What mainly determines the energy consumption of fan box operation? Distinguish between power and running time
The annual power consumption of the fan box is equal to the sum of the input power of the whole machine multiplied by the corresponding operating hours under each operating condition. The input power of the whole machine is affected by the air volume, external static pressure, fan efficiency, motor drive efficiency and control method. The rated power of the motor is only the capacity boundary, not the fixed power consumption per hour. Treating the rated power as power consumption, or simply multiplying the power of one working condition by the number of hours throughout the year, will lead to conclusions that deviate from reality.
The same equipment has different power under different working conditions
The overall input power of the fan box changes with the operating point. The input power will change depending on the air volume, external static pressure, rotation speed, valve opening, and filter status. The motor may be close to full load under design conditions, but may only have 30% to 50% of the rated power during night duty or partial load. If more than half of the annual operating time is in a low-load state, using full load power to estimate the annual power consumption will result in a significantly higher estimate.
On the other hand, if the calculation is only based on low load power, the electricity consumption during peak production hours will be missed. The correct approach is to break the annual operation into several typical working conditions, record the input power and operating hours of the whole machine in each working condition, and then multiply the items one by one and add them up.
The input power of the whole machine should be measured on site or on the test bench, rather than replaced by the rated power of the motor. The rated power of the motor is used to define the capacity of the motor. The input power of the whole machine is the actual power consumption of the fan box under specific working conditions, including the comprehensive result of motor loss, driver loss and fan aerodynamic efficiency. The two are not the same number.
The impact of system resistance on energy consumption is easily underestimated
Clogged filters, pipes that are too long or too narrow, local sharp bends and air leaks will all cause the fan box to be in unsatisfactory operating conditions for a long time. Energy consumption problems are not necessarily caused by the motor alone. After the filter accumulates dust, the resistance rises, and the fan operating point moves to the direction of small air volume. If the terminal air volume is insufficient, the operator may increase the speed to compensate, and the input power of the whole machine will increase accordingly.
Air duct leaks are equally easy to overlook. Air leakage will cause the fan to supply more air, but not enough air volume at the end. Measure the air volume at the fan outlet and the main branch air volume. If there is a significant difference between the two, it indicates serious air leakage. Repairing the air duct first and then evaluating whether the power equipment needs adjustment is often more effective than directly replacing the high-efficiency motor.
Increased system resistance also changes the fan's operating point. The fan performance curve remains unchanged, but the system resistance curve becomes steeper and the intersection moves toward the direction of smaller air volume. At this time, even if the motor is still running in the high-efficiency zone, the input power of the whole machine may increase due to the deviation of the operating point. Dealing with system losses first and then evaluating the power plan is the correct sequence for energy consumption analysis.
Maintenance status directly affects annual power consumption
Dust accumulation on the filter, dust on the impeller, loose belts or worn bearings will all affect the actual energy consumption of the fan box. If the annual power consumption estimate only uses short-term test values under new filters and clean air ducts, it is often not enough to represent the entire operation process. Maintenance planning and energy consumption calculations need to correspond to each other.
For systems with filter sections, it is recommended to record the initial resistance of the filter, the pressure difference during operation and the final resistance when replacing. This data can help determine the average operating point throughout the year, rather than just using an ideal power number. System end configurationWhen using HEPA/ULPA high-efficiency filters , the initial resistance of the filter and the resistance at the end of use should be included in the calculation of the working point. When the process requirements are higher, it can be evaluatedDoes the ULPA ultra-high efficiency filter meet the requirements?
Calculate annual electricity consumption by time period
Multiply the input power in working, duty and peak modes by the annual operating hours, and then sum them up to get the estimated annual power consumption. The electricity price only affects the amount of the fee and does not change the power consumption of the device itself. If the terminal air volume is different before and after the transformation, the working conditions should be corrected first, and then the energy saving benefits and payback period can be discussed.
From the fan law, the air volume is proportional to the rotational speed, and the shaft power is proportional to the cube of the rotational speed. The rotation speed is reduced by 20%, the air volume is reduced by approximately 20%, and the shaft power is reduced to approximately 51% of the rated value. This is the fundamental reason why speed regulation can save energy. However, the actual energy saving depends on the load curve, system resistance characteristics and speed regulation strategy. If the system operates at full load for a long time, the benefits brought by speed regulation will be limited; if there are obvious on-duty or partial load periods, the value of the speed regulation solution will be reflected.
The control method determines the power in each period
The fan box running at a fixed speed can only rely on valve throttling to adjust the air volume. During low load periods, the fan is still running at high speed, and the excess air volume is consumed by the valve. The speed-regulated fan box can allow the speed to follow the actual demand and reduce the input power during low load periods. Under the two control methods, there may be significant differences in electricity consumption throughout the year, but only if the system does have adjustable load changes.
For systems shared by multiple devices, attention should also be paid to branch balance. If one branch is closed while other branches remain open, the fan operating point will change. Controlling the rotation speed based on only one sensor may result in insufficient air volume in the remote area. The control strategy should ensure that the most unfavorable end still meets the minimum demand under each typical combination state.
Looking at energy consumption optimization space from the perspective of whole machine matching
The space for optimizing energy consumption often lies not in individual components, but in whether the matching of the entire machine is reasonable. The impeller and motor torque characteristics do not match, the driver parameters do not correspond to the fan curve, and the air path loss inside the box is too large, which will make the input power of the whole machine higher than necessary. Aili Industry has independent supporting capabilities in fans, motors, controls and sheet metal structures. It can calibrate the impeller, motor, driver and box at the same working point, so that the speed adjustment range can be determined around the actual operating conditions of the project, rather than simply applying standard configurations. This kind of internal collaboration from the power end to the complete machine structure can reduce common matching deviations in outsourced assembly solutions, allowing energy consumption calculations to be based on complete machine test data, rather than a simple superposition of parts sample data.
If the system is compatible withFor HEPA/ULPA high-efficiency filters , pressure difference changes should be included in the operation and maintenance plan. Clean room ceiling air supply is comparableFFU fan filter unit ; centralized management of multiple devices can be matchedThe FFU computer group control system realizes zone speed regulation and status monitoring. Protection of single process equipment can be consideredEquipment-side fan filter unit (EFU) . The final filtered air supply at the end of the air duct can beHigh-efficiency air supply outlet (HEPA BOX) . The division of labor between these equipment and the fan box should be clearly stated on the system flow chart.
Specific structure and configuration options can be found inIt is confirmed in the fan box product catalog that non-standard projects should provide equipment or machine room drawings, and then finalize them based on the determined working points and on-site interfaces.
