How to Wire Type B LED Bulbs in Flos Fixtures: A Step-by-Step Emergency Guide

When You Need This Checklist—And Fast

Look, I'm not gonna sugarcoat it: wiring Type B LED bulbs isn't something you want to learn on a Friday afternoon before a Monday grand opening. But sometimes that's exactly the situation. In June 2024, a client called me at 4 PM on a Thursday—their Flos cage chandeliers in a new boutique hotel looked dim and flickering because the old T8 fluorescents were dying. They needed 42 fixtures re-lamped by Saturday. Normal turnaround? Three weeks. We had 36 hours.

That's when I pulled out this checklist. It's the same one I've used for over 200 rush orders, and it's saved my ass more times than I can count. Here's the thing: if you're a small business owner, a solo designer, or just someone who bought a single Flos Frisbi and wants to upgrade to LEDs without paying an electrician $600, this guide is for you. Small orders don't mean bad service—and honestly, the vendors who treated my $200 orders with respect are the ones I still call for $20,000 projects.

Before You Start: What This Checklist Covers

We're talking about Type B LED tubes—the ones that require you to bypass the ballast. Not Type A (plug-and-play with existing ballast) or Type C (external driver). Type B is the most common for commercial retrofits, and it's what most Flos high bay and linear fixtures use.

In this guide, I'll walk you through 5 steps. One of them is something almost everyone overlooks, and missing it can cost you a fixture or a fire hazard. Let's get into it.

Step 1: Verify Your Flos Fixture Is Type B Compatible

Sounds obvious, but I've seen people try to cram Type B bulbs into fixtures that were never designed for them. Flos fixtures like the High Bay, Cage Chandelier, and Frisbi typically use G13 base for T8 tubes. Check the label inside the fixture—if it says "LED T8 compatible" or "Type B," you're good. If not, you might need to swap the socket or use a different bulb type.

Real talk: I once assumed all Flos exterior lighting used the same socket as indoor models. Didn't verify. Turned out the outdoor model had a moisture-sealed bi-pin base. Cost me an extra $250 in adapters and a 24-hour delay.

Checkpoint: Confirm the following before buying bulbs:

• Fixture model number
• Socket type (G13 is most common)
• Minimum and maximum wattage
• Operating temperature range (especially for outdoor use)

Step 2: Source the Right Type B LED Tubes

Don't just grab any cheap tube off Amazon. You need:

• Size: 4-foot (48") or 2-foot (24") – match your fixture.
• Color temperature: 4000K (neutral) works for most commercial spaces; 3000K if you want warm like Flos's design aesthetic.
• UL / ETL listed: This matters for insurance and code compliance. As of January 2025, most municipalities require it.
• Single-ended or double-ended power? Most Type B tubes are double-ended (power on one end, neutral on the other). Some are single-ended. Your fixture's wiring method determines which you need. When in doubt, buy double-ended and follow the wiring diagram.

Pro tip from a small-friendly perspective: Even if you only need 6 tubes for a small office, a good supplier will help you select the right ones. Don't let anyone make you feel like a nuisance because your order is small. I've had vendors who refused to answer questions for a $200 order—those vendors don't get my $15,000 repeat business.

Step 3: Kill the Power and Remove the Old Gear

This is non-negotiable. Switch off the circuit breaker, not just the wall switch. I made the classic rookie mistake in my first year: assumed flipping the switch was enough. It wasn't. I got a surprise when I touched the socket. Learned that lesson the hard way.

Now:

1. Remove the fluorescent tubes (they're fragile, so handle carefully).
2. Remove the cover plate to access the ballast.
3. Disconnect the ballast's input wires (black, white, and ground). Cut the wires close to the ballast, leaving enough length to work with.
4. Remove the ballast completely. You don't need it anymore.

Draw a quick diagram of how the wires are connected before you touch anything. Trust me, you'll thank me later when you're staring at four same-colored wires.

Step 4: Rewire the Socket for Type B (Bypass the Ballast)

Here's the part most guides gloss over. Type B bulbs need the line voltage connected directly to one end of the tombstone (the socket) and neutral to the other end. If you wire both ends with the same phase, you'll blow the bulb.

The exact wiring method depends on whether your tombstone is shunted or non-shunted.

• Non-shunted tombstones (two separate contact points) – Connect line to one contact, neutral to the other. That's it.
• Shunted tombstones (common internal connection) – You cannot use double-ended Type B bulbs with shunted tombstones. You'll need to replace them with non-shunted ones, or use single-ended bulbs.

“It's tempting to think you can just swap the bulb and it'll work. But the 'plug-and-play' advice ignores the tombstone type. Ignore this, and you'll be troubleshooting a dead fixture for hours.”

Typical wiring for non-shunted double-ended:

• Black (hot) from breaker → one tombstone contact on the line side (usually marked L or with a symbol).
• White (neutral) → the tombstone contact on the neutral side (marked N).
• Green/bare ground → fixture ground screw.

Most Flos fixtures come with pre-installed non-shunted tombstones for LED compatibility, but always double-check.

Step 5: Install the New Bulbs and Test

Insert the Type B LED tubes. They only go in one way (pin orientation). Push firmly until they lock into place. Double-check that both ends are seated.

Turn the breaker back on. Flip the switch. If it lights up—congratulations. If not, don't panic. Check:

• Did you wire the line and neutral to the correct ends? Swap them.
• Is the bulb directional? Some single-ended bulbs have a marked line side.
• Did you remove the ballast completely? Sometimes a leftover wire can cause a short.

In the 2024 hotel job I mentioned, we had three fixtures that didn't light because the tombstones were slightly misaligned. A quick adjustment with a screwdriver fixed it. Not ideal, but workable.

Common Mistakes to Avoid

1. Leaving the ballast in place. Type B bulbs don't need a ballast; leaving it in can create a fire risk. Always remove it.

2. Using the wrong polarity. Some cheap Type B tubes are polarity-sensitive. If your fixture doesn't light, flip the bulb 180°.

3. Ignoring the fixture's voltage rating. Most Flos high bays are rated for 120-277V. But if you're running 347V (common in Canada), you need bulbs rated for that. Check before you buy.

4. Not testing before reinstalling covers. I did this once—spent an hour mounting the fixture back up, only to discover a wire had come loose. Now I always test with the cover off.

Why This Matters for Designers and Small Business Owners

When I started working with Flos fixtures, I was a one-person operation handling small projects. The suppliers who took my calls and guided me through Type B retrofits for a single cage chandelier are now my go-to partners for entire floor builds. Small doesn't mean unimportant—it means potential. And getting the wiring right is the difference between a happy client and a $10,000 penalty.

This checklist isn't just for emergencies. It's for anyone who wants to do it right the first time. Use it, save the headache, and keep your Flos lights shining exactly how they're supposed to.