Specifying an Outdoor Cabinet: IP Rating Plus Everything Else

An IP66 cabinet installed outdoors can still fail within a year, and the failure is usually not water ingress from rain but condensation, heat and UV.

Condensation

A sealed cabinet heats during the day and cools at night. Moisture trapped at installation condenses on the coldest surface, usually the metal backplate, and runs down onto the electronics. A breather membrane and a desiccant sachet, replaced on schedule, solve most of it.

Solar load

Internal temperature can reach 25 K above ambient in direct sun. Use a sun shield, light colours, and ventilation with filters where the IP rating allows. A fan that pulls unfiltered air defeats the IP rating entirely.

UV and salt

Gaskets and cable jackets degrade in UV unless specified for outdoor use. In coastal sites, stainless fixings and a corrosion resistant enclosure matter more than the IP number. Specify the material, not just the rating.

Installation

Mount with a slight forward tilt so water runs off, keep cable entries at the bottom with drip loops, and never drill a new hole in the field without sealing it to the same standard as the factory entries.

Related technical notes

• Simulating Rain: When IPX3 or IPX4 Is the Right Model
• When an IP Test Fails: A Structured Way to Find the Path
• Which Standard Applies: IEC 60529 and Its Product Relatives