The $3,200 Mistake That Changed How I Spec Power Supplies

Back in September 2022, I spec'd a retrofit of 48 LED tube lights for a small office. The client wanted to replace old fluorescent T8s with LED tubes. Simple enough, right? I ordered 48 Mean Well LPC-60-700 drivers—rated for 700mA constant current—without double-checking the tube requirements.

Three days later, the shipment arrived. The tubes were installed. Eight of them flickered within the first hour. By the end of the day, four were dead. The client called me, not happy. I pulled two dead tubes and drove back to the shop. That's when I realized: the tubes specified 24V DC input, not constant current. My LPC-60-700 was a constant current driver, not a constant voltage power supply.

The total cost: $3,200—48 tubes, 48 drivers, labor, and the expedited replacement of the correct Mean Well LRS-150-24 (a 24V 5A model) plus additional DIN rail power supplies for the distribution. The mistake wasted roughly $890 in materials and a full week of downtime.

What I Thought the Problem Was

At first, I blamed the tube manufacturer. "The tubes are faulty," I told myself. But after testing with a benchtop supply, they worked perfectly at 24V. Then I blamed the Mean Well driver. I checked the datasheet: output 54-86V, 700mA, 48W. The tubes were 24V, 1.5A each (36W). Voltage mismatch. The driver was trying to push its output voltage up to 54V+, and the tubes couldn't take it.

This is where most people stop: "I used the wrong type of driver." But that surface-level diagnosis hides a deeper issue.

The Real Problem: Confusing Constant Current vs Constant Voltage

Here's the thing: many LED tube lights run on constant voltage (24VDC or 48VDC), while many strip lights and downlights use constant current drivers. I knew this in theory. But in practice, the datasheet for the mean well led drivers looked similar—same form factor, same wire colors. The spec sheet for the tube said "24V DC input" in fine print. I skimmed it, saw "LED driver required," and grabbed the LPC-60-700 because it was sitting on my shelf.

The deeper cause: I didn't match the power supply type to the fixture's input requirement. It's not just about wattage. A constant current driver regulates current (mA), while a constant voltage supply regulates voltage (V). Plug a CV fixture into a CC driver and bad things happen. In my case, the driver's open-circuit voltage exceeded the tube's maximum rating, damaging the internal circuitry.

Another Layer: The 3-in-1 Dimming Trap

Around that same time, I almost made another mistake. The client also wanted dimmable tube lights in the conference room. I was about to order standard Mean Well HDR-60-24 (a DIN rail power supply) and pair it with a trailing-edge dimmer. But the tubes I selected only supported 0-10V dimming (which, honestly, I didn't check until the last minute).

I ended up using Mean Well LPC-60-700 (constant current) with 3-in-1 dimming (resistor/PWM/voltage) for the downlights, and a separate Mean Well ELG-100-24 (constant voltage, 0-10V dimmable) for the tubes. That worked. But it taught me: even within the Mean Well range, the dimming method varies by series. The mean well 3-in-1 dimming resistor range is great for constant current drivers, but if you need dimming on a constant voltage supply for tubes, you need a model with 0-10V or DALI option.

The Cost of Ignoring This

Let's quantify. On that $3,200 order, I personally made the error. But multiply that across a larger project. I've seen colleagues order 50+ units of LRS-350-24 for a warehouse LED strip installation, only to discover the strips required 48VDC. That's a $1,500 mistake—plus return shipping and delay penalties.

Another common scenario: using a mean well 24v 5a power supply (like LRS-150-24) for spotlight outdoor fixtures that actually need a constant current driver with IP67 rating. The 24V supply might power a single spotlight, but if you daisy-chain multiple, voltage drop and overload happen quickly. I've seen a $2,200 outdoor landscape lighting job fail because of that oversight.

The numbers said go with a generic constant current driver that was 15% cheaper. My gut said stick with Mean Well. I went with my gut and ordered Mean Well ELG-100-42 instead. Later learned the generic driver had reliability issues I hadn't discovered in my research. Gut check: trust the brand, but verify the model.

The Checklist I Now Use (And What You Can Steal)

After the third rejection in Q1 2024 (yes, I made similar mistakes twice more—on smaller orders), I created our team's pre-check list. We've caught 47 potential errors using this in the past 18 months. Here's the simplified version:

  • Fixture input type: Constant voltage (specify voltage) or constant current (specify current range)? This is the #1 mistake.
  • Wattage match: Total load ≤ 80% of power supply rated wattage.
  • Dimming compatibility: Trailing edge, 0-10V, DALI, PWM? Verify both fixture and driver support the same protocol.
  • Environmental rating: Indoor/outdoor? IP20 for indoors, IP67 for spotlight outdoor or damp locations.
  • Form factor: Enclosed (LRS), DIN rail (HDR), or waterproof (HLG)? Consider installation space.

To be fair, most of these checks are obvious—when you're not in a hurry. I get why people skip them: budgets are tight, timelines are short, and the wrong power supply looks the same as the right one. But the hidden cost of a field failure is huge.

I'm not 100% sure, but I estimate our team has saved roughly $15,000 in potential rework thanks to this checklist. Take this with a grain of salt: your mileage may vary. But if you're specifying mean well led drivers or mean well 24v 5a power supply models for led tube light vs normal tube light retrofits, at least verify the voltage type first.

One More Thing: The "Normal Tube Light" Assumption

Speaking of led tube light vs normal tube light: many people assume you can just swap a fluorescent tube for an LED tube using the same ballast. That's sometimes true, sometimes not. If you're using a Type A LED tube (compatible with existing ballast), you don't need an external driver. But if you're using Type B LED tube (direct wire, line voltage), you need a compatible driver—usually a constant voltage power supply like the Mean Well LRS-150-24. I've made the mistake of ordering Type B tubes and using constant current drivers (surprise, surprise).

Decision time: which type are you using? If you're not sure, ask the manufacturer. And please—don't just guess based on the tube shape. I learned that the hard way.