Choosing the right wire gauge for your access control system is crucial for ensuring reliable performance and avoiding voltage drops that could impair the system’s functionality. This guide provides updated insights on determining the correct wire gauge size based on current load, voltage, and distance.
Determining the Correct Wire Gauge
To select the appropriate wire gauge for a circuit in an access control system, you need the following information:
- Quantity, Voltage, and Current Draw of Devices: Identify the total number of locks and other powered devices on the circuit, along with their voltage and current draw (in amps).
- Distance: Measure the distance in feet from the power supply to the farthest lock on the circuit.
Step-by-Step Process
- Calculate Total Current Draw:
- Add together the current draw (amps) of all locks and powered devices on the same circuit.
- Determine Distance:
- Measure the distance from the power supply to the furthest lock.
- Cross-reference:
- Use the total current draw and the distance to determine the appropriate wire gauge from the chart provided below.
One Circuit Configuration
When referring to “one circuit,” it implies running two wires from the power supply to one or more locks in parallel. Ensure that the last lock on the pair of wires does not exceed the maximum distance shown in the chart for the specified wire gauge and total current draw.
Creating Multiple Circuits
If the wire gauge size or maximum distance is inadequate for your application, consider splitting the quantity of locks into two or more separate circuits. Use the chart to determine the appropriate wire gauge for each new circuit independently. It is recommended to provide two fuse-protected circuits for each opening:
- One circuit for locking devices (inductive loads)
- One circuit for access controllers and signaling devices (resistive loads)
This approach allows for the use of significantly smaller gauge wire, increased distance, and protects access control and signaling devices from potential damage caused by inductive load devices.
Compliance
Ensure that all wiring is installed in accordance with state and local codes.
Wire Gauge and Distance Chart
Below are the charts for determining the minimum wire gauge for 12 volts AC or DC, based on the current draw and distance, allowing a 5% voltage drop from the power supply to the furthest load on one circuit.
Chart: Minimum Wire Gauge for 12 Volts AC or DC
Maximum Distance Allowable for a 5% Voltage Drop
| Amps | 25ft | 50ft | 75ft | 100ft | 150ft | 200ft | 250ft | 300ft | 350ft | 400ft | 500ft |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.125 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 18 | 18 | 18 | 16 |
| 0.25 | 20 | 20 | 20 | 20 | 18 | 18 | 16 | 16 | 16 | 14 | 14 |
| 0.35 | 20 | 20 | 20 | 18 | 18 | 16 | 16 | 14 | 14 | 14 | – |
| 0.50 | 20 | 20 | 18 | 18 | 16 | 14 | 14 | 14 | 14 | – | – |
| 0.75 | 20 | 18 | 18 | 16 | 14 | 14 | 14 | – | – | – | – |
| 1.00 | 20 | 18 | 16 | 14 | 14 | 14 | – | – | – | – | – |
| 1.50 | 18 | 18 | 16 | 14 | 14 | – | – | – | – | – | – |
| 2.00 | 18 | 16 | 14 | 14 | – | – | – | – | – | – | – |
| 2.50 | 18 | 14 | 14 | 14 | – | – | – | – | – | – | – |
| 3.00 | 16 | 14 | 14 | – | – | – | – | – | – | – | – |
| 3.50 | 16 | 14 | – | – | – | – | – | – | – | – | – |
| 4 to 6 | 14 | – | – | – | – | – | – | – | – | – | – |
Chart: Minimum Wire Gauge for 12 Volts AC or DC (Extended)
| Amps | 25ft | 50ft | 75ft | 100ft | 150ft | 200ft | 250ft | 300ft | 350ft | 400ft | 500ft |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.125 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 |
| 0.25 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 18 | 18 | 18 | 16 |
| 0.35 | 20 | 20 | 20 | 20 | 20 | 18 | 18 | 18 | 16 | 16 | 14 |
| 0.50 | 20 | 20 | 20 | 20 | 18 | 18 | 16 | 16 | 16 | 14 | 14 |
| 0.75 | 20 | 20 | 20 | 18 | 16 | 16 | 16 | 14 | 14 | 14 | – |
| 1.00 | 20 | 20 | 18 | 18 | 16 | 16 | 14 | 14 | – | – | – |
| 1.50 | 20 | 18 | 18 | 16 | 16 | 14 | 14 | – | – | – | – |
| 2.00 | 18 | 18 | 16 | 16 | 14 | 14 | – | – | – | – | – |
| 2.50 | 18 | 18 | 16 | 14 | 14 | – | – | – | – | – | – |
| 3.00 | 18 | 16 | 14 | 14 | 14 | – | – | – | – | – | – |
| 3.50 | 18 | 16 | 14 | 14 | – | – | – | – | – | – | – |
| 4 | 16 | 16 | 14 | – | – | – | – | – | – | – | – |
| 5 | 16 | 14 | 14 | – | – | – | – | – | – | – | – |
By selecting the appropriate wire gauge for your access control system, you can ensure reliable operation, minimize voltage drop, and extend the longevity of your system components. Use the provided charts and guidelines to make informed decisions and effectively manage your access control wiring requirements. Always consult with a professional installer or electrician for complex systems and ensure compliance with local codes.