Cable Glands and Sealing: Where Waterproof Drivers Actually Fail

A waterproof LED driver can pass every test in the factory and still fail in the field, and the point of failure is almost always the cable entry. The driver's IP67 rating is only as good as the seal around the wire that enters it. Understanding cable glands is understanding where the waterproof claim is really made.

An IP67 rating on the housing is tested with the enclosure sealed as shipped. Once the installer passes a cable through the wall and tightens the gland, the rating of the whole assembly depends on that gland being correctly fitted. A gland that is undertorqued, a cable with a jacket that does not match the gland's bore, or a wire that is stripped too long so the gland grips the conductors instead of the jacket, all compromise the seal. Water then enters slowly, and the driver fails weeks or months later, not on day one.

The standard IP67 cable entry is a compression gland. The cable passes through a rubber seal, and a threaded cap is tightened to compress that seal around the cable's jacket. The gland's bore is sized for a specific cable diameter range; using a cable outside that range means the seal cannot close properly. For outdoor use, the gland should also be strain-relieved, so that pulling on the cable does not move it and loosen the seal over time.

There are alternatives worth knowing. A connectorised entry, where the driver ships with a factory-sealed plug and socket, removes the field decision entirely: the installer connects to a mating connector rather than passing wire through the housing. This is the most reliable method because the seal is made in the factory and tested once. A hard-wired entry with a proper compression gland is nearly as reliable if the gland is selected and torqued correctly, but it moves the responsibility to the installer.

The most common field mistake is sealing a gland with silicone or tape instead of relying on the compression mechanism. Silicone is not a substitute for a gland that fits; it dries, cracks, and provides no strain relief. Equally common is over-stripping the cable so the gland compresses the bare conductors, which both seals poorly and risks shorting the strands together. The rule is simple: the gland must grip the jacket, the jacket must be the right diameter, and the gland must be tightened to the manufacturer's torque, not just until it feels snug.

A buyer can infer the sealing quality from the design. A driver with properly sized, factory-tested compression glands, or a connectorised option, has addressed the failure point at the design stage. A driver with a generic gland that requires exact cable selection is more demanding in the field. For a product installed by a busy electrician on a ladder, the connectorised or well-glanded option is the one that keeps the waterproof claim intact in the real world, not just on the datasheet.

There is also the question of the cable itself. The jacket material matters as much as the gland: a PVC jacket softens and creeps under compression, while a cross-linked or rubber jacket holds its shape and keeps the gland's seal tight over years of temperature cycling. An installer who replaces the specified cable with a thinner or stiffer one can make a correctly sized gland fail. The complete seal is a system of the gland, the torque, the jacket, and the strain relief, and weakening any one of them lets the others fail in turn. Buying a driver whose gland is matched to a standard cable diameter, and installing that exact cable, is what keeps an IP67 rating meaningful after the first hot summer and cold winter.