Optimizing paint booth performance through integrated climate and fan control
To make the most of the use of high-efficiency components, the paint booth must be equipped with an automatic control system for integrated management of all variables.
The use of advanced logic to optimize the operation of high-efficiency components – such as modulating fans, direct expansion systems, heat pumps, adiabatic humidifiers, evaporative coolers, heat exchangers and motorized dampers – allows for significant reductions in energy consumption without compromising the quality of the painting process.
The electronic control is the heart of the ventilation system serving the paint booth. It is the key to an effective and efficient system and one that fails to meet process demands. To ensure optimal control over time, the electronic control must be connected to appropriate sensors, which are used to activate and manage the various air handling unit (AHU) devices. Additional sensors and control devices are also required to detect and manage alarms and limit conditions.
What are the most important components of an AHU in painting processes?
Fan control
Fan control is essential to maintain the expected airflow operating conditions. Given the critical importance of this aspect, paint booths do not use simple ON/OFF fans, but rather modulating fans. The control modulates the speed during operation and manages all safety checks to be performed during startup, shutdown, and in the event of alarms.
The ON/OFF sequence, along with the corresponding timing, depends on the interaction with the other AHU devices. A typical example involves turning off the fan simultaneously with the electric heater or gas burner: in this situation, the fan must remain on even after the OFF command is given to eliminate residual heat, preventing component overheating and damage to the combustion chamber.
Fan speed variation is also used to compensate for changes in pressure drop, both inside and outside the AHU, thus maintaining a constant airflow. Additionally, in some paint booths, multiple flow points may be required for different process phases. To control fan speed, simply measure the air velocity in the duct or the differential pressure. For stable control, a PID (proportional integral derivative) algorithm is strongly recommended.
Example of inversely proportional control for pressure-based fans
A common solution to compensate for pressure drops is the use of radial fans with pressure measurement directly at the inlet nozzle: since the pressure drop at this point is calibrated, measuring the differential pressure allows the flow rate to be monitored and the fan speed to be adjusted, keeping it constant. Clogging of filters, at the same speed, causes a reduction in flow and, consequently, a pressure drop at the inlet nozzle, leading to an increase in fan speed.
Pressure measurement at the calibrated fan inlet nozzle
Large AHUs often use multiple supply and extract fans. For example, two fans in parallel are a useful solution to allow for shorter and wider AHUs in space-constrained situations. In this case, simply duplicate the control outputs, maintaining the same control probe but managing the flow or motor thermal overload alarms individually; an additional function could be to apply a delay between the two devices, preventing both motors from starting simultaneously.
The evolution of this concept led to the use of multiple radial fans (two, four or more) arranged side by side, forming what is called fan wall , with the aim of increasing redundancy and often reducing the size of the AHU. Controlling two fans or a fan wall is similar; however, when there are multiple devices, serial communication is recommended to reduce the number of outputs required and allow monitoring the status of each device individually.
Temperature and humidity control
Temperature and humidity control is essential to maintain optimal air conditions inside the paint booth and ensure maximum process quality. This is achieved by modulating control valves in heat exchangers, burners, humidifiers, and other components based on readings from sensors installed in the AHU inflation conduit.
Controlling the supply air directly is the ideal solution, as the high number of air changes ensures that the supply air temperature matches the temperature inside the cabin. This allows sensors to be positioned in the clean air stream before it is blown into the cabin, avoiding the need for expensive ATEX sensors inside the cabin or in the exhaust air, where they would be subject to high levels of contamination and maintenance.
Temperature and humidity control depends on outside air conditions, which can vary significantly depending on the time of year and the climate of the installation site. The most common function is heating, essential both during the painting and curing phases and in intermediate phases such as body preparation and drying. In many regions of the world, cooling is also necessary for good quality control of the process in general.
Furthermore, controlling relative humidity is essential and, depending on the technology used, it also influences temperature, making control more complex and even more important to keep all variables under control.
Below are some typical examples of integrated temperature and humidity control in adiabatic humidification and evaporative cooling systems.
Conclusion
The adoption of intelligent and integrated control systems is essential to ensure optimal performance and energy efficiency in ventilation and air treatment in paint booths. From precise fan modulation to stable temperature and humidity regulation, each component must be carefully coordinated to maintain process conditions and reduce energy consumption.
In the next blog post, we'll explore more advanced aspects of integrated control, focusing on adiabatic humidification, evaporative cooling, and heat recovery systems. These technologies play an essential role in managing environmental conditions sustainably and economically—don't miss the next article, where we'll delve deeper into their control logic and practical applications.
