Laboratory ventilation control system can adopt different control modes according to different situations, such as single ventilator constant air volume ventilation control system, multiple ventilator constant air volume ventilation control system, multiple ventilator variable frequency ventilation control system, multiple ventilator variable air volume ventilation control system.
Fixed air volume ventilation control system of single ventilator.
1. Principle:
The constant air volume ventilation control system of single ventilation equipment means that the exhaust air of each detoxification cabinet is effectively discharged into the atmosphere by an independent set of ventilation ducts and a fan. The switch of the fan and the start of the exhaust system are installed on the detoxification cabinet or ventilation equipment. The control valve above the detoxification cabinet is an electric valve or a manual valve.
2. Advantages:
1) Simple operation, the switch of the system does not affect other roommate equipment, only refers to the required ventilation equipment.
2) Prevent the series connection of ventilation system and the return of exhaust gas.
3) Easy to control the air flow.
4) The operating cost of the system is low.
3. Disadvantages:
1) The cost of the system is high in the early stage.
2) The installation is complex and the installation space is in great demand.
3) Long-term maintenance is expensive.
4. Applicable conditions:

Special functional laboratories such as P2 laboratory, P3 laboratory, aseptic room, radioactive laboratory, PCR laboratory, animal laboratory, DNA laboratory, etc.

2. Fixed air volume ventilation control system for multiple ventilation cabinets.
1. Principle: Fixed air volume ventilation control system of multi-ventilation equipment means that multi-ventilation cabinet or ventilation equipment is discharged by a fan in series through a group of pipes, and the control valve above the exhaust cabinet is an electric valve. There are two control modes in this mode:
1) Fixed-point control. All ventilation equipment is started or closed at the same time with only one switch.
2) Multi-point control. Install switches on many ventilation equipments or laboratories. As long as one of the switches is still in the start-up stage, the fan will still be in operation. Only when all the switches are disconnected will the fan stop. The whole ventilation system will stop shutting down.
2. Advantages:
A. Reduce the use of materials, reduce early investment.
B. Simplify the installation of ventilation system and reduce the need for installation space.
C. Relative reduction in maintenance costs.
D. Multi-point control can achieve the concept of "people-oriented" laboratory, which is convenient for operators to switch the required equipment according to the situation.
3. Disadvantages:
A. It belongs to the constant air volume exhaust. It needs 100% exhaust. The larger the system, the more wasteful it will be.
A lot of energy.
B. Pipeline operation, noise, air volume is not easy to balance, leading to exhaust air volume
The problem of foot.
C. Exhaust air volume can not be controlled freely and discharged according to actual demand.
4. Applicable conditions:
Physical and chemical laboratories, preparation rooms and dispensing rooms with low requirements are not very good in performance and are not recommended for use.
3. Frequency conversion ventilation control system of several ventilation cabinets.
In large-scale ventilation system, if a single detoxification cabinet is used with independent constant air volume exhaust mode, it will lead to too many exhaust ducts, insufficient size of pipe wells or all the exterior walls of pipelines are not beautiful, and a large one-time investment. If multiple ventilation equipments are used with a constant air volume ventilation system, although the one-time investment is reduced, the operation is not energy-saving. When some ventilation equipments are not used, the exhaust volume of other ventilation equipments will increase or even exceed the normal air volume, which will affect the operation of the experiment, and the operation cost of the fan is also very high. Certain disadvantages.
In order to reduce one-time investment and save operating costs, frequency conversion ventilation system came into being. Frequency conversion ventilation system means that many ventilation equipments share one fan and adopt frequency conversion control technology to automatically adjust the operation of the fan according to the usage of the ventilation equipment, so as to achieve the purpose of energy saving.
1. Principle:
The principle is: adding air duct pressure sensor on the main pipe of ventilation pipeline, setting up frequency conversion cabinet, installing frequency conversion controller in the frequency conversion cabinet, and controlling the air volume of the system by setting up a pressure value of air duct initially. When some ventilation equipment is not used, the pressure of the ventilation main pipe changes. When the pressure sensor detects the pressure change, it converts the pressure change into a voltage signal of 0-10V, which is transmitted to the frequency conversion control cabinet. The frequency conversion control cabinet converts this signal into a current value to control the frequency converter and reduce the frequency converter. The working frequency, because of the frequency change of the frequency converter, produces the current change to control the speed of the fan, in order to achieve the purpose of reducing the exhaust of the fan.
Frequency conversion speed regulation is an advanced and mature technology, which converts frequency-fixed AC into DC through rectifier, inverter and control circuit, and then converts DC into AC with different frequencies, so as to achieve speed control of AC asynchronous motor.
The control valve above the detoxification cabinet is an electronic air regulating valve, which is a new type of micro-computer air valve.
2. Advantages of variable frequency speed regulation:
1) The electronic air conditioning control panel can be directly installed in the upper column or lower seat of the detoxification cabinet, which is easy to operate and intuitive.
2) The angle of the air valve can be adjusted arbitrarily from O to 90. The operator can set the angle of the air valve arbitrarily through the touch button of the control panel of the air valve. The air valve will automatically save the setting value.
3) The electronic air-conditioning valve can switch the air valve and the fan, and can switch the fan on-line with multiple air valves. It can also be used as a controller in the frequency conversion control system to output signals to the PLC and the frequency converter to control the output of the frequency converter, so as to control the air volume and keep the air volume of the detoxification cabinet constant.
4) Electronic air-conditioning valve can replace lighting and system switch at the same time, reduce all kinds of electrical equipment on the detoxification cabinet, and improve the safety protection of operators.
5) The electronic air-conditioning valve can reset to 0 automatically when it is turned off, so it has the function of check valve at the same time. The exhaust gas from other working detoxification cabinets will not flow back into the detoxification cabinet.
3. Advantages of PLC frequency conversion control:
1) Efficiency: Frequency conversion speed regulation is adopted to directly regulate the air flow, so as to reduce the reactive power and improve the working efficiency of the system.
2) Energy-saving: After frequency conversion speed regulation, the fan generally operates at 30-45Hz, saving energy up to 25-70%. The lower the frequency, the higher the power-saving rate.
3) Extend the life of fan system: realize the real frequency conversion soft start, reduce the impact of motor start on the power grid and the harm to the motor itself, and improve the life of motor and the life of the system.
4) Improve the operation quality of fans: In the past, fans always run at full speed of 50Hz power frequency, and the operation quality of fans is very low; but after adopting frequency conversion speed regulation, the operation quality of fans is greatly improved by adjusting the frequency in time with the amount of air to adjust the speed.
4. Disadvantages:
Frequency conversion system is connected by many ventilation equipments. The ventilation system requires the height of the room and the size of the pipe well. Only the room with high height can be used as frequency conversion system. Because the air duct size of the frequency conversion system is large.
5. Applicable Conditions: There are many ventilating equipments in the same room or multiple rooms at the same time, so frequency conversion system should be adopted. It can save energy effectively.
IV. Frequency Conversion + Variable Air Volume Ventilation Control System.
In large-scale ventilation system, when many cabinets are connected together and controlled by frequency conversion system, the air volume of the main air duct can only be controlled. Only when the air pressure of the main air duct changes, the fan can be adjusted accordingly, and the face wind speed of the ventilation equipment can not be adjusted at all. In the case of ventilation equipment requiring variable air volume control or constant surface wind speed, the use of frequency conversion system can not effectively control the end of ventilation equipment.
In order to meet the requirement of variable air volume at the end of ventilation equipment and the requirement of constant surface wind speed, and realize further energy saving, a variable frequency and variable air volume ventilation control system has been developed. The variable frequency and safe air volume ventilation control system includes a wind speed sensor, an infrared detector, a variable air volume control scale, an automatic controller panel and an operation terminal.
1. Principle:
After adding the terminal control system, a wind speed sensor and an infrared detector are arranged on the side of the ventilation cabinet. The measured air speed on the top of the exhaust cabinet is compared with the reasonable inlet air speed value set in advance in the automatic controller. The variable air volume control valve on the air duct of the exhaust cabinet is controlled and the exhaust gas is adjusted. The exhaust volume of the poison cabinet ensures that the wind speed at the entrance of the door is constant, and that the pollutants in the cabinet are evenly mixed, so that they can be completely eliminated. The purpose of the infrared detector is to detect whether there is anyone in front of the detoxification cabinet. When someone operates, the exhaust air increases automatically, and when people leave, the exhaust air decreases automatically. When someone is present, the face wind speed of the detoxification cabinet is set at 0.5m/s, and that of the detoxification cabinet is set at 0.3m/s when no one is operating.
The main air duct is also equipped with a frequency conversion control system. The main air duct terminal is equipped with a wind pressure sensor, which compares the measured variable air volume and the set wind speed value in the automatic controller. The output of the frequency converter is controlled by the calculation and allocation of the control box, so as to adjust the speed of the motor on the fan, so as to achieve the purpose of regulating the air volume. The control valve above the poison exhaust cabinet is the variable air volume regulating valve. (VAV valve).
2. Advantages:
1) Efficiency: Frequency conversion speed regulation is adopted to directly regulate the air flow, so as to reduce the reactive power and improve the working efficiency of the system.
2) More energy-saving: adding sensors to control the frequency converter at the end of the variable air volume is much more accurate than using the pressure sensor of the official head of the variable-frequency system alone to control the frequency converter. After the variable-frequency speed regulation, the fan generally operates at 30-45 Hz, saving energy up to 50-70%. The lower the frequency, the more energy-saving. Generally, the variable-weight control system is adopted. The cost can be recovered in about one year, and the operation cost can be saved by 80% in 10 years.
3) Extend the life of fan system: realize the real frequency conversion soft start, reduce the impact of motor start on the power grid and the harm to the motor itself, and improve the life of motor and the life of the system.
4) Improve the operation quality of fans: In the past, fans always run at full speed of 50Hz power frequency, and the operation quality of fans is very low; but after adopting frequency conversion speed regulation, the operation quality of fans is greatly improved by adjusting the frequency in time with the amount of air to adjust the speed.
3. Disadvantages:
Frequency conversion system is connected by many ventilation equipments. The ventilation system requires the height of the room and the size of the pipe well. Only rooms with enough height can be used as frequency conversion + variable air volume system.
4. Applicable Conditions: There are many ventilation equipments in the same room or in many rooms at the same time. It is advisable to use frequency conversion + variable air volume system, which has the best control effect and the most energy saving.