My 8-Step LED Lighting Order Checklist: Downlights, Spotlights, Dimming, and Contactor Wiring

I'm the office administrator for a 210-person company. I handle facilities purchasing — roughly $180,000 a year across about a dozen vendors, three of them electrical distributors. I'm not an electrician and I'm not a lighting designer. I'm the person who gets the email when a conference room looks like a hospital corridor.

This checklist is for whoever has that job. Eight steps, roughly a week of calendar time, and it works whether you're ordering six downlights for a reception area or sixty for an entire floor.

One boundary up front, and I mean it: if you're specifying roadway, sports, or high-bay industrial lighting, this isn't your checklist. Those need photometric layouts and someone who does them for a living. I watched an office manager try to spec parking lot lighting off a catalog photo once. It went badly. Knowing which jobs to hand off is most of the job.

Step 1: Write down the application before you write the spec

Before anyone touches a catalog, answer four questions on paper:

• What's the fixture type — downlight, spotlight, panel, strip?
• What's the ceiling height and the existing cutout size?
• Is the space damp, wet, or insulated? A bathroom needs a wet-location rating; a recessed fixture touching insulation needs an IC rating.
• Who's using the room, and for what?

That last one matters more than people think. A 4,000K fixture that reads as "crisp and modern" in a warehouse reads as "dentist's office" in a client lounge. Same fixture. Different room.

Step 2: Measure the existing fixture — don't trust the model number

Pull one down and measure the cutout. I've found 4-inch, 5-inch, and 6-inch cans on the same floor because three different contractors built it out over fifteen years. Get the plenum depth while you're up there, and photograph the junction box. If you can't get above the ceiling, that's a real constraint — some commercial downlight fixtures need more clearance than the grid gives you.

The classic error here, and I made it in my first year managing this account: I ordered forty downlights based on the product photo and the phrase "fits standard 6-inch cans." Cost me a restocking fee and two weeks of a dark hallway. "Standard" means something different to every manufacturer. Measure. Every time.

Step 3: Read the photometric data, not the marketing copy

The box says "warm white." That tells you nothing. What you want on the spec sheet:

• CCT in Kelvin — 2700K, 3000K, 3500K, 4000K
• Lumens, and at what CCT, because a fixture rated at 1,100 lm at 4000K puts out less at 2700K
• CRI (or better, TM-30 values), especially R9 if anyone in that room looks at fabric, food, or faces
• Beam angle if it's an LED spotlight — 15° and 36° are not interchangeable in a lobby with artwork

Here's something most people don't realize: "warm white" spans roughly 2700K to 3500K depending on who's printing the box, and mixing two brands in the same hallway usually shows. I said "warm white" on a purchase order once. My vendor shipped 3500K. Our design consultant meant 2700K. We were using the same words and meaning different things, and we found out the day the fixtures went in. Now I write the Kelvin number on the PO and nothing else.

Step 4: Match the controls before you match the fixture

This is where most flicker complaints are born. A "dimmable" LED is only dimmable with the right dimmer, and the compatibility list is specific per driver, not per brand.

Two things to check:

1. Dimmer type. Phase-cut (triac or ELV) versus 0-10V versus a proprietary wireless protocol. If the existing wall box has a residential leading-edge dimmer and the new fixture wants 0-10V, it won't work — not "won't work well," just won't.
2. Minimum load. Many dimmers need a minimum wattage draw. Ten watts of LED on a 600W dimmer can flicker, buzz, or refuse to shut off completely.

On 0-10V wiring, the convention I see on most commercial fixtures is a purple (violet) lead for the control signal and gray for common, though older 1-10V gear sometimes uses pink. Check the fixture's own wiring diagram. Don't trust a photo from a forum — I've seen three different color conventions in a single submittal package.

Why does an LED light bulb flicker? Run this five-item check

Diagnose in this order, cheapest test first:

1. Swap the lamp or fixture with a known-good one in the same socket. If the problem moves with it, it's the fixture. If it stays, it's the circuit.
2. Check the dimmer's compatibility list against the actual fixture model number. Not the brand — the model.
3. Check for a loose neutral or a backstabbed connection at the switch. Flicker that shows up under load often means a bad termination.
4. Test without the dimmer. If it's steady on a plain switch, you've found your answer.
5. Look at it through your phone camera. Rolling shutter makes some flicker visible on video that your eye glosses over. If the camera sees it, it's real — IEEE 1789-2015, the recommended practice for modulating LED current, is the reference most lighting engineers use for what counts as an acceptable level, and its limits get stricter as frequency drops. Worth asking about if the space gets used for video calls.

One cause people miss entirely: a fixture that glows faintly or blinks when the switch is off. That's usually induced ("phantom") voltage on a long switch leg — LEDs draw so little current that a few volts of coupling is enough to light them. A compatible dimmer or a small load resistor fixes it. It's not a defective fixture, and returning it won't help.

Step 5: Get the electrician involved before you order anything on a contactor

If the fixtures are switched by a lighting contactor, timeclock, or photocell — parking lots, exterior signage, some warehouse bays — stop and loop in your licensed electrician. Not because it's exotic, but because the failure mode is expensive. A contactor with the wrong coil voltage or a reversed line/load either won't switch or switches something you didn't intend.

What I've learned to ask for, and you should too:

• The manufacturer's wiring diagram, from the manufacturer's own documentation — not a third-party photo. Lighting contactors ship with an instruction sheet; the documentation from brands like GE Lighting includes the diagram for each configuration. Use the one that came with your unit.
• Coil voltage. A 120V coil and a 24V coil contactor look identical on a shelf.
• Line versus load. It's marked on the contactor. Verify it before anyone lands a wire.
• Class 2 separation. If low-voltage control wiring runs alongside 277V power conductors, NEC Article 725 separation rules apply. Don't let anyone zip-tie them together "to keep it neat."

I learned the coil-voltage lesson the hard way in 2021, when a box of contactors arrived for an exterior lighting retrofit and two of the four were the wrong coil. We ate a restocking fee and pushed the install three days. Nobody warns you that the part number matters on those.

Boundary time again: I don't terminate conductors and I don't open panels. I buy the parts, I schedule the electrician, and I keep the drawings. If your facility manager or landlord requires a licensed contractor, that's not overhead — that's the insurance policy.

Step 6: If it's smart, verify the ecosystem — and don't believe blanket compatibility claims

Smart fixtures, sensors, and cameras all introduce the same question: what controls what, and over which protocol. Zigbee devices, Wi-Fi devices, and proprietary app-based systems don't automatically talk to each other just because they're all labeled "smart."

If a purchase includes a smart outdoor camera alongside exterior lighting, get three answers in writing:

1. Which app, and which hub (if any)?
2. Which protocol — Zigbee, Wi-Fi, Bluetooth, or a proprietary bridge?
3. What happens when the internet goes down?

What I'd point out here is that buying into a single ecosystem solves most of this. If the camera, the bulbs, and the outdoor fixtures are all designed for one app over one protocol — the way the Cync line is built, for instance — the compatibility question mostly evaporates. Assembling a system from four brands is cheaper on paper and costs you weekends.

And nobody can honestly guarantee their gear will play nicely with every third-party system. I've asked. A vendor who says "it works with everything" is telling you something about their honesty, not their product. The vendor who says "it works with these four, and here's what to do if you're on something else" is the one I keep calling.

Step 7: Order one. Install one. Live with it for a week.

This is the step people skip, and it's the one that saves the most money. Order a single unit of the exact model, install it in the actual space, and use it for a week — at night, with the dimmer at 20%, and on a video call.

Check for audible buzz at low dim, color shift as it dims down, visible flicker on camera, and whether the beam actually lands where you expected at the mounting height you actually have. If one fixture fails a test, you're out $60. If sixty fail, you're out a month.

In my experience, the pilot test is the single highest-return step on this list. To be fair, it does slow down a project that's already behind schedule — I've been tempted to skip it plenty of times. Every time I skipped it, I regretted it.

Step 8: Lock the model number into the paperwork

Once the pilot passes, write the exact model number and CCT into a one-line spec you reuse on every order. Then:

• Order 5–10% extra as attic stock. Fixtures get discontinued fast, and a 2027 replacement that doesn't match the 2024 fixtures is a visible problem in a corridor.
• Keep the spec sheet and the invoice with the model number on it. Warranty claims without a model number move slowly.
• Note the date you standardized it. When it's time to buy again, you'll want to know how old that spec is.

Four mistakes I still see (and one I keep making)

Mixing CCTs across a floor. Two vendors, two orders, 3000K and 3500K, and now the hallway has a visible seam. Write the Kelvin value on the PO.

Buying on price for the pilot and on spec for the rest. It works right up until the budget model is the one at the reception desk where clients stand.

Trusting "dimmable" without a dimmer list. It's on the box. It means almost nothing.

Reading the wiring diagram off the internet. I still catch myself doing this. The diagram on the inside of the cover, or in the manufacturer's instruction sheet, matches your actual unit. Forum photos don't.

And the one I keep making: assuming everyone means the same thing by "standard size." They don't. I'm not sure they ever will.

References I actually check before a purchase: NEC (NFPA 70) Article 725 for Class 2 control wiring separation and Article 410 for luminaire installation; IEEE 1789-2015 for LED flicker recommendations; and the manufacturer's own wiring diagrams and dimmer compatibility lists. Pricing and lead times mentioned here reflect early 2025 quotes from three distributors — lighting lead times move fast, so get current quotes before you budget.