Enclosure class states the degree to which an electrical enclosure, such as a motor, is protected against the intrusion of solid objects and water.
For electric motor enclosure types, the enclosure class is expressed as ‘IP’ followed by two digits (see table). The two digits indicate the protection against solid objects and water, respectively.
Example: An electrical socket rated IP33 is protected against solid objects bigger than 2.5 mm, i.e. wires, tools, etc. The socket will not be damaged or become unsafe if it is exposed to water spray falling at an angle of 60° from vertical.
IP33 is of a higher standard then IP2X that is the typical minimum requirement for indoor use. ‘X’ is used when there is no protection rating for the criterion concerned, in this case water intrusion.
In some situations a lower IP class may be more suitable than a higher IP. For example, IP 44 motors can be more suitable than an IP 55 motor in a damp environment where condensed vapor can form in the stator housing. Drain holes in an IP 44 motor allow the moisture to drain out of the stator housing, which would not be possible in an IP 55 motor.
The electric motor enclosure type for Grundfos motors is noted on the motor nameplate.
”IEC 60034-5 Degrees of protection provided by enclosures (IP Code)” gives a full overview of enclosure classes.