Schematic overview
NOT FOR SALE YET - AC fans | liquid-coupled heat exchanger
Solution description
Modern temperature-based control system for air handling unit with liquid-coupled heat exchanger. This AHU features two fans with AC motors operating on a 3-phase 400 V power supply, with a maximum current of 9,5 A per motor. The unit incorporates a liquid-coupled heat exchanger equipped with a pump and a three-way valve. The solution ensures efficient heat transfer and precise temperature regulation, while also providing comprehensive frost protection for both air and water. The AHU includes a water heater complete with a pump and a responsive three-way valve and a water cooler with a modulating three-way valve and chiller. The solution offers complete command over the supply and exhaust dampers.
Additional specifications and description
This solution is designed to monitor and control an air handling unit that is shown in the schematic below:
Air handling unit consists of ten parts, which are: supply (1) and exhaust (10) air dampers; supply (2) and exhaust (7) air filters; liquid-coupled heat exchanger (3, 8); supply (4) and exhaust (9) fans; air heater (5) and air cooler (6).
Control logic description
This solution is intended to ensure that the AHU operates completely automatically. The operating mode is determined by sensor readings. The HVAC controller DRPUM includes predefined logic for various AHU parts.
To ensure optimal performance and to avoid potential damage to the air dampers, the supply and exhaust air dampers open 30 seconds before the supply and exhaust fans are activated. This is especially important for high-flow AHUs.
Two differential pressure transmitters, HPS-M-1K0-2, are used to assess the condition of the air filters. The measurements are sent to the DRPUM (master device). If the pressure drop on the filters exceeds the setpoint, the user will be notified that maintenance is required. The AHU, on the other hand, continues to operate regardless of how clogged the filter is.
The speed of the supply and exhaust fans can be controlled manually or automatically using frequency inverters FI-E-44095E2. Dual differential pressure transmitters, HPD-G-1K0, are also used to control fan operation. In case of mechanical failure (jamming, bearing breakdown), there will be no pressure drop and the master device will take the following actions: turn off frequency inverters, close air dampers, and notify the user of the error. The HPD-G-1K0 can be used to maintain a specific pressure difference in automatic mode.
Additionally, this AHU includes a liquid-coupled heat exchanger, the main parts of which are two coils. Moreover, safe and efficient operation of this system is impossible without a pump and three-way valve. The pump is responsible for medium transfer from one coil to another. The most common mediums for liquid-coupled heat exchangers are ethylene glycol and propylene glycol solutions. The primary purpose of a three-way valve is to protect the exhaust coil from freezing. To control its position, temperature sensor for fluid pipes, DTP-M, is installed near the entrance to the exhaust coil. Low temperature of the heat-transferring medium can afflict the exhaust coil in two ways. It can lead to the freezing of moisture that is contained in exhaust air, which will dramatically decrease heat transfer efficiency. In addition, low-temperature glycol has high viscosity. Such liquid can easily damage or destroy narrow coil tubes. To avoid these negative consequences, the position of the three-way valve is changed according to DTP-M readings in order to add warm medium into the exhaust coil. The recirculation system can be utilized both during cold and warm periods of the year if necessary.
The operation of the air heater is controlled by a duct temperature and humidity sensor, DSTHM-2. When the measured temperature exceeds the desired value, the 3-way valve begins to close, reducing the amount of hot water supplied to the air heater. Otherwise, if the measured temperature falls below the desired level, the 3-way valve gradually opens. To ensure a hydraulic regime, the pump runs at a constant speed at all times.
The air heater has two types of frost protection: air and water. A special relay – frost protection thermostat – is used to measure temperature and is installed directly after the heater. If the measured air temperature falls below 10°C (this setpoint is adjustable), the following sequence occurs:
Air handling unit consists of ten parts, which are: supply (1) and exhaust (10) air dampers; supply (2) and exhaust (7) air filters; liquid-coupled heat exchanger (3, 8); supply (4) and exhaust (9) fans; air heater (5) and air cooler (6).
Control logic description
This solution is intended to ensure that the AHU operates completely automatically. The operating mode is determined by sensor readings. The HVAC controller DRPUM includes predefined logic for various AHU parts.
To ensure optimal performance and to avoid potential damage to the air dampers, the supply and exhaust air dampers open 30 seconds before the supply and exhaust fans are activated. This is especially important for high-flow AHUs.
Two differential pressure transmitters, HPS-M-1K0-2, are used to assess the condition of the air filters. The measurements are sent to the DRPUM (master device). If the pressure drop on the filters exceeds the setpoint, the user will be notified that maintenance is required. The AHU, on the other hand, continues to operate regardless of how clogged the filter is.
The speed of the supply and exhaust fans can be controlled manually or automatically using frequency inverters FI-E-44095E2. Dual differential pressure transmitters, HPD-G-1K0, are also used to control fan operation. In case of mechanical failure (jamming, bearing breakdown), there will be no pressure drop and the master device will take the following actions: turn off frequency inverters, close air dampers, and notify the user of the error. The HPD-G-1K0 can be used to maintain a specific pressure difference in automatic mode.
Additionally, this AHU includes a liquid-coupled heat exchanger, the main parts of which are two coils. Moreover, safe and efficient operation of this system is impossible without a pump and three-way valve. The pump is responsible for medium transfer from one coil to another. The most common mediums for liquid-coupled heat exchangers are ethylene glycol and propylene glycol solutions. The primary purpose of a three-way valve is to protect the exhaust coil from freezing. To control its position, temperature sensor for fluid pipes, DTP-M, is installed near the entrance to the exhaust coil. Low temperature of the heat-transferring medium can afflict the exhaust coil in two ways. It can lead to the freezing of moisture that is contained in exhaust air, which will dramatically decrease heat transfer efficiency. In addition, low-temperature glycol has high viscosity. Such liquid can easily damage or destroy narrow coil tubes. To avoid these negative consequences, the position of the three-way valve is changed according to DTP-M readings in order to add warm medium into the exhaust coil. The recirculation system can be utilized both during cold and warm periods of the year if necessary.
The operation of the air heater is controlled by a duct temperature and humidity sensor, DSTHM-2. When the measured temperature exceeds the desired value, the 3-way valve begins to close, reducing the amount of hot water supplied to the air heater. Otherwise, if the measured temperature falls below the desired level, the 3-way valve gradually opens. To ensure a hydraulic regime, the pump runs at a constant speed at all times.
The air heater has two types of frost protection: air and water. A special relay – frost protection thermostat – is used to measure temperature and is installed directly after the heater. If the measured air temperature falls below 10°C (this setpoint is adjustable), the following sequence occurs:
- The supply and exhaust fans stop, then the air dampers close;
- The three-way valve fully opens;
- When the air temperature after the heater exceeds the setpoint, dampers and fans resume their normal operation.
Water frost protection is assured using a temperature sensor for fluid pipes DTP-M. It should be installed on the return water pipe at the air heater exit. If the measured water temperature falls below 25°C (the adjustable setpoint), the following scenario will occur:
- Both supply and exhaust fans stop, and the air dampers close;
- The 3-way valve fully opens;
- When the water temperature after the heater surpasses 25°C, dampers and fans resume normal operation.
The operation of the air cooler depends on measurements provided by the room temperature and humidity sensor RSTHM-2. If the actual temperature is higher than the desired value, the 3-way valve opens, allowing cold water to enter the air cooler. The position of the valve is determined by the temperature differential; the warmer the room, the wider the valve opens. Duct temperature sensors are not used to control the air cooler due to the fact that air can warm up while passing through the fan and ducts.
System configuration
This solution includes a network gateway DIG-M-2. It gives the user access to the online HVAC platform, SenteraWeb. An Ethernet cable or a Wi-Fi network can be used to establish the connection. It allows remote monitoring of data and adjustment of settings for the connected HVAC devices via the internet. Data logging is also supported.
System configuration
This solution includes a network gateway DIG-M-2. It gives the user access to the online HVAC platform, SenteraWeb. An Ethernet cable or a Wi-Fi network can be used to establish the connection. It allows remote monitoring of data and adjustment of settings for the connected HVAC devices via the internet. Data logging is also supported.
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