Match the output voltage first
Confirm whether the LED load is rated for 12V DC or 24V DC, then select a constant-voltage supply with the same output. A voltage mismatch can damage components or prevent them from operating correctly. The AC input range must also be appropriate for the supply installation.
Do not choose a driver from physical size alone. Read the label or data sheet and confirm output voltage, maximum output current, rated power and environmental protection.
Calculate the connected LED load
For LED modules, multiply the module wattage by the number of modules. For LED strip, multiply watts per metre by the installed length. Add separate circuits together only when they are genuinely supplied by the same unit.
This is the LED load before operating headroom. Confirm the module's actual rated wattage rather than relying on a similar-looking product.
Allow appropriate operating headroom
Running a power supply continuously at its absolute maximum can reduce tolerance for heat, component variation and future changes. A common project approach is to operate at no more than roughly 80% of rated capacity unless the manufacturer specifies otherwise.
The next suitable rated unit above 90W would be considered, subject to the manufacturer's loading, derating and installation guidance.
This is a selection example, not a substitute for the product data sheet or electrical design. High ambient temperatures or restricted ventilation may require additional derating.
Match the enclosure to the environment
State whether the supply will be indoors, inside a sign cabinet, in a roof space, outdoors or exposed to moisture. An IP-rated unit may be required, but the installation must still provide suitable drainage, cable entry protection, heat management and service access.
Check the permissible ambient temperature and mounting orientation. Enclosing a supply in a small unventilated space can materially change its operating conditions.
Plan circuits, cable length and control
Long low-voltage cable runs can create voltage drop, uneven brightness and excessive current in the conductors. Larger installations are often divided into shorter correctly protected circuits. Confirm maximum module run lengths and cable sizes with the product documentation and installer.
If the system requires dimming, switching or colour control, confirm compatibility before purchasing. Not every supply supports every control method.
Protect the installation
Mains wiring, earthing, circuit protection and final connection should be completed by a competent person in accordance with applicable requirements and the manufacturer's instructions. The supply must remain accessible for inspection and replacement without creating a hazard.
- LED load voltage: 12V or 24V DC
- Total module count or strip length
- Watts per module or watts per metre
- Indoor, sheltered or exposed location
- Ambient temperature and ventilation
- Dimming or control requirement
- Cable-run lengths and circuit layout
- Preferred brand or model, if replacing an existing unit
LED power-supply FAQs
Can I replace a 100W supply with a larger wattage?
A higher capacity does not force extra power into a correctly matched constant-voltage load, but voltage, wiring, protection, physical fit and product requirements must still be checked.
Why does a 12V installation dim at the far end?
Voltage drop, excessive run length, undersized conductors or overloaded circuits are common causes. The system should be measured and assessed before components are replaced.
Does an outdoor-rated power supply need an enclosure?
That depends on the exact rating, mounting position, connectors and exposure. Follow the manufacturer’s instructions and do not assume the rating alone covers every installation condition.