How should the air supply temperature sensor of the air conditioning box avoid the influence of local airflow?

The air supply temperature sensor of the air conditioning box should be arranged at a position that can represent the target air state and avoid hot and cold stratification, coil local jets, heating radiation and wall effects. Installation on the supply side does not automatically guarantee that the reading represents the entire cross-section. The measurement point should be confirmed based on airflow mixing and actual control targets.

First explain what you want this measurement point to represent.

If the final air supply is controlled, the measuring point should correspond to the final treatment process; if it is used for coil protection or process monitoring, other dedicated positions may be needed, and one probe cannot take care of all tasks. Adjacent cold and heat sources, air leakage or heat conduction on the outer wall may also cause local readings to deviate from the average. The installation diagram should clearly indicate the location and insertion method.

Control objects should be distinguished between final air supply, process monitoring or component protection; airflow conditions should avoid stratification, local jets and areas of insufficient mixing; installation conditions should involve probe contact, wall influence and maintenance accessibility. What tasks the measuring point undertakes determines where it should be placed. This is more important than which probe to choose. If the same measuring point needs to participate in both control and acceptance, it is easy to swing between the two goals. You can refer toWhat is the difference between air supply accuracy of air conditioning box and room control accuracy?。

Why is the air supply side not equal to even mixing?

The airflow at the coil outlet often has localized jets and temperature stratification, and readings may be biased toward a certain airflow near the coil, heater, or box wall. The sharp bends and diameter changes at the fan outlet will also cause uneven cross-sections. If the probe is inserted into a corner where the airflow is concentrated, the temperature seen by the controller may be higher or lower than the cross-sectional average, and the adjustment results will deviate from the target. This problem is more obvious when the length of the mixing section is insufficient. Please refer toHow long is the air mixing distance required in the mixing section of the air conditioning box?。

Radiation and direct hot air blowing should also be considered near the heating section. If the outlet of the electric heating or hot water coil is close to the measuring point, the probe may feel the local high temperature first, while other areas of the cross section have not yet reached the target. The sensor installation location should allow for airflow development distance, or improve cross-sectional consistency through a flow equalizing structure.

How to verify if the location is appropriate

During debugging, you can compare the readings at different locations under representative working conditions to check whether they are still representative after variable air volume or mode switching. If there is a significant cross-sectional difference, the airflow should be improved or a suitable measurement method should be used according to the design instead of covering up the position problem through offset correction. Control parameters should also be adjusted after the measurement points are credible.

During verification, multi-point readings, fan speed and valve opening of the same section can be recorded at the same time to observe whether the differences change with the working conditions. If the difference only appears when the air volume is low or heating is turned on, it means that it is related to the airflow organization rather than the drift of the probe itself. For the overall ideas related to the installation and calibration requirements of temperature and humidity sensors, please refer toHow to determine the installation and calibration requirements for air conditioning box temperature and humidity sensors?。

Measuring points, probes and control systems should be checked together

Sensor selection, insertion depth, protective sleeves and wiring methods all affect readings. If the probe is too short, it may only measure the air near the wall. If the protective sleeve is too thick, the response may be slow. The sampling period and filter settings of the control system will also affect the displayed value. You cannot judge the quality of the measuring point just by using the numbers on the control screen. The purpose, measuring range and alarm conditions of the measuring points should be indicated in the electronic control point table to facilitate later maintenance.

After the location of the measuring point is determined, the maintenance space and replacement method must be checked. If the probe is installed in an inaccessible location, calibration and replacement will become difficult, and it may be easily ignored during long-term operation.

Aili industrial supporting equipment

Aili Industrial can check the measurement point reservation based on the process in the box and the electrical control point table. When submitting the request, please clarify the control or protection tasks undertaken by the probe. Aili Industrial can jointly check the fan, coil, filtration, sheet metal and control configurations, and mark the sensor location, insertion direction and maintenance space during the structural confirmation stage; the manufacturing end covers the independent research and development and production of motors and fans, control systems, sheet metal, air filters and complete machine assembly. The measuring points and box structure can be aligned in the same set of packages.

Product form can be viewedAir handling unit andFan box page; clean air supply package can be combinedFFU fan filter unit andCheck the fan filter unit at the EFU equipment end ; when it comes to gaseous pollution control, you can communicate separatelyChemical filter solutions. The specific control effect, applicable environment and delivery scope still need to be verified based on the corresponding configuration data and on-site working conditions. Actual results are subject to on-site leak detection and performance test results.

Submit project parameters:https://ailigy.com/contactus.html

Related questions and answers

Does the sensor installed on the supply side necessarily represent the supply air temperature?
uncertain. There may still be stratification and local jets on the air supply side. The measuring points should avoid these areas and confirm the representativeness based on the cross-sectional conditions.

The readings at the measuring points fluctuate greatly. Should I adjust the control parameters first?
Not recommended. You should first confirm the location of the measuring point, insertion depth and air flow status, and then adjust the control parameters after eliminating location problems.

Can Aili Industrial help determine the location of the sensor?
The location and installation method of the measuring points can be checked based on the process in the box, air flow organization and electrical control point table. The specific plan needs to be confirmed according to the project conditions.

Related articles

1. How to determine the installation and calibration requirements for air conditioning box temperature and humidity sensors?

2. What is the difference between air supply accuracy of air conditioning box and room control accuracy?

3. How long is the air mixing distance required in the mixing section of the air conditioning box?

4. Can the air conditioning box return air measurement points represent all service areas?

Key points for selection and acceptance inspection