Look, I'm not going to tell you I'm a lighting expert. I'm just the guy who's been handling commercial lighting orders for about 7 years, and I've personally made (and documented) about 15 significant mistakes totaling roughly $1,200 in wasted budget.
That's $1,200 I had to explain to my boss. Not fun.
Most of those mistakes happened when I was rushing or when I assumed I knew what I was doing. After the third rejection in Q1 2024, I created our team's pre-check list. We've caught 47 potential errors using this checklist in the past 18 months.
This article covers three specific areas where I see people make the same mistakes I did: recessed lighting positioning, linear system specs, and tube type selection (especially Type A LED tubes). If you're ordering for an office or a small commercial project, this list is for you.
Mistake #1: Treating Recessed Lighting Like Any Other Downlight
In my first year (2017), I made the classic mistake with recessed lighting. I specified what I thought was a standard downlight for a drop ceiling in a meeting room. Looked fine on my screen. The result came back: 18 recessed fixtures, all sitting too high in the ceiling, creating dark rings on the ceiling surface.
18 items, about $680, straight to the trash.
Here's what I learned:
Step 1: Always Check the Trim Type
Recessed lighting isn't just about the can or the housing. The trim determines how the light interacts with the ceiling. If you're using a baffle trim in a ceiling with thick tiles, you'll get a shadow. If you use a reflector trim in a room with low ceiling height, you'll get glare.
My checklist now says: Confirm trim type matches ceiling material and height.
Step 2: Measure the Ceiling Cavity Depth
Most recessed housings need a certain depth behind the ceiling. If your ceiling tile rests on a grid, you might only have 4 inches of space. Some IC-rated housings need 6 inches.
I once ordered 24 housings for a retrofit project where the ceiling cavity was only 3.5 inches deep. Every single one had to be returned. That was a painful lesson.
So glad I now measure before ordering. Almost skipped that step to save 15 minutes, which would have meant another expensive return.
Step 3: Verify the Focal Point of the Trim + Bulb Combination
Here's something most people don't think about: the focal point of a concave lens (in this case, the trim's internal shape) determines how the light spreads. A deep baffle will focus the light differently than a shallow reflector. If you're using a lensed trim, the focal point of the concave lens is critical for getting the right beam angle.
I still kick myself for not checking this on a conference room install. The trim we used shifted the focal point upward, creating a hotspot on the ceiling instead of on the table. If I'd checked the spec sheet instead of assuming, we'd have avoided the 1-week delay for replacement parts.
Mistake #2: Ignoring the 'Diverging Lens Inside Focal Point' Effect in Linear Systems
This sounds technical, but it's simple: when you have a lens (like an acrylic cover on a linear fixture) that sits inside the focal point of the light source, it acts as a diverging lens. The light spreads wider than intended.
I once ordered 60 feet of linear lighting for a retail display. The spec sheet said the beam angle was 60 degrees. But the lens we chose (a diffusing acrylic) sat just a few millimeters inside the focal point of the LED chips. The actual beam angle? Closer to 90 degrees.
The effect on the display? Washed-out colors and shadows in places we didn't want. $450 wasted + the embarrassment of explaining to the client why the lighting didn't match the mockup.
Why does this matter? Because a diverging lens inside focal point position can ruin your light distribution. Here's the checklist item:
- Check the lens-to-LED distance vs. the chip's focal length. If the lens sits inside that focal length, treat it as a diverging lens. Expect wider spread and lower intensity at the center.
- For linear systems in display applications, use a lens that sits at or beyond the focal point. This ensures the lens acts as a converging or neutral element—not a diverging one.
I recommend this for uniform ambient lighting, but if you're dealing with accent or task lighting where precise beam control matters, you might want to specify a lens with a longer focal length.
Mistake #3: Assuming 'Type A LED Tube' Means 'Plug and Play' for Any Fixture
One of my biggest regrets: not understanding the difference between Type A and Type B LED tubes before ordering for an office retrofit.
What is a Type A LED tube? It's designed to work with existing fluorescent ballasts. You remove the old fluorescent tube, install the LED tube, and it runs off the existing ballast. Simple, right?
Not always.
The mistake: I ordered 200 Type A LED tubes for a single-story office. What I didn't check was whether the existing ballasts were compatible with LED. Some older ballasts don't have enough starting voltage for LED tubes. The result? 200 tubes that flickered or didn't light at all.
Missing the ballast compatibility requirement resulted in a 3-day production delay and added cost for ballast bypass kits.
Step 1: Confirm Your Ballast Model
Before ordering Type A tubes, get the model number of the existing ballast. Check the manufacturer's compatibility list. Most LED tube makers publish a PDF. If your ballast isn't on the list, either upgrade the ballast or switch to Type B (direct wire) tubes.
Here's the thing: many installers will tell you 'any ballast works.' It doesn't. Based on my experience with about 50 retrofits, about 15% of older ballasts are incompatible with modern LED tubes.
Step 2: Understand Tube Labeling
Not all LED tubes are labeled clearly. Some say 'LED T8' but don't specify whether it's Type A or Type B. Always look for the fine print: 'Ballast Compatible' = Type A. 'Direct Wire' = Type B. 'UL Type A' or 'UL Type B' = clear designation.
On a 200-piece order where every single item had the ballast issue, I learned to check the spec sheet. Not the box. The spec sheet.
Step 3: Have a Backup Plan for Non-Compatible Fixtures
If you're ordering for a building with mixed ballast types (some old, some new), consider ordering Type B tubes and bypassing the ballast entirely. Or order a mix of Type A and Type B for different fixtures.
Dodged a bullet when I started ordering a small test batch (10 tubes) before committing to large quantities. Was one click away from ordering 500 tubes that would have been incompatible.
The Pre-Check Checklist (Printable)
Here's the checklist my team uses. It's pinned on our print rack:
- Recessed lighting: Check trim type, ceiling cavity depth, and trim lens focal point.
- Linear systems: Verify lens-to-LED distance. If lens sits inside focal point, expect diverging effect.
- Type A LED tubes: Confirm ballast model is on the compatibility list. Test with 10 units first.
- General: Always order 1-2 samples before full production. Always verify with a mockup if possible.
This list has saved us more than $1,200 over the past 18 months. I'm not saying you'll never make a mistake. But if you use this, you'll catch the expensive ones.