In the case of hydraulic installations, the nominal rating of the drive motor must be such as to ensure maximum output from the pump at maximum pressure in the installation (safety valve setting) having regard to the efficiency of the pump.

If the power can be measured only with the gearbox fitted to the engine the efficiency of the gearbox is taken into account;

If the power can be measured only when a gearbox is attached to the engine the efficiency of the gearbox must be taken into account;

If the power measurement can be carried out with an installed gearbox only, the efficiency of the gearbox is to be taken into account;