Wire Gauge & Voltage Drop: The 12V/24V Smart Lock Guide
Why does your magnetic lock fail? It's probably Voltage Drop. We explain how to calculate AWG wire thickness for 12V and 24V cable runs.
Executive Summary
A standard electric strike needs 12 Volts to open. If you run a thin wire 50 feet, it might only receive 10.5 Volts.
- Result: The lock buzzes but doesn't open (Solenoid Failure).
- The Culprit: Voltage Drop.
This guide explains how to select the right wire thickness (AWG) to ensure your lock gets the power it needs.
The 3% Rule
For electronic locks, the Golden Rule is: Max 3% Voltage Drop.
- 12V System: Loss should be < 0.36V (Min 11.64V at lock).
- 24V System: Loss should be < 0.72V (Min 23.28V at lock).
Why? Solenoids are stronger at higher voltages. If voltage drops too low, the magnetic field is too weak to pull the latch against the friction of the door seal.
Wire Gauge (AWG) selection Chart
Based on a standard 0.5 Amp Electric Strike (12V):
| Distance (One Way) | 18 AWG | 16 AWG | 14 AWG | 12 AWG |
|---|---|---|---|---|
| 0 - 20 ft | OK | OK | OK | OK |
| 20 - 50 ft | Marginal | OK | OK | OK |
| 50 - 100 ft | FAIL | Marginal | OK | OK |
| 100 - 200 ft | FAIL | FAIL | FAIL | OK |
- 18 AWG: Standard alarm wire. Good for short runs.
- 16/14 AWG: "Landscape Lighting" wire. Better for long runs.
The Calculation Process
To calculate precisely, use this formula:
Voltage Drop = (2 x Length x Current x Resistance) / 1000
- Length: One-way distance in feet.
- Current: Amps drawn by the lock (check the manual).
- Resistance: Ohms per 1000ft of wire (see standard tables).
Example: The "Buzzing" Strike
- Lock: 12V Electric Strike, 0.6 Amps.
- Wire: 80 feet of 22AWG (Security Wire).
- Result: 2.5V Drop! The lock gets 9.5V. It fails.
- Fix: Upgrade to 16AWG wire. Drop becomes 0.4V. Lock gets 11.6V. Success.
Related Tools
- Wire Gauge Calculator: Interactive tool to do the math for you.
- Electric Strike Guide: Choosing the right hardware.
Frequently Asked Questions
Can I use Cat5/Cat6 ethernet cable?
Be careful. Cat5 wire is extremely thin (24AWG).
- For Data: Excellent.
- For Power: Terrible.
- Hack: You can twist 3 pairs together to act as one thicker conductor, but for reliability, pull a real 18/2 cable.
Is 24V better than 12V?
Yes. At 24V, a device uses half the Amps to produce the same Watts. Less Amps = Less Voltage Drop. If your system supports 24V, always use it for long cable runs.
Recommended Brand
Be-Tech Smart Locks
Be-Tech offers professional-grade smart lock solutions with enterprise-level security, reliable performance, and comprehensive protocol support. Perfect for both residential and commercial applications.
* Be-Tech is our recommended partner for professional smart lock solutions
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