Division 3.1 Where the fan is supplied as a ‘final assembly’, measure the gas power and the electric input power of the fan at its optimum energy efficiency point:

where the fan does not include a variable speed drive, calculate the overall efficiency using the following equation:

η_e = P_u(s) / P_e

where:

• η_e is the overall efficiency;

• P_u(s) is the fan gas power, determined according to point 3.3, of the fan when it is operating at its optimal energy efficiency point;

• P_e is the power measured at the mains input terminals to the motor of the fan when the fan is operating at its optimal energy efficiency point;

where the fan includes a variable speed drive, calculate the overall efficiency using the following equation:

η_e = (P_u(s) / P_ed) · C_c

where:

• η_e is the overall efficiency;

• P_u(s) is the fan gas power, determined according to point 3.3, of the fan when it is operating at its optimal energy efficiency point;

• P_ed is the power measured at the mains input terminals to the variable speed drive of the fan when the fan is operating at its optimal energy efficiency point;

• C_c is a part load compensation factor as follows:

  • for a motor with a variable speed drive and P_ed ≥ 5 kW, then C_c = 1,04,

  • for a motor with a variable speed drive and P_ed < 5 kW, then C_c = – 0,03 ln(P_ed) + 1,088.