1. Why voltage drop becomes a facade failure

For the same wattage, a lower-voltage system carries more current than a higher-voltage system. More current creates more cable drop and heat because conductor loss follows I²R. Addressable RGB/RGBW loads also change with content: a dark animation may pass commissioning while a full-output white scene exposes weak feeders, connectors or supplies.

MEAN WELL specifically warns that extending the DC cable can create insufficient voltage at the lamp and may affect operation [S3]. This makes cable length part of the luminaire system—not a late installation detail.

2. The calculation model

Here L is one-way cable length, A is conductor cross-section, and ρ is copper resistivity. Infineon's application note uses 0.0175 Ω·mm²/m and explains why both positive and return conductors are included [S2]. Actual resistance changes with conductor construction and temperature; use the approved cable data for released drawings.

3. Worked case: one long feeder

Project assumptions—not a LIKELIGHT product guarantee: 10m of the published 19.2W/m maximum configuration [S1], 24V nominal, a 15m one-way copper feeder and 2.5mm² conductors. Treating the entire load as a far-end load gives a conservative feeder comparison:

• Load power = 10m × 19.2W/m = 192W
• Current = 192W ÷ 24V = 8A
• Loop resistance = 2 × 0.0175 × 15 ÷ 2.5 = 0.21Ω
• Drop = 8A × 0.21Ω = 1.68V or 7.0%
• Estimated load-terminal voltage = 22.32V
• Cable loss = 8² × 0.21 = 13.44W

This does not prove the product will fail at 22.32V; the permitted input range is 待确认. It proves that the installer cannot assume the far end still receives 24V.

4. Compare cable size and branch design

The third option supplies two 5m/96W zones. It reduces current per branch and loop length. It also adds distribution boxes, fuses, connectors and commissioning points, so it is an engineering trade-off rather than a free improvement.

5. How to set an allowable drop

There is no safe universal percentage for every addressable LED product. The released limit must come from the approved luminaire input range, controller/IC behavior, connector and cable tolerances, ambient temperature and the visual acceptance test. A project may use 3% as an internal design target, but that is an engineering assumption until the manufacturer and project engineer approve it.

Do not raise an adjustable supply above its permitted output merely to hide an undersized cable. Some supplies allow adjustment, others do not, and every luminaire still has a maximum input rating. Follow the exact supply and luminaire documentation.

6. Power injection and topology

Each branch should be documented with load, cable type, one-way length, fuse, connector rating, injection point, measured no-load voltage and measured full-load far-end voltage. The MEAN WELL installation manual requires secondary cable current rating to meet the supply rating and points to model-specific derating [S4].

7. Product and system evidence

8. When not to use one centralized 24V feed

• When calculated branch drop exceeds the approved project limit.
• When one supply or cable fault would black out an unacceptable facade area.
• When conductor size, conduit fill or connector current becomes impractical.
• When the far-end voltage cannot be measured under worst-case content.
• When cable-loss heat and cabinet derating have not been assessed.

9. When not to add injection blindly

• Do not connect separate power supplies together unless the manufacturers and electrical design explicitly permit the topology.
• Do not inject power without branch fusing and polarity documentation.
• Do not assume all grounds, data references and isolation schemes are interchangeable.
• Do not place inaccessible junctions behind sealed facade elements.

10. Commissioning test

1. Record source voltage with the branch disconnected and connected.
2. Run the approved maximum-load scene, normally including full-output white where applicable.
3. Measure the beginning, intermediate injection point and far end.
4. Check brightness/color uniformity, pixel stability, connector temperature and PSU status.
5. Repeat at the expected ambient condition or apply documented derating.
6. Save results against branch IDs and as-built drawings.

11. Evidence ledger

12. FAQ

Is 24V always better than 12V?

For equal wattage, 24V draws half the current of 12V, which helps feeder drop, but product compatibility and segment design still control the decision.

How far can a 24V cable run?

No fixed distance applies. Calculate from current, loop length, conductor resistance and approved terminal-voltage limit.

Can I solve drop by increasing PSU voltage?

Only within the documented adjustment and luminaire input limits. Cable redesign or additional injection is usually the safer design discussion.

Why test full white?

For RGB/RGBW systems it is commonly a high-load state and can reveal voltage and thermal weaknesses hidden by darker content; confirm the actual maximum-load pattern with the product supplier.

Who authored this article?

Author: LikeLight Tom, Operations. Technical reviewer: 待确认.