The Commercial Access Control Cabling Guide Nobody Actually Writes About
When businesses start planning a security upgrade, most of the conversation centers on the hardware - which reader brand, which software platform, whether to go biometric or mobile credential.
The cabling doesn't come up until something goes wrong.
That's backwards. Access control systems run on low voltage power, typically 12V or 24V DC, and every device in the system depends on specific cabling configurations to transmit data and hold a door locked. Get the infrastructure wrong and it doesn't matter how sophisticated the hardware is, you'll be chasing intermittent failures, failed inspections, and doors that don't behave the way they're supposed to.
Whether you're migrating from a legacy system or starting from scratch, here's what you actually need to know about low voltage cabling for commercial access control.
What's actually happening at a single door
Most people think of an access control door as one device. It's not. Securing a single commercial door means coordinating four separate devices back to a central panel, and each one has its own cabling requirement.
The Card Reader: The card reader handles both power and data transmission. It typically runs on a shielded 22/6 AWG cable. Grounding the shield matters. Skip it and electromagnetic interference will skew the data signal in ways that are annoying to diagnose.
The Lock: The lock-whether that's an electric strike or a maglock needs heavy-duty power to physically release the door. That means an 18/4 AWG cable, which features 18 gauge and 4 conductors.
The Request-to-Exit (PIR REX): The request-to-exit sensor is the motion sensor or push button that lets people leave freely without badging out. A 22/4 AWG cable is used for the PIR REX.
The Door Position Switch (DPS): The door position switch (DPS) is the sensor that tells the panel whether the door is propped open or fully closed. This runs on a 22/2 AWG cable.
Why contractors use composite "banana cable"
Pulling four separate cables to every door in a commercial facility is exactly as labor-intensive as it sounds. The banana cable is called that because of how it peels especially the cable that does not have the outer jacket and has all 4 cables connected to a core to peel.
Banana cable bundles all four runs into a single master jacket. One pull per door instead of four. The inner cables are color-coded typically orange for the reader, gray for lock power, blue for REX, white for the door contact - which makes terminations at the panel significantly cleaner and cuts down on wiring errors that only surface after the system is live.
It also keeps ceiling trays and conduit from turning into a mess that nobody wants to troubleshoot eighteen months later.
OSDP vs. Wiegand - and why the protocol choice affects your cabling
If you're specifying a new system, the communication protocol you select has direct implications for how the cabling gets designed.
Wiegand was the industry standard for decades. It still works, but it has real limitations: it's unencrypted, it only transmits in one direction, and readers have to be within roughly 500 feet of the access control panel. In a large warehouse or a multi-story building, that last constraint creates layout problems that are expensive to work around.
OSDP - Open Supervised Device Protocol - is the current standard for good reason. It uses AES-128 encryption, which means badge data is actually protected in transit rather than just hoping no one is listening. It runs on an RS-485 serial connection that extends reader placement up to nearly 4,000 feet from the controller. When comparing the wiring itself, a legacy Wiegand cable is just 6 conductors, whereas the OSDP RS-485 cable has twisted pairs (typically 3 pairs of twisted cable).
If you're upgrading from Wiegand to OSDP, the cabling conversation needs to happen early. Your low voltage contractor needs to pull cable rated for RS-485 transmission - it's not the same thing as what's already in the wall.
Plenum vs. riser - the code compliance piece that gets skipped
This is the part that creates problems during the fire marshal inspection.
Commercial buildings have strict fire safety regulations around cable jacketing, and the type of cable you can legally run depends entirely on where it's going.
Plenum-rated cable (CMP) is required any time you're running cable through a drop ceiling or raised floor that's part of the building's HVAC air circulation system. These spaces are called plenum spaces, and the cables that run through them have to use fire-retardant jacketing that produces low smoke and minimal toxic fumes if burned. Run the wrong cable through a plenum space and you have a code violation - regardless of whether anyone notices during installation.
Riser-rated cable (CMR) is what gets used for vertical runs between floors in elevator shafts and non-plenum conduit.
A qualified low voltage contractor knows which rating your building requires before a single cable gets pulled. If that conversation isn't happening upfront, it's worth asking why.
The bottom line
Access control infrastructure is one of those things that's invisible when it's done right and very visible when it isn't. The hardware on the wall is what everyone sees but what's in the ceiling determines whether the system actually performs.
If you're planning an access control upgrade or new installation and want to understand what the right infrastructure looks like for your facility, that's exactly the kind of conversation scDataCom is built for. We're a licensed commercial security contractor based in Savannah, GA, working in commercial facilities across Georgia and Florida.
Let's look at what you're working with before anything gets pulled.