Grab-and-go tables to size copper wire for remote heads using a ~5% voltage drop target. Includes one-way distance limits for 6V / 12V / 24V systems across AWG 18–10, a quick formula, and worked examples. For products, see LED remote head emergency lights; for fundamentals, use the remote head sizing & wiring guide.
Last updated: June 2026
How to Use These Tables
- Pick your system voltage (6V / 12V / 24V).
- Total the branch load in watts (all heads powered on that run at once).
- Find the row for your watts and the column for your wire gauge.
- The value shown is the approx. one-way max distance (ft) to stay near a 5% drop target.
- If your run is longer: upsize wire or step up voltage (see 12V vs 24V for long runs).
Assumptions & Method
- Target: ~5% voltage drop at full emergency load.
- One-way distance shown (round-trip accounted for in calculations).
- Copper resistance @ 20 °C (ohms/1000 ft): AWG 18 = 6.385, 16 = 4.016, 14 = 2.525, 12 = 1.588, 10 = 0.999.
-
Formula:
I = P/V, round-tripRfrom AWG table, thenV_drop ≈ I × Rand requireV_drop ≤ 0.05 × V_system. - Reality checks: Battery voltage sags during the 90-minute test; temperature and terminations matter. Verify brightness at the farthest head near the end of the test.
Tables — 12V Systems (One-Way Max Distance @ ~5% Drop)
| Load (W) | AWG 18 | AWG 16 | AWG 14 | AWG 12 | AWG 10 |
|---|---|---|---|---|---|
| 5 | 113 ft | 179 ft | 285 ft | 453 ft | 721 ft |
| 10 | 56 ft | 90 ft | 143 ft | 227 ft | 360 ft |
| 20 | 28 ft | 45 ft | 71 ft | 113 ft | 180 ft |
Tables — 24V Systems (One-Way Max Distance @ ~5% Drop)
| Load (W) | AWG 18 | AWG 16 | AWG 14 | AWG 12 | AWG 10 |
|---|---|---|---|---|---|
| 5 | 451 ft | 717 ft | 1,141 ft | 1,814 ft | 2,883 ft |
| 10 | 226 ft | 359 ft | 570 ft | 907 ft | 1,441 ft |
| 20 | 113 ft | 179 ft | 285 ft | 453 ft | 721 ft |
Tables — 6V Systems (One-Way Max Distance @ ~5% Drop)
| Load (W) | AWG 18 | AWG 16 | AWG 14 | AWG 12 | AWG 10 |
|---|---|---|---|---|---|
| 5 | 28 ft | 45 ft | 71 ft | 113 ft | 180 ft |
| 10 | 14 ft | 22 ft | 36 ft | 57 ft | 90 ft |
| 20 | 7 ft | 11 ft | 18 ft | 28 ft | 45 ft |
Worked Example
Goal: Two 5 W heads on one branch (10 W) at 12 V using AWG 16. From the 12V table, 10 W @ AWG 16 ≈ 90 ft one-way. If your route is 120 ft one-way, you’re over the 5% target—either upsize to AWG 14 (≈ 143 ft) or step up to 24 V (10 W @ AWG 16 ≈ 359 ft). Always verify at the end of the 90-minute test.
Branch Design Tips
- Calculate segment-by-segment on shared branches using the maximum simultaneous load on each segment.
- Favor home runs to farther heads to keep shared current low on long segments.
- Mind connections: every splice adds resistance—keep them tight and minimal.
- When in doubt, step up wire gauge or voltage and confirm with a live 90-minute test.
Remote-head sizing note: Use these tables alongside the remote-capable exit sign combo sizing guide to keep farthest-head voltage in range.
Beam selection note: Once conductor distance is acceptable, use the MR16 vs PAR36 beam guide to decide whether a narrow throw or wider flood pattern fits the area.
Use these wire-gauge tables alongside the remote head compatibility matrix to verify voltage match, spare watts, and farthest-head voltage.
FAQs: Wire Gauge & Distance
Are these distances conservative?
They’re practical estimates for planning with ~5% drop and copper at room temperature. Battery sag, temperature, and connections can reduce brightness—test live and leave margin.
Do these tables handle multiple heads?
Yes—use the total branch wattage for the portion of the run you’re evaluating. On shared segments, use the load that flows through that segment.
Should I choose 24V just for distance?
Often helpful for long runs or higher loads. But for short runs, 12V is fine and simpler for inventory. See the companion post 12V vs 24V for long runs.