Which sensors and valve status should be checked when the air outlet from the air conditioning box is too cold?

When the air outlet from the air conditioning box is too cold, you should first confirm the true temperature, current operating mode and set value, and then check the return air measuring point, cold water valve command and actual action, and whether dehumidification is in progress or reheating has failed. The low-temperature intermediate state during dehumidification operation should not be directly confused with the final air supply target.

Separate what the controller wants to do from what the device actually does

Check whether the temperature probe is in a local cold air flow or is installed in the wrong position, and then cross-check with an appropriate instrument. A valve command of zero does not necessarily mean that the waterway has been shut off. The valve position and possible leakage should be observed. If the system is reheating, verify its permissible conditions, heat source, and actual output rather than just looking at the screen icons.

The target and mode should write the air supply settings, dehumidification requirements and current priority control tasks; the temperature evidence should write the measuring point location, reading reliability and upstream and downstream status; the execution evidence should write the actual action of the cold water valve, reheat permission and heat source conditions. The three types of information correspond to different investigation directions, and you cannot just look at one outlet temperature. How to avoid the influence of local airflow on the air supply temperature sensor of air conditioning box, please refer toHow should the air supply temperature sensor of the air conditioning box avoid the influence of local airflow?。

First confirm whether the sensor readings are credible

Supply air temperature probes may give low readings if installed near local cold air flows, coil outlet jets, or walls. Readings can also be affected if the probe is not inserted deep enough, has a protective sleeve that is too long, or is positioned close to a cold surface. A calibrated portable instrument should be used to cross-measure at the same location or a representative section to confirm whether the control screen reading is consistent with the actual temperature.

For 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? . Whether the return air measurement point can represent the service area, please refer toCan the air conditioning box return air measurement points represent all service areas?。

The operating mode and setting values ​​must be checked first.

Dehumidification mode, preheating mode, reheating mode or duty mode may use different supply air temperature targets. If you are currently in dehumidification priority mode, the coil outlet air temperature may be lower than the regular air supply target. This is an intermediate state in the dehumidification process and is not necessarily a fault. The current operating mode, set values ​​and priority control tasks should be confirmed first.

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? . What problems do preheating, heating and reheating solve respectively? Please refer toWhat problems do air conditioning box preheating, heating and reheating solve respectively?。

The cold water valve command and actual action should be checked separately.

The control screen shows that the valve opening is zero, which does not mean that the valve is actually closed. A faulty valve actuator, detached connecting rod, stuck valve core, or impurities in the valve may allow cold water to continue to flow. The actual position of the valve, the action of the actuator and the pressure difference between the front and rear of the valve should be confirmed on site. If the valve is not closed tightly, the outlet air temperature may remain low.

Cold water parameters and flow conditions, please refer toWhat water parameters should be confirmed before connecting the air conditioning box to the cold water system? . For the relationship between coil water flow and design cooling capacity, please refer toHow does the water flow rate of the air conditioning box coil correspond to the designed cooling capacity?。

Reheat failure or failure to input will also cause the outlet air to be too cold.

If the system has a reheat section, but the reheat valve is not opened, the heat source temperature is insufficient, the reheat permission conditions are not met, or the control logic is not triggered, the dehumidified air may be sent directly into the room, causing the outlet air to be too cold. The reheat valve command, actual opening, heat source temperature and allowable conditions should be confirmed.

How to choose between hot water heating and electric heating, please refer toHow to choose between hot water heating and electric heating for air conditioning boxes? . For the position of the reheat section in the functional section, please refer toOn what basis should the sequence of functional sections of the air conditioning box be determined?。

Do not cover up equipment abnormalities by modifying setting values

If the valve is not tightly closed, the probe is offset, or the control logic is wrong, simply raising the set value may only temporarily alleviate the problem under certain working conditions. Instructions and measured trends should be recorded simultaneously, and control parameters should be adjusted after locating abnormalities. When valve disassembly or electrical inspection is involved, professionals should follow shutdown isolation procedures.

For control point table and mode definition, please refer toWhat point tables need to be provided before the air-conditioning box is connected to the building automation system? . For condition checks before starting the machine for the first time, please refer toWhat conditions need to be checked before the air conditioner is turned on for the first time?。

Aili industrial supporting equipment

Aili Industrial can check the equipment interface based on the control point table, temperature trend and valve status; it is especially useful to indicate whether it is in dehumidification mode when giving feedback. 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, reheat sections, sensors and control logic can be matched in the same package; non-standard configurations can be adjusted according to on-site measurement points and valve conditions.

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. The specific outlet air temperature performance, control logic and delivery scope still need to be verified based on the corresponding configuration data 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

If the air outlet temperature is too low, must the cold water valve be opened too large?
uncertain. It may also be caused by offset of sensor readings, dehumidification mode operation, reheat failure or loose valve closing, which should be checked one by one.

The control screen shows that the valve is closed. Is on-site inspection still required?
need. The screen displays instructions or feedback and does not represent the actual shutdown of the valve. The actuator and valve position should be confirmed on site.

Can Aili Industrial help troubleshoot excessive cooling of the air?
The control point table, temperature trend and valve status can be combined to help narrow the scope. Specific processing must be carried out by on-site professionals according to the equipment instructions.

Related articlen=linkage

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

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

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

4. What point tables need to be provided before the air-conditioning box is connected to the building automation system?

Key points for selection and acceptance inspection