In this guide
Why the right LED module matters
Channel letters are three-dimensional fabricated letters — typically aluminium or steel — with a translucent acrylic face through which LED modules illuminate the letter from inside. Unlike flat panel lighting or strip applications, channel letters impose hard constraints on the LED modules installed within them: tight depth, curved internal profiles, and constant exposure to moisture and temperature variation.
Choosing the wrong module leads to predictable failures: too much wattage causes hotspots and melted acrylic faces; too little wattage produces dim, uneven illumination that looks unprofessional at night. Wrong IP rating causes early failure from condensation ingress. Wrong colour temperature results in a sign that doesn't match the client's brand.
The good news is that the specification process is straightforward once you understand five variables: wattage, brightness (lumens), colour temperature, IP rating, and module spacing. Master these and you can correctly specify any channel letter job, regardless of size or complexity.
Key specifications explained
When reviewing LED module datasheets, you'll encounter a consistent set of specifications. Here is what each means in practice for channel letter applications:
Wattage (W)
Power consumed per module. Determines heat output and run cost. Lower wattage ≠ lower brightness if lumens are optimised.
Lumens (lm)
Actual light output per module. The number that matters for visible brightness, not wattage alone.
IP Rating
Ingress protection against dust and moisture. IP68 is the professional standard for channel letters.
Beam Angle
How wide the light spreads. 170° is ideal for channel letters — it fills the letter depth evenly without hotspots on the face.
Wattage and brightness: what you actually need
The relationship between wattage and brightness is not linear — a well-engineered module can deliver more lumens per watt than a budget alternative of the same power rating. The Glowfy GL K8 PRO, for example, delivers 120 lumens from just 1.2W — a lumen efficacy of 100 lm/W, which is on par with premium commercial fittings.
Depth rules the wattage decision
The depth of the channel letter (the distance between the back plate and the acrylic face) is the primary driver of which module wattage is appropriate:
| Letter Depth | Recommended Module | Wattage | Output | Notes |
|---|---|---|---|---|
| Under 40 mm | GL K2 PRO | 0.72W | 70 lm | Shallow halo letters; avoid hotspotting |
| 40 – 80 mm | GL K8 PRO | 1.2W | 120 lm | Standard depth; most common application |
| 80 – 150 mm | GL K8 PRO | 1.2W | 120 lm | Increase spacing; letters fill well |
| Over 150 mm | GL K8 PRO ×2 rows | 1.2W ea. | 120 lm ea. | Run two rows; stagger positions |
A module placed too close to a shallow acrylic face creates a visible hot-spot — a bright circular patch visible through the sign face. Reducing module wattage or increasing spacing between modules solves this. If you cannot increase spacing due to letter geometry, use a lower wattage module.
Colour temperature: matching the brief
Colour temperature is measured in Kelvin (K) and describes the warmth or coolness of white light. For channel letter signage, you will typically be choosing between two options: Cool White and Warm White.
Cool White — 6500K
Produces a bright, clean white with a slightly blue-white cast. Standard choice for retail, commercial and corporate signage. Maximises perceived brightness, reads clearly at distance, photographs cleanly.
Best for
- Retail and commercial fascia signs
- Corporate and office building signage
- Service business signage
- Any application where maximum perceived brightness is needed
Warm White — 3000K
Produces a warm, amber-tinted white. Lower perceived brightness than Cool White at the same lumen output, but creates a premium, inviting atmosphere. Preferred where brand warmth is important.
Best for
- Hospitality: restaurants, hotels, bars
- Heritage and traditional brand signage
- Luxury retail environments
- Residential development signage
Never mix colour temperatures within a single sign or set of letters. Even a small difference in Kelvin between batches creates a visible tonal mismatch. Order all modules for a job from the same batch where possible, and always request the same colour temperature throughout.
IP rating: why IP68 is the professional standard for channel letters
The IP (Ingress Protection) rating describes a module's resistance to solids and liquids. The two digits represent dust protection (first digit) and water protection (second digit). For channel letter signage — whether indoor or outdoor — IP68 is the correct specification.
| IP Rating | Dust | Water | Suitable for Channel Letters? |
|---|---|---|---|
| IP20 | Partial | None | Indoor only. Not suitable. |
| IP44 | Partial | Splash-proof | Very limited outdoor protection. |
| IP65 | Total | Dust-tight. Jets | Better, but condensation still penetrates. |
| IP67 | Total | Immersion 1m/30m | Acceptable for sheltered outdoor signs. |
| IP68 | Total | Continuous submersion | Professional standard. Recommended. |
Even for indoor signs, IP68 is strongly recommended. Temperature cycling between day and night causes condensation to form inside letter cavities. Over time, non-sealed modules fail due to moisture contact with the PCB. An IP68 module eliminates this failure mode entirely.
All Glowfy LED modules are IP68 rated as standard — not as a premium option. This is a baseline requirement, not a selling point.
Module spacing and layout
Correct module spacing is critical to achieving uniform illumination across the acrylic face. The 170° beam angle of a Philips 2835 module means light spreads widely within the letter cavity — but there are still limits. Space modules too far apart and you get visible dark patches between them.
The spacing rule of thumb
For GL K8 PRO modules in standard-depth channel letters (50–80mm), place modules at 60–80mm intervals along the internal perimeter of the letter. For GL K2 PRO in shallow letters, reduce to 50–60mm intervals.
| Module | Depth | Spacing | Expected Result |
|---|---|---|---|
| GL K2 PRO | <40mm | 50–60mm | Uniform, no hotspots |
| GL K8 PRO | 40–80mm | 60–80mm | Bright, even illumination |
| GL K8 PRO | 80–150mm | 80–100mm | Good fill; some fall-off at corners |
At corners and tight curves, reduce spacing by 20–30% to compensate for the shorter line-of-sight distance to the acrylic face. For tall, wide letters — a large capital H or M, for example — place an additional module in the geometric centre to eliminate a potential dark patch.
The adhesive backing on Glowfy modules is industrial-grade — it will bond directly to clean aluminium without additional fixings on standard installations. For very hot environments (south-facing outdoor signs in direct sunlight), supplement with mechanical fixings through the module mounting hole.
Power supply sizing
All Glowfy LED modules run on 12V DC constant voltage. Selecting the right power supply is a straightforward calculation — but the 20% headroom rule is non-negotiable.
Power calculation method
Step 1: Count total modules across all letters
Step 2: Multiply × 1.2W (GL K8 PRO) or × 0.72W (GL K2 PRO)
Step 3: Add 20% headroom: total W × 1.2
Step 4: Select next power supply size up from result
Example: 40 × GL K8 PRO modules = 40 × 1.2W = 48W. With 20% headroom = 57.6W. Select a 60W power supply.
Running a power supply at or above 80% of its rated capacity shortens its lifespan significantly. The 20% headroom rule ensures the supply operates comfortably within its thermal limits, extends its service life, and prevents voltage sag that causes colour shift at the far end of long module runs.
For sign installations with multiple letters distributed across a fascia, you can wire all letters to a single supply (if total wattage allows) or use one supply per letter set — whichever is tidier for the cable run. Always use waterproof junction boxes for any connections outside the letter cabinet.
Glowfy LED modules: full range
Glowfy stocks four professional LED module product lines across two beam-angle categories. The GL K8 PRO and GL K2 PRO use Philips 2835 chips with a 170° wide beam — ideal for front-lit and internally illuminated channel letters where broad, even backfill illumination is required. The GL 4030 and GL 4035 use SMD 3030 chips with a directed 45°×15° asymmetric beam — purpose-built for halo-lit reverse channel letters and fascia panels where light is projected onto a backing surface.
| Specification | GL K8 PRO | GL K2 PRO |
|---|---|---|
| LED Chip | Philips 2835 | Philips 2835 |
| LEDs per Module | 3 | 2 |
| Voltage | 12V DC | 12V DC |
| Wattage | 1.2W | 0.72W |
| Lumens | 120 lm | 70 lm |
| Beam Angle | 170° | 170° |
| IP Rating | IP68 | IP68 |
| Dimensions | 69 × 19 × 10.5 mm | Compact |
| Wire Length | 74 mm | Standard |
| Pack Size | 20 modules | 20 modules |
| Warranty | 5 years | Standard |
| Best For | 40–150mm depth | Under 40mm depth |
GL K8 PRO
Most popular1.2W · 120lm · IP68 · 170° · Philips 2835 · For 40–150mm depth letters
View productGL K2 PRO
Shallow letters0.72W · 70lm · IP68 · 170° · Philips 2835 · For under 40mm depth letters
View productGL 4030
Halo / directed1.5W · 145lm · IP65 · 45°×15° beam · SMD 3030 · Halo-lit channel letters & fascia
View productGL 4035
High output halo2W · 190lm · IP65 · 45°×15° beam · SMD 3030 · High-output halo & large fascia panels
View productProfessional installation tips
Correct specification is only half the job. The way modules are installed determines the final quality of the finished sign. Follow these professional practices on every job:
Clean the substrate before bonding
Wipe the interior aluminium surface with IPA (isopropyl alcohol) before applying modules. Any dust, oil or release agent will prevent the adhesive from bonding correctly. Allow to dry for 30 seconds before pressing the module down.
Run the wiring before installing modules
Plan your wiring route first. Thread wires through the back plate before pressing modules into position — retrofitting wires around bonded modules causes unnecessary handling and risks delamination.
Test before sealing
Power up the completed letter before fitting the acrylic face. Identifying a failed module or a cold solder joint at this stage takes minutes. Finding it after the face is glued on takes much longer.
Allow adhesive cure time
Industrial acrylic adhesive reaches full bond strength after 24–48 hours. Avoid rough handling or vibration immediately after installation. If fitting a face same-day, use supplementary clips on the first letter until the adhesive sets.
Use consistent wire lengths between modules
Inconsistent wire lengths between series-connected modules can cause voltage variation along the run. Keep inter-module connections as short and consistent as possible, especially on long runs of more than 20 modules.
Frequently asked questions
What wattage LED module is best for channel letters?
For standard-depth channel letters (50–80mm), the GL K8 PRO at 1.2W per module is the professional standard. For shallow letters under 40mm, use the GL K2 PRO at 0.72W to avoid hotspotting on the acrylic face.
Do I need IP68 for outdoor channel letters?
Yes. IP68 provides complete protection against moisture ingress including condensation — the most common cause of premature LED failure in channel letters. Even for indoor signs, IP68 is recommended because temperature cycling creates condensation inside letter cavities over time.
What colour temperature should I use for white channel letters?
Cool White 6500K is the standard for commercial and retail signage. Warm White 3000K is preferred for hospitality, luxury retail and heritage brand applications. Never mix colour temperatures on the same job.
How many LED modules do I need per channel letter?
Count the total internal perimeter of the letter in millimetres and divide by your chosen spacing (60–80mm for GL K8 PRO). A capital letter 150mm tall typically requires 6–10 modules depending on its shape and internal geometry.
Can I connect multiple channel letters to one power supply?
Yes. Calculate total wattage (modules × 1.2W for GL K8 PRO), add 20% headroom, then select the next power supply size up. For example, 40 modules = 48W × 1.2 = 57.6W → choose a 60W power supply.
Trade professionals
Open a Glowfy Trade Account
Sign makers and shopfitters with a Glowfy trade account get access to volume pricing, net-30 payment terms, dedicated account management and priority stock allocation — including on GL K8 PRO, GL K2 PRO, GL 4030 and GL 4035 modules.
Need help specifying your job?
Our technical team is available Monday–Friday, 8:30am–5:30pm. Call, email or use the contact form.