12V vs 24V for Remote Heads: Distance, Voltage Drop & Wire Size

Why Voltage Matters

Remote heads run on low voltage from a remote-capable host unit. At a given wattage, higher voltage means lower current, which reduces drop on long conductors. That’s why 24V systems often carry the same load farther than 12V systems before dimming becomes noticeable. For placement/aiming guidance, see the remote head spacing guide.

Voltage-Drop Basics (Simple Math)

Three quick steps get you close enough for planning:

1. Current (A): I = P / V   (P = total watts on the run; V = system voltage)
2. Estimated resistance: Use your conductor’s ohms per 1000 ft from a standard table (Cu). Multiply by round-trip length.
3. Drop (V): Vdrop = I × R   → Aim for roughly ≤ 5% of system voltage at the far head under emergency load.

Need ready-to-use tables? See wire gauge & distance tables (AWG 18–10).

How Voltage Affects Distance

• Same load, higher voltage → less current: Halving current roughly halves the drop for the same wire and length.
• Practical impact: 24V often doubles your workable distance vs 12V before reaching a 5% drop threshold (ballpark; verify with your actual run and wire).
• Shared circuits: On multi-head branches, calculate with the maximum simultaneous load on each segment.

Choosing Wire Gauge for ~5% Drop

1. Compute current for the branch (I = P/V).
2. Estimate round-trip length (panel → head → back).
3. Pick a gauge and check drop; if above ~5%, move to thicker copper (e.g., AWG 16 → 14 → 12).
4. Favor short home-run branches to the far heads; avoid daisy-chaining long strings when possible.

For long exterior runs or high-watt heads, 24V + thicker wire is often the cleanest solution.

When to Choose 24V

• Long runs to exterior doors, large lobbies, or high-ceiling spaces.
• Higher total remote load on a branch (multiple heads or higher-watt heads).
• Voltage-sensitive optics where dimming at the tail end would create dark spots.
• Future expansion—leave headroom for one more head without re-pulling conductors.

When 12V Is Still the Right Choice

• Short runs with modest loads (e.g., a couple of low-watt LED heads close to the host).
• Retrofits where existing conduit or terminations favor smaller conductors and short distances.
• Inventory/service consistency if your site standardizes on 12V and runs are well within limits.

Worked Examples

Example A — 12V corridor run, single head

Load: 5 W LED head. Voltage: 12 V → I = 5/12 ≈ 0.42 A.
Length: 120 ft one-way (round-trip 240 ft). Wire: AWG 16 (approx R ≈ 4.0 Ω/1000 ft).
R (run): 4.0 × 0.240 = 0.96 Ω → V_drop ≈ 0.42 × 0.96 = 0.40 V (≈3.3%). Pass.

Example B — 12V, two heads on a long branch

Load: 2 × 5 W = 10 W → I = 10/12 ≈ 0.83 A on shared segment.
Same wire/length as A → V_drop ≈ 0.83 × 0.96 = 0.80 V (≈6.7%). Borderline. Fix by upsizing to AWG 14 or stepping to 24V.

Example C — 24V upgrade on the same geometry

Load: 10 W at 24 V → I = 10/24 ≈ 0.42 A (half the current). Using AWG 16, same length:
V_drop ≈ 0.42 × 0.96 = 0.40 V → as a % of 24 V ≈ 1.7%. Comfortable.

FAQs: 12V vs 24V Remote Heads

Is 24V always better than 12V?

No. 24V carries load farther on the same wire, but for short runs with small loads, 12V is perfectly fine and may simplify parts and service.

What drop limit should I use?

Designers often work to about 5% as a practical planning limit. Always verify illumination at the farthest head during the 90-minute test.

Do I need to upsize both voltage and wire?

Not necessarily. Try one lever at a time: thicker wire or higher voltage. Use both only if needed by distance and load.