Emergency Light Voltages and Voltage Drop Calculations
- Emergency Light Voltage
- Understanding Voltage Drop
- Calculating Voltage Drop
- Formulas: Amps, Volts, Watts
- Voltage Drop Examples
- Browse Emergency Lights
Emergency Light Voltage
The most common voltage for emergency lights is 6 VDC. This means the power from the building’s electrical system—typically 120 volts—must be stepped down and converted to DC current. The reason? Batteries don’t run on AC power. When installing remote heads, the distance from the main unit plays a critical role in determining performance, especially due to voltage drop.
Understanding Voltage Drop
All wire has some resistance, which restricts the flow of electrons and causes voltage drop. For short distances, this is negligible. But over hundreds of feet, voltage drop can reduce power to your lamp, affecting brightness. Most designers aim for a maximum of 5% voltage drop. Thicker wires (lower gauge) reduce voltage drop and help maintain optimal illumination levels.
Calculating Voltage Drop
Use the table below to estimate voltage drop for different wire gauges and load currents:
| Wire Gauge | 0.5 A | 1 A | 2 A | 4 A | 10 A |
|---|---|---|---|---|---|
| 10 | 0.10% | 0.20% | 0.40% | 0.80% | 2.00% |
| 12 | 0.16% | 0.32% | 0.64% | 1.27% | 3.18% |
| 14 | 0.25% | 0.50% | 1.01% | 2.02% | 5.04% |
| 16 | 0.40% | 0.80% | 1.60% | 3.20% | 8.00% |
| 18 | 0.64% | 1.27% | 2.54% | 5.08% | 12.71% |
| 20 | 1.01% | 2.02% | 4.03% | 8.07% | 20.17% |
| 22 | 1.60% | 3.20% | 6.40% | 12.81% | 32.02% |
Formulas: Amps, Volts, Watts
These simple formulas help you calculate electrical load and sizing:
- Watts = Amps × Volts
- Volts = Watts ÷ Amps
- Amps = Watts ÷ Volts
Example: A 6V emergency lamp with a 9W bulb uses 1.5 amps (9 ÷ 6 = 1.5 A).
Voltage Drop Examples
Scenario 1: A 12W remote head placed 300 feet from a 6V battery draws 2 amps (12 ÷ 6). Using 18-gauge wire gives a 7.62% drop, exceeding the 5% standard. Switching to 16-gauge reduces the drop to 4.8%, which is acceptable.
Scenario 2: The same installation with a 24V system draws only 0.5 amps (12 ÷ 24). Using 18-gauge wire results in just a 1.96% drop. Even using 22-gauge wire, the drop is still below 5% at 4.8%.
Scenario 3: With a 24V system and a 25W remote head over 300 feet of 18-gauge wire, the drop is 3.125%. You could even go 475 feet before hitting 5% drop.
Browse Emergency Lights
Need lights that can handle voltage drop across long distances? Check out our full selection of compliant options at Emergency lights.