Frequent questions from customers and designers relate to the fact that fans can sometimes have two types of labels with different power P(W) and current I(A) ratings. This situation, although in line with best manufacturing practice, sometimes leads to confusion when commissioning equipment and issuing inspection reports.
The label on the fan casing
is supplied by the fan manufacturer and refers to the rated parameters of the fan. it respects the electrical parameters related to the allowed usable parts of the torque or power characteristics of the fan. The fan label shows the motor shaft power value adjusted by the efficiency value and the corresponding maximum current draw at the permitted operating point of the fan. (For more information on the permitted operating areas and shaft power flow for axial, radial and diagonal fans, see Ventilation and Air Conditioning, Chyský, Hemzal et al, page 200).
The label on the motor
is supplied by the motor manufacturer and contains only the maximum rated electrical parameters of the motor, unrelated to the actual fan power. Where motors are supplied from a standard power range, the power and current ratings on the fan case and motor may be significantly different. The motor nameplate shows, among other things, the maximum rated motor power and corresponding current values.
Sizing of the protection (except for Exe fans)
In terms of sizing the protection for fans for normal environments, the following cases may occur (the exception is Exe fans, where the protection is sized exclusively according to the parameters on the motor nameplate):
- the fan has only a label on the casing - the fan manufacturer manufactures its own motors and does not use standard asynchronous motors from power series, the protection is made according to the rated parameters indicated on the fan label
- fan has only a label on the motor - the fan uses a type motor from the standard power series, the sizing of the protection is done according to the nominal values indicated on the motor label
- fan has both a label on the cabinet and a label on the motor - the values of the electrical parameters on the motor label may be significantly higher than the values on the fan label, the fan does not use the full power capabilities of the motor, which is oversized due to the rough power series, the sizing of the protection is done according to the lower value on the fan label
- the fan has a label on the housing and a label on the motor - the values of the electrical parameters on the motor label may be lower than the values on the fan label, the fan, due to its design, cools the type motor with the air flow, which can be overloaded and exceed the value of its type power (the type motor is normally designed to operate without external cooling), the sizing of the protection is in this case carried out according to the higher value of the electrical parameters on the fan label. This applies not only to the motor power but also to the temperature parameters (type motors with an ambient operating temperature of up to 40 °C operated in fans in an air stream with less than the labelled power can be operated in this way in some cases up to 70 °C, for example).
Important notice 1
For fans for ordinary environments, the electrical values indicated on the fan label are always decisive for the sizing of the protection. The values on the fan nameplate always take precedence over the data given in the various catalogues. The data in the catalogues are indicative and may not be up-to-date due to the constant innovation of the products, of which there are over 7000.
Important Notice 2
The situation is different for non-explosion fans. For Exe fans, the values on the motor label are binding for the sizing of the protection. These are in particular the tripping time te and the Ik/In value. The tripping time is indicated on the motor label, must not be exceeded and is related to the maximum permissible motor temperature. The Ik/In ratio value indicates the multiple of the fan starting current and the rated current. The fan current protection must be set according to both of these values.
Catalogue values
The data in the catalogues are indicative and may not be up-to-date due to continuous product innovation, especially when using motor series from different manufacturers, some values may differ, but this does not affect the functionality of the fan.
The values on the motor or fan label for fans for normal environments always take precedence over the values given in the various catalogues. The data in the catalogues are indicative and may not be up-to-date due to continuous product innovation). The values on the Exe motor label of an Exe fan always take precedence over those in the various catalogues. The data in the catalogues are indicative and may not be up-to-date due to continuous product innovation)