. But it could easily have been a $3,200 redo if Dana had framed it differently.
While we were fixing that, Dana asked about something else she had read. 'What about a diverging lens inside the focal point? Does the same thing happen?'
Not exactly. A diverging lens, which is concave, spreads light out no matter where the object sits. If the object is inside the focal point, the image is still virtual, upright, and reduced. You never get a focused hotspot from a diverging lens. In commercial lighting, we use diverging optics when we want wide, even distribution—wall washers and some downlights—but never for a tight accent beam.
That distinction matters. A converging lens can give you a tight beam, but only if the source is not trapped inside its focal point. A diverging lens will give you spread, and the object position mostly shifts how even that spread is. Knowing which one you are holding is only half the battle. The source position is the other half.
What Went Into My Checklist After That Week
I don't tell this story because the physics is exotic. It isn't. The mistake was assuming that a lens part number guaranteed a beam angle. It doesn't. A lens is only one half of the optical system. The other half is where the light source sits relative to the focal point.
Now, every project that leaves our office gets a simple pre-install check. Confirm the distance from the LED package to the optical lens before promising a beam angle. If the object is inside the focal point of a converging lens, the beam angle stops being the number on the datasheet. Confirm chandelier placement against the furniture layout, not just the ceiling grid. And when removing glass dome fixtures, support the glass before you loosen anything.
I'm honestly still not sure why the previous designer had specified a fixture housing that was too shallow for the optic. My best guess is he chose the housing from an online cutsheet without checking the depth. That is a guess, not an accusation.
What Worked for This Hotel Might Not Work for You
I want to be honest about one thing: the hotel had generous ceiling heights and open space above the lobby, which made the chandeliers and the lens adapters straightforward. If your building has 9-foot ceilings or shallow plenums, the solution may look different. A chandelier needs vertical breathing room, and an accent optic needs a housing that can physically hold it at the right height. In tight spaces, a surface-mount fixture with an integrated LED board and lens might be the better answer.
This project worked because Dana called before the wall was closed up and before the chandeliers were wired to the wrong junction boxes. If you are working on something similar, measure the optics location, measure the ceiling height, and support the glass before you twist it. The physics is not negotiable, but the mistakes are optional.