ABB Contactors & PLC Lighting: 7 Questions Facility Buyers Actually Ask

So you're looking into using ABB contactors for a PLC-based lighting setup. Or maybe you're not sure if you even need a contactor. The line between lighting control, motor control, and general switching can get blurry fast. Especially when you're sitting in front of a parts catalogue with about 50 different ABB contactor models.

I handle purchasing for a mid-sized manufacturing facility—nothing huge, but enough that I'm ordering electrical components several times a month. This is what I've learned (sometimes the hard way) about mixing ABB contactors with PLC lighting systems.

1. Can I use a standard ABB contactor (like A40-30-10) for PLC-controlled lighting?

Short answer: yes, but you need to check the coil voltage. This is the mistake I made in my first year—I ordered a bunch of A40-30-10 contactors with 230V AC coils, and then realized our PLC outputs were 24V DC. The contactor coil needs to match what the PLC can drive.

ABB's A-line contactors (A9-30-10, A26-30-10, A40-30-10, A75-30, etc.) come with different coil voltages: 24V DC, 24V AC, 110V AC, 230V AC, 400V AC. Check the coil suffix on the model number. If your PLC has 24V DC outputs, you want a contactor with a 24V DC coil—or you add an interposing relay. We ended up using A9-30-10-84 (24V DC coil) for most of our lighting zones.

This was accurate as of mid-2024. ABB does update their coil offerings, so verify current catalog numbers before ordering.

2. What's the difference between a "definite purpose contactor" and a standard ABB contactor for lighting?

This tripped me up when I first started. Definite purpose contactors (DP contactors) are designed specifically for HVAC and lighting applications. They're typically more compact and cheaper than a general-purpose contactor like the A-line. ABB makes them—look for the DP series.

The trade-off: DP contactors often have lower short-circuit current ratings and aren't designed for the same mechanical duty cycle as an A-line contactor. For a lighting panel that switches on/off a few times a day? A DP contactor is fine. For a production line lighting system that cycles 20+ times per day (say, with occupancy sensors)? Stick with the A-line. I leaned —or rather, a senior electrician convinced me —to use A-line for anything that cycles frequently.

3. Can ABB AF contactors (like AF09 or AF30) handle LED lighting loads?

This is one of those "readers should know this but might not" questions. AF series contactors are the electronic coil versions. They're great for PLC control because they can handle a wide control voltage range (24-60V DC, for example) without needing to swap coils. But here's the catch with LEDs.

LED drivers have high inrush current —think 20x to 50x the steady-state current for a few milliseconds. Standard contactors are rated for this, but you need to check the actual inrush rating, not just the continuous current. In one project, we spec'd AF09 contactors for a 5-amp LED load and had contact welding issues after three months. Turned out the LED inrush exceeded the contactor's rating. We upsized to AF16 and the problem went away.

4. How do I wire an ABB contactor to a PLC output for lighting control?

The basic setup is straightforward:

• PLC digital output → contactor coil (A1-A2 terminals on ABB contactors)
• Contactor power contacts → lighting circuit (L1, L2, L3 for 3-phase; or single-pole for single-phase)
• Auxiliary contacts (if used) → status feedback to PLC input

One thing I learned: put a flyback diode across the DC coil (A1-A2). When the PLC turns off the output, the coil collapses and generates a voltage spike. Without the diode, that spike can damage the PLC output or cause random resets. I fried one PLC output card before figuring this out. Cost me about $300 in downtime and a new output module.

5. For PLC lighting, should I use a reversing contactor or just a standard one?

Probably not, unless you're doing something unusual. Reversing contactors (like ABB's R-series or two A-line contactors mechanically interlocked) are for motors that need to spin in both directions. For lighting, you're just on/off. A standard contactor does the job.

Exception: if you're doing emergency lighting testing where you need to switch between mains and backup power, you might use a mechanically interlocked pair. But that's a specific scenario, not the norm.

6. What auxilary contact blocks do I need for status feedback to the PLC?

ABB contactors accept auxiliary contact blocks that snap onto the front or side. Common options:

• CA5-01: 1 N.C. contact
• CA5-10: 1 N.O. contact
• CA7-20E: 2 N.O., electronic (for low-voltage PLC inputs)

If you're feeding status back to a 24V DC PLC input, use the CA7-20E or another "electronic" auxiliary. Standard contacts can have bounce or low-voltage issues. Not a huge deal, but I've seen PLC inputs falsely register a closed contactor due to contact resistance. Using the electronic aux blocks eliminated that.

7. Do I need a separate lighting contactor panel, or can I put ABB contactors in the main panel?

Both work, but code and practicality matter. For small installations (say, 4-6 lighting zones), putting contactors in the main panel is fine. For anything larger, a dedicated lighting contactor panel is cleaner and safer.

I consolidated a system that had 12 contactors crammed into a main panel. It was a mess of wires and made troubleshooting a nightmare. We moved to a dedicated enclosure using ABB AF contactors with a common neutral bar and individual circuit breakers. The installation passed inspection faster, and maintenance hasn't complained once.

Based on what we've seen in our facility and from talking to other facility managers, I'd say plan for a dedicated lighting contactor panel once you exceed 8 zones. The upfront cost is higher, but the ease of maintenance pays for itself within a year or two.