SEPA DC fans are equipped with protected ball bearings (Type ZZ) and electronics protected by a labyrinth against the direct effect of humidity so that its influence on service life and reliability is minimized.
The standard information described in the specifications always refers to a mean humidity of 15-65% RH, uncritical test values to 15-75% RH. This information determines the environmental conditions defined for testing so that their influence is minimised as far as possible.
The limit values permitted when in use are limited at the lower end by the increase of possible ESD interference and at the top end by the development of drops of condensation. A fan installed in a device is normally completely insensitive to ESD interference. At the upper end, only the formation of condensation needs preventing. Due to the insignificant heating of the fan during operation, condensation cannot form even when humidity is almost 100%.
As mentioned above, the permitted humidity range during operation can be defined at 10-98% RH, if there is no possibility of condensation forming.
Conditions are different if the fan is taken from a cold to a warm room, e.g. when transporting devices from a non-heated storeroom to a heated room. Under certain conditions, slight humidity may cause the formation of condensation, however the drops will form mainly on the outside of the housing.
The fan frame and housing are absolutely waterproof. A temporary formation of condensation that seldom occurs will not negatively affect the performance of the fan.
Slow changes in temperature in the area of operation of the fan will not have an affect as long as the fan and surrounding air have approximately the same temperature. This also applies to high humidity of approx. 98% RH, without formation of mist.
If mist is formed continuously due to high humidity, this can reduce the service life of fans, in particular when the steam contains aggressive media (e.g. acids). This is also possible if the fan never runs or only seldom runs.
Mechanical filters do not provide additional protection against excess humidity and the formation of mist.