Class 2, SELV, and the Safety Labels That Decide Where a Driver Can Go

The stickers on a driver's housing carry more than branding; they define the electrical limits of the output and therefore where the driver can legally and safely be installed. Class 2, SELV, Class I and Class II are distinct concepts that are easy to blur, and each has a different consequence for the installer.

SELV, safety extra-low voltage, is a property of the output circuit. Under the IEC framework, a SELV circuit is isolated from the mains and limited to a touch-safe voltage, at most 60 V DC or 42.4 V peak AC in normal operation, with the isolation provided by a transformer. A 24 V isolated driver's output is a SELV circuit: touching it while grounded completes no dangerous current path back to the mains. The isolation, not just the low voltage, is what makes it safe, because a non-isolated 24 V output is not SELV even though its DC value is low.

Class 2 is a North American concept, defined in the National Electrical Code through UL 1310 for power supplies and UL 8750 for LED equipment. A Class 2 output is limited in voltage, current, and power: no more than 60 V DC, with the power limited to 100 VA and current to 8 A in the commonly cited ceiling. The point of Class 2 is that the output cannot deliver enough energy to start a fire or cause injury under fault conditions, so the wiring behind it is subject to fewer code restrictions. Most waterproof 24 V drivers for strip lighting are designed to stay under the 100 VA Class 2 ceiling, which is why 96 W and 100 W appear so often as the top of a family.

Class I and Class II describe the insulation scheme of the whole equipment, not the output voltage. Class I equipment relies on a protective earth connection as part of its shock protection; Class II equipment uses double or reinforced insulation and does not require an earth. A waterproof driver with a metal housing that is bonded to earth and depends on that earth for safety is Class I; one with a fully insulated enclosure and no earth terminal is Class II. Neither is the same as Class 2, and the coincidence of names is a persistent source of confusion on project files.

The practical consequence is that the safety class decides the installation rules. A Class 2 output lets an installer use the low-voltage wiring rules, run the output cable without conduit in many jurisdictions, and terminate it in accessible locations. A non-Class 2 or non-isolated output may force the output to be treated like a mains-level circuit, with enclosed wiring and restricted access, regardless of the 24 V reading on the meter. That difference changes the whole installation cost and method.

When a datasheet lists both UL 1310 Class 2 and an isolated SELV output, it is telling the installer that the accessible low-voltage wiring is both touch-safe and energy-limited, which is exactly what outdoor strip lighting wants. Buyers who see only the 24 V and assume low risk should read the isolation and Class 2 claims before routing the output cable, because the label, not the voltage, governs the code.