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IP Classification

Electric motor IP (ingress protection) classification is a measure of the capacity of the motor to resist ingress of dust and of water. Objects, dust, or water may enter the motor providing they cannot have any detrimental effect upon its operation.

Two numbers follow the letters IP. The first number defines resistance to dust and the second to water.

The following examples are fairly typical classifications of motors used to drive general-purpose fans. The descriptions are abbreviated.

Protection Class Object Protection Water Protection Fans within Axair Range
IP20 Solid objects over 12.5mm Non-protected
IP23 / IP24 Solid objects over 12.5mm IPx3 : Spray at angle up to 60° Vertical
IPx4 : Splashed water
IP44 Solid objects over 1mm Splashed water
IP54 Dust Resistant Splashed water
IP55 Dust Resistant Hosed water
IPW55 Dust Resistant Rain water
IP65 Dust exclusion Hosed water

IP55 in particular is a very misunderstood category because it is often sold as being ‘as good as weather-protected’. Unfortunately no motor manufacturer will accept a warranty claim for damage to an IP55 motor that has been installed outdoors without a ventilated rain cover. The reason is that rain water, or melting snow and ice, has time to penetrate unsealed gaps and assembly spigots, whereas hosed water is only applied for a short wash-down period and the motor dries quickly.

Examples of weather-protected fans
Corrosion resistant centrifugal fan with weather pedestal Fan filter kit type FPF with stainless steel cover Roof fans

IP55 does not necessarily imply sealing of the motor external surface, it can mean sealing the bearings, and totally protecting motor windings and all connections with resin, a plastic cover, or both. Water is then permitted to enter the motor but can do no harm.

Examples of motor protection through encapsulation
External rotor motor winding without protection (For IP44 protection once complete with rotor) External rotor motor winding encapsulated with resin for full IP55 protection

External rotor motors, although only of IP44 or 54 splashed water protection class, do have the facility for draining any water that may enter the motor through the annular gap between the rotor and the motor backplate, or through a hole at the opposite end of the rotor. This is only recommended for types of external rotor motor that have had their internal surfaces corrosion protected.