The short answer
Match the supply type and output voltage to the LEDs, calculate the full connected load, check the exact model’s continuous rating and temperature derating, then design accessible, protected wiring with acceptable voltage at the last module. Test the assembled sign at full load before closing it.
1. Write down the load before choosing a driver
Record each module or strip model, its rated voltage and power, the number of modules or metres, and any controller load. Most Glowfy K2 PRO and K8 PRO sign modules are specified for 12V DC constant voltage; a 24V LED strip needs a matching 24V supply. Do not treat a wattage match as permission to interchange 12V and 24V.
For example, 80 modules rated 1.2W consume 96W nominally. At 12V the nominal current is 8A. A 120W supply would be loaded to 80% at the stated ratings, but the final choice still depends on the model’s continuous rating, ambient temperature, derating curve, enclosure and inrush requirements. A “20% spare” rule is a planning aid, not a substitute for the datasheet.
2. Plan the power-supply location
Place the driver where its specified IP rating suits actual exposure, where heat can escape, and where it can be reached for inspection and replacement. A sealed sign cavity can become warmer than the outside air. Check the manufacturer’s installation instructions for mounting orientation, clearance, maximum case temperature and whether the driver may be covered by insulation.
In shallow channel letters, a driver mounted behind a translucent face can cast a visible shadow and occupy space needed for even light. A separate accessible housing or suitable sheltered position may make the sign easier to light and maintain. Route mains and low-voltage wiring according to the applicable instructions and have mains work carried out by a competent person.
3. Design the low-voltage distribution
At 12V, a given wattage draws twice the current of an equivalent 24V load. Long cable runs, undersized conductors and crowded connectors can create voltage drop and local heating even when the driver itself has spare capacity. Check the current rating of the cable, terminals and any controller. Keep polarity consistent and use protected, strain-relieved joints.
Split a large sign into suitable parallel branches following the module maker’s maximum modules-per-chain guidance. The number of physical output terminals does not necessarily mean separately regulated or individually protected circuits. Never parallel the outputs of two drivers unless their manufacturer explicitly allows it.
- Calculate current for each branch as watts divided by rated volts.
- Check the complete cable route, not merely the distance in a straight line.
- Provide any branch protection required by the installation design and manufacturer.
- Measure voltage under full load at the driver and at the farthest module.
4. Match weather protection to the installed position
An IP rating describes the enclosure’s tested resistance to ingress under defined conditions; it does not make unsealed cable joins, drilled holes or damaged glands waterproof. Specify the driver and every connection for the actual environment, including rain, wash-down, condensation and exposure to sunlight where relevant. Follow the manufacturer’s instructions for cable entry and drainage.
Keep the driver accessible without placing it where water pools. An IP67 module and a driver installed in a dry compartment can form a sensible system if every part is suited to its own location. Do not infer the driver’s rating from the LEDs’ rating.
5. Commission the sign before closing it
Run the complete sign at full brightness for a suitable observation period. Confirm the supply output remains within the LED specification and measure the most remote branch under load. Inspect every face for hotspots or dark areas, record the installed module count and driver model, and check case temperature against that model’s stated limit using the method in its datasheet.
Photograph the wiring and label accessible service points. A later technician should be able to identify voltage, capacity and branch layout without dismantling the whole installation. Recheck after dimmers or control gear are added: compatibility can change the installation’s behaviour.
Common symptoms and first checks
A systematic diagnosis saves replacing a sound driver unnecessarily.
| Symptom | Useful checks |
|---|---|
| Far end dimmer | Measure voltage under load at both ends; inspect cable length, section and branch layout. |
| Whole sign flickers | Check compatible dimming, overload, input supply, joints and driver protection behaviour. |
| One letter dark | Check that branch, polarity, connectors and individual modules before replacing the central supply. |
| Thermal shutdown | Check load, case temperature, mounting clearance and manufacturer derating. |
Frequently asked questions
Should I always run a driver at 80%?
No universal 80% requirement applies to every LED driver. It is a useful design margin, but the specific model’s continuous rating and thermal derating govern the installation.
Can I install a supply inside a channel letter?
Only where its dimensions, thermal limits, service access and wiring instructions allow it. In shallow letters it can also create a visible shadow behind the face.
Can an IP68 LED module use an indoor driver?
Only if the driver itself is located in a genuinely suitable dry environment and the full installation, including joints, meets its environmental requirements.
Does a larger supply cure dimming at the end of a run?
Not necessarily. Check voltage drop in the cable and modules under load. Additional parallel feeds or a revised branch layout may be needed.
Technical references
Use the current datasheet for the exact product you install. These manufacturer and standards resources explain the general principles.
Planning a professional LED installation?
Browse Glowfy power supplies, or send our Birmingham team the load specification and installation details for product guidance.