How should the allowable fluctuations of constant temperature and humidity units be written into the technical requirements?

The allowable fluctuations of the constant temperature and humidity unit should indicate the control object, set value, allowable range, working conditions, measurement location and evaluation time. Just writing 'temperature ± a certain value, humidity ± a certain value' can easily confuse control deviation, spatial uniformity and instrument error, and cannot form a consistent acceptance conclusion.

Split a tolerance into six elements

First explain whether it is air supply or room, then give the set points and upper and lower limits, explain the stable operating conditions, point layout method and recording interval. Humidity also needs to be paired with corresponding temperature. For door opening or load switching, if the recovery time needs to be evaluated, the trigger conditions and the criteria for returning to the target range should be written separately to avoid confusion with steady-state fluctuations.

The range definition should write the set value, upper and lower limits and applicable control objects; the test definition should write the instrument capability, measuring points, sampling interval and evaluation period; the dynamic definition should write the disturbance scenario, allowable process and recovery judgment conditions. The three categories of definitions correspond to different evaluation methods, and you cannot just give a '±' value. What is the difference between air supply accuracy of air conditioning box and room control accuracy? Please refer toWhat is the difference between air supply accuracy of air conditioning box and room control accuracy?。

First, let’s make it clear whether the air supply or the room is being controlled.

The allowable fluctuation of air supply describes the deviation of the air outlet state of the unit relative to the set value. The measuring point is usually at the air supply duct or the outlet of the unit. The room allowed fluctuation describes the deviation of temperature and humidity in the service area relative to the set value, and the measuring points are usually arranged in representative areas. The responsible entities and influencing factors of the two are different, and the technical requirements should be stated separately.

What control objectives should be clarified when selecting a constant temperature and humidity air conditioning box? Please refer toWhat control objectives should be clarified when selecting a constant temperature and humidity air conditioning box? . Room accuracy is also affected by airflow distribution, local loads and door openings, please refer toWhat is the difference between air supply accuracy of air conditioning box and room control accuracy?。

Humidity tolerance must be paired with temperature

Relative humidity changes with temperature. Simply writing 'humidity ±5%' without specifying the corresponding temperature range may cause ambiguity during acceptance. The humidity tolerance should indicate whether it is relative humidity, moisture content or dew point, as well as the corresponding temperature conditions and measuring points. If the process is concerned with moisture content, moisture content or dew point is more stable than relative humidity.

Why do you need to consider the temperature when selecting an air-conditioning box based on relative humidity? Please refer toWhy does air conditioning box selection depend on relative humidity and temperature? . The role of supply air dew point in selection can be referred toWhat role does the supply air dew point play in the selection of fresh air air conditioning boxes?。

Measuring instruments and measuring points must be traceable

The evaluation of allowed fluctuations depends on the measuring instrument. The technical requirements should describe the instrument type, measuring range, allowable error, calibration status and sampling interval. The location of the measuring point should be away from local hot and cold airflow and the influence of the wall. If the instrument accuracy is close to the tolerance of the measured instrument, the measurement uncertainty may mask the true deviation.

How to determine the installation and calibration requirements for air conditioning box temperature and humidity sensors, please refer toHow to determine the installation and calibration requirements for air conditioning box temperature and humidity sensors? . How to position the supply air temperature sensor to avoid local airflow, please refer toHow should the air supply temperature sensor of the air conditioning box avoid the influence of local airflow?。

Steady-state fluctuation and dynamic recovery should be written separately

Steady-state fluctuation refers to the small changes in parameters around the set value of the system under stable operating conditions. Dynamic recovery refers to the process and time during which parameters deviate and return to the allowable range after sudden changes in load, door opening, or mode switching. The two evaluation methods are different, and the technical requirements should separately specify test scenarios, allowable deviations and recovery criteria.

Circulating air handling units should be selected based on which indoor loads, please refer toWhat indoor loads should the circulating air handling unit be selected based on? . For the influence of control mode and load changes, please refer toWhich sensors and valve status should be checked when the air outlet from the air conditioning box is too cold?。

How to prevent both parties from interpreting each other’s understanding in technical negotiations

It is required that a complete example be written in the technical confirmation form, and the equipment side and system side respectively confirm the part they can bear. The more stringent the value, the more load, energy and measurement uncertainty need to be checked. The slogan 'high precision' without clear test boundaries cannot replace enforceable acceptance terms.

What applicable standards should be listed in the technical documents for purchasing air-conditioning boxes? Please refer toWhat applicable standards should be listed in the technical documents for purchasing air-conditioning boxes? . Equipment and verification boundaries for pharmaceutical projects, please refer toHow to define the boundaries of equipment and verification work in the air-conditioning box of pharmaceutical clean workshop?。

Aili industrial supporting equipment

When confirming the control configuration with Aili Industrial, you can submit complete tolerances and measurement conditions first, so that sensors, actuators and control strategies can be checked against the same goal. Aili's industrial manufacturing end covers independent R&D and production of motors and fans, control systems, sheet metal, air filters and complete machine assembly. Coils, humidification sections, sensors and control logic can be matched in the same package; non-standard tolerance requirements can be adjusted according to project measurement points and verification plans.

Product form can be viewedAir handling unit andFan box page; clean air supply package can be combinedFFU fan filter unit andEFU equipment end fan filter unit verification; terminal particle filtration can be combinedHEPA/ULPA filter confirmation; when it comes to gaseous pollution control, you can communicate separatelyChemical filter solutions. Specific tolerance terms, control boundaries and delivery scope still need to be confirmed based on project technical requirements and on-site working conditions. The actual effect is subject to on-site debugging and performance test results.

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

Related questions and answers

Is it enough to just write 'temperature ±1℃, humidity ±5%'?
not enough. It is also necessary to explain the control objects, set values, working conditions, measuring points, instruments and evaluation periods, otherwise ambiguity will easily arise during acceptance.

Does the relative humidity tolerance need to be matched with temperature conditions?
need. Relative humidity changes with temperature. The corresponding temperature range and measuring point should be stated, or the moisture content and dew point should be expressed instead.

Can Aili Industrial help write tolerance clauses?
The tolerance writing method can be checked based on the control objectives, measuring point locations and instrument capabilities. Specific terms need to be confirmed based on project requirements and product information.

Related articles

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

2. What control objectives should be clarified when selecting a constant temperature and humidity air conditioning box?

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

4. What applicable standards should be listed in the technical documents for purchasing air-conditioning boxes?

Key points for selection and acceptance inspection