Channel-letter drawings fail most often when three voltages collapse into one line: site AC, driver input, and module DC. This materials note separates 12 V DC versus 24 V DC LED modules, adds Class 2 headroom language buyers can paste, and keeps crate AC aligned with the export build sheet—without claiming that finished letters are listed products by default.
Three voltages on every drawing
Write them as separate callouts. Site AC is the building power at the destination: European Union, United Kingdom, and Australia use 230 V / 50 Hz; the United States uses 120 V / 60 Hz (277 V only when the quote says so). Driver input matches that mains choice and the driver’s wet or damp rating. Module DC is the constant-voltage bus inside the letters—almost always 12 V or 24 V for channel-letter modules. Never mix 12 V and 24 V modules on one secondary circuit. Singapore and Malaysia follow the 230 V family; Japan 100 V and Korea 220 V must be named per job because the public export sheet carries no default JP/KR stencil.
What 12 V DC buys
Twelve-volt module families remain the common stock for many channel-letter shops: wide module catalogues, familiar Class 2 practice, and short DC runs inside compact letters. Trade guidance often discusses Class 2 secondary channels near sixty watts at 12 V—always confirm the module and driver datasheets for the job rather than treating that figure as a universal code. Smaller capitals, short raceway jumps, and dense module layouts that stay within one secondary channel are natural 12 V fits. Voltage drop still matters: long thin conductors on a 12 V bus waste copper and dim the far letters first.
What 24 V DC buys
Twenty-four-volt modules carry half the current for the same wattage, which helps longer DC runs, fewer parallel feeds, and sometimes fewer power supplies on wide wordmarks. Class 2 discussions often cite a higher watt ceiling near ninety-six watts at 24 V than at 12 V; again, datasheet and local practice win over magazine round numbers. Large halo bars, long linear accents, and multi-letter strings that would otherwise need many 12 V supplies are typical 24 V candidates. The bus choice does not automatically make the face brighter or more efficient—chip design, thermal loading, and optical path decide luminous results more than the nominal DC voltage.
Efficiency myth and thermal reality
Industry education pieces have long warned that “24 V is more efficient” is an oversimplification. A well-designed 12 V system can outperform a poorly heatsinked 24 V layout. Spec drawings should call out module series, colour temperature, IP intent for outdoor modules, estimated total watts, and ambient derating—not only the bus voltage. Hot façades and sealed cans need driver headroom and module spacing notes so lifetime claims remain honest.
Driver selection language for RFQs
Ask for Meanwell-class or a named brand when the job requires it; state wet or damp location rating; choose remote ventilated enclosure versus in-raceway mounting; keep roughly twenty to thirty percent watt headroom; and derate for high ambient. Constant-voltage supplies feed most channel-letter module strings; constant-current products belong to different optical systems and should not be substituted quietly. Cable gauge and maximum DC run length belong on the same sheet as supply count so installers do not discover dim end letters on site.
Compliance wording that will not bounce a materials post
It is appropriate to request UL-recognized or listed modules and drivers when the destination job needs them. It is not appropriate to claim that the assembled channel letters are UL 48 listed, CE marked, or RCM certified by default, or that the factory is listed as such. Module marks are not assembled-sign listings. Local listing paths, where required, stay with the destination electrician and the technical file quoted for that job. Outdoor IP language should target the complete letter or cabinet enclosure under IEC 60529 thinking—doors, gaskets, glands, and faces—not a module badge alone.
Drawing callouts checklist
- Module DC voltage: 12 V or 24 V (single family per circuit).
- CCT, IP intent, estimated total watts, supply count.
- Max DC run length and wire gauge note; spare modules quantity.
- Driver: brand class if specified; wet/damp; remote vs raceway; headroom percent.
- Site AC: EU/UK/AU 230 V 50 Hz or US 120 V 60 Hz (or named JP/KR).
- Crate stencil matches chosen AC; pack list and QC photos as required for the Incoterm.
Tie-back to export crates
ACPSigns’ public export build sheet carries the AC defaults and reminds buyers that module recognition is not a finished-sign certificate. Product pages for illuminated letters quote AC input plus DC 12/24 at the letter for each job. Put both on the drawing: the crate travels with the mains mark the destination needs; the bill of materials carries the DC family the modules require. That split keeps RFQs clear for Shenzhen-origin fabrication and for US or EU fill-in shops comparing domestic wholesale sets to export crates.
When you revise an older drawing that only said “LED channel letters, outdoor,” expand it into the three-voltage block above before the next quote round. Buyers who paste Class 2 watt limits, run-length notes, and destination AC in the same email reduce change orders after acrylic faces are already cut.