The selection of centrifugal fan needs to consider many factors, one of which is to balance the pre-installation cost and post-operation cost. The installation cost here includes centrifugal fan cost, motor cost, fan installation size and so on. However, there are many factors that are not completely clear in the early design stage, so collect as much information as possible, even if it may be inaccurate. At the design stage, staff usually add a lot of safety factors to the selection.
But the safety factor of some systems is too big to be necessary. For example, the actual operating pressure of centrifugal fan is only 50% of the expected pressure. As a result, the fan runs at a very efficient point, and even the operating point deviates from the selection point too far, resulting in motor overload. Although it can change the speed of the fan to solve the problem of motor overload. But it also loses a lot of air volume and reduces the production capacity of the system.
In this case, the simple solution is to choose high-power motor, but it will increase the installation cost and later operation cost. Instead of only considering increasing the pressure safety margin in the design, it is better to combine the safety margin with the type selection of the fan to increase the pressure range from the use pressure to the highest point of the fan curve, so that the operating pressure has a larger margin.
If the initial system design reserve 20% safety factor is considered to be ideal, then the selection of centrifugal fan should select the operating point pressure of fan at least 15% lower than the maximum pressure, and reserve 10% safety factor at the same time. This ensures that the selected fan will be closer to the required operating point during operation.
However, electricity is not the only cost loss. Reducing the failure rate of centrifugal fans, reducing the parking time and saving the cost of repairing manpower and material resources play a vital role in reducing costs. Only by choosing high quality centrifugal fans, the cost saved by reducing the repairing rate is equal to or even higher than that saved by energy-saving fans.