How to check the original motor load when rebuilding a chemical filter?

In the renovation project, after adding a chemical filtration section, the resistance that the fan has to overcome becomes larger. Whether the original motor can continue to be used at this time is a question that many people are concerned about.

Direct answer: You cannot simply say 'can' or 'can't'. It needs to be verified based on the fan performance, control method and actual operation measurements. After adding resistance, the air volume may decrease and the motor load may change. The direction of change depends on the fan type, control method and system operating point. Judging based solely on experience is prone to deviations.

Get actual operating data

The first step to check the motor load is to measure the true state of the original system.

Motor nameplate. Record the motor model, rated power, rated current, rated voltage, frequency, speed and protection level. These are the benchmarks for judging what is allowed.

Fan parameters. Record the fan model, rated air volume, rated static pressure and speed range. If there is a fan performance curve, use it directly; if not, it can be calculated based on actual measured data. For specific curve applications, please refer to Discussion of how much the added resistance of the chemical filter will increase the fan's electricity consumption .

Current operating point. Measure the actual air volume, pressure difference in each section, fan gear or frequency before modification. At the same time, record the actual operating current or input power of the motor. The measurement methods of three-phase motors and single-phase motors are different and should be measured in corresponding ways.

control method. Record whether the fan is a fixed speed, variable frequency or EC motor. Under different control methods, the impact of new resistance is different. For specific differences, please refer to Discussion on whether adding a chemical filter to an old air conditioning system requires replacing the fan .

Calculate working points under new resistance

With the data, the working points after the transformation can be calculated.

How much new resistance is there? Obtain the initial resistance and final resistance data at the target air volume from the supplier of the chemical filtration section. Pay attention to the final resistance condition, because the resistance of the filter material will increase in the later stages of operation. For specific life assessment, please refer to Discussion of how long chemical filters last .

The total resistance of the system changes. Add the resistance of the chemical filtration section to the total resistance of the original system. The total system resistance includes pre-filtration, surface cooler, heater, air duct, valve and terminal filter. For specific calculations, please refer to Discussion of what conditions should be evaluated first before adding a chemical filter to an existing clean room .

Where is the new work point? Put the new system resistance curve and the original fan curve together and find the intersection. The air volume and static pressure corresponding to this intersection point are the working points after the transformation.

How much does the air volume change? If the air volume at the new working point is still within the design range, it means that the original fan still has margin. If the air volume drops significantly, the speed or fan configuration may need to be adjusted.

Check the allowable range of the motor

After the working point calculation is completed, the allowable range of the motor itself must be checked.

Rated power and current. After adding resistance, if the fan speed remains unchanged and the air volume decreases, the motor load will usually not exceed the original state. However, if the rotation speed is increased to restore the air volume, the motor load may increase. For specific verification methods, please refer to Discussion on how to check the original motor load when rebuilding a chemical filter .

Speed ​​range. What is the allowable speed range of fans and motors? How far is the current operating gear from the upper limit? If it is already close to the upper limit, continuing to increase the speed may exceed the allowable range.

Temperature rise and insulation. When the motor runs close to the rated load for a long time, the temperature rise will increase. It is necessary to confirm whether the insulation level and cooling conditions of the motor are met. For specific inspections, please refer to Discussion on how to check the original motor load when rebuilding a chemical filter .

Control protection. Can the overload protection and overcurrent protection setting values ​​of the inverter or controller cover the new operating status? Protection parameters may need to be re-tuned.

On-site measurement and adjustment

The calculation is only a prediction, and it needs to be confirmed by actual measurement after the transformation is completed.

Measure current or power. Measure the actual operating current or input power of the motor under stable operating conditions, and compare it with the pre-transformation and calculated values. For specific measurement methods, please refer to Discussion on how to check the original motor load when rebuilding a chemical filter .

Measure air volume. Confirm that the actual air volume meets the design requirements. If the air volume is insufficient, first check whether it is a problem with the filter section resistance, the fan operating point or the air duct. For specific air volume balance, please refer to whether chemical filtration modification requires re-doing the air volume balance . Discuss

Check for noise and vibration. As the rotational speed increases, the noise and vibration may change. If there are noise requirements in the vicinity of the air conditioning system, or the equipment is sensitive to vibration, the impact will need to be assessed.

Record new baseline. The current, power, air volume, pressure difference and operating gear after the modification should be recorded and archived as a basis for subsequent maintenance. Please refer to the specific inspection records Discussion of what items should be checked during daily inspection of chemical filters .

Compare overall renovation plans

If calculation or actual measurement finds that the original motor has insufficient margin, there is more than one way to deal with it: replacing the motor.

Increase filter area. Choose a chemical filtration section with a larger effective area to achieve lower resistance under the same air volume. This method does not require replacing the motor, but you need to confirm whether the installation space allows it. Please refer to the specific thickness restriction plan. Discussion of how to determine configuration when chemical filter thickness is limited .

Optimize air ducts. Check existing air ducts to see if there are spaces where resistance can be reduced, such as cleaning out dust accumulation, reducing elbows, or adjusting valves. Such changes often do not require replacement parts.

Adjust the fan. If the first two methods are not satisfactory, consider replacing the fan or motor. When changing models, pay attention to the working point, motor power, control method and installation interface of the new fan, and make sure they match the original system. For specific decisions, please refer to Discussion on whether adding a chemical filter to an old air conditioning system requires replacing the fan .

Reevaluate goals. If system conditions dictate that air volume cannot be restored, you can evaluate whether the target area or air volume requirements can be adjusted. This needs to be confirmed with the craftsman.

Project judgment example

An old air conditioning system plans to add a chemical filtration section. Before the transformation, the operating current of the original motor was measured to be 70% of the rated value, and there was still room for the fan gear.

Calculations show that the new initial resistance is about 70 Pa, and the final resistance is about 140 Pa. Under the initial resistance condition, the original fan can be increased by one gear to maintain the original air volume, and the motor current is expected to rise to 78% of the rated value. Under the final resistance condition, the current is expected to rise to 85% of the rated value, which is still within the allowable range. After the transformation, the actual measurement showed that the current was close to the calculated value, the air volume met the requirements, and the original motor was not replaced.

Another project calculation found that the original motor was already running close to the rated load. If the speed is increased after adding a filter section, the current will exceed the rated value. After evaluation, a chemical filter section with a larger effective area was selected to reduce resistance. At the same time, the air valve was slightly adjusted, and the air volume requirements were finally met without replacing the motor.

These two cases illustrate: Checking the motor load must combine actual measured data, resistance calculation and speed regulation boundaries, and cannot just look at the rated power. involving When selecting a chemical filter product series , it is recommended to provide the motor parameters, operating data and new resistance to the supplier for verification.

Key points for selection and acceptance inspection

About Aili Industrial’s transformation and motor matching

Aili Industrial has independent manufacturing capabilities in filters, motors, fans, control systems and sheet metal processing, and can provide chemical filter product series and supporting air supply equipment. For renovation projects involving motor load verification, the original motor parameters, fan performance, system resistance and target air volume can be combined to assist in checking the chemical filtration section configuration and operation plan.

Related products:Chemical filter product series、MAU box chemical filter、FFU comes with chemical filter . Providing motor parameters, operating data and modification requirements when enquiring, will help confirm the appropriate solution. The specific selection is subject to the technical documents and test results confirmed by the project.