In modern building and industrial air conditioning systems, various key components play different roles in system operation, air treatment, and temperature and humidity control. This article provides a detailed explanation of the differences and specific functions of PAU, MAU, AHU, RCU, DDC, FCU, and FFU.
1. AHU (Air Handling Unit) – Combined Air Handling Unit
Function
The AHU is mainly responsible for regulating air temperature, humidity, and cleanliness and is a critical part of central air conditioning systems. It typically consists of multiple sections, such as filtering, heating, cooling, humidification, dehumidification, and fan sections, processing a mix of return air and fresh air before delivering it indoors.
Features
- Handles indoor return air and partial fresh air.
- Adjusts air temperature and humidity through cooling or heating coils.
- Suitable for large-scale air conditioning needs, such as office buildings, shopping malls, and factories.
2. PAU (Primary Air Unit) – Pre-Cooling Air Handling Unit
Function
PAU is primarily used for pre-processing outdoor fresh air before delivering it to fan coil units (FCU) to reduce the load and improve the efficiency of the air conditioning system.
Features
- Mainly treats outdoor fresh air, improving air quality.
- Uses cooling or heating coils for initial temperature and humidity adjustment.
- Ideal for environments requiring high-quality fresh air, such as laboratories and hospitals.
3. RCU (Recycled Air Handling Unit) – Recirculation Air Handling Unit
Function
RCU functions similarly to AHU, but its primary role is to recirculate indoor air instead of introducing fresh air, helping to save energy and maintain stable indoor temperature and humidity.
Features
- Recirculates indoor air to reduce energy consumption.
- Commonly used in temperature-controlled environments, such as data centers and server rooms.
- Does not directly handle fresh air but reprocesses return air.
4. MAU (Make-Up Air Unit) – 100% Fresh Air Unit
Function
MAU is an air conditioning unit that exclusively handles fresh air, often used in environments requiring high-quality fresh air, such as hospitals, cleanrooms, and laboratories.
Features
- Only processes outdoor fresh air without mixing return air.
- Can include humidification, dehumidification, and filtration for temperature and humidity control.
- Suitable for environments with strict air quality requirements, such as electronics manufacturing and the pharmaceutical industry.
5. DDC (Direct Digital Control) – Direct Digital Control System
Function
DDC is an intelligent control system for central air conditioning, used to precisely control the operation of air conditioning equipment such as fans, cooling coils, and pumps, optimizing performance and energy efficiency.
Features
- Uses digital control technology to improve precision.
- Can be integrated into Building Automation Systems (BAS) for remote monitoring and management.
- Enhances system efficiency and reduces energy consumption.
6. FCU (Fan Coil Unit) – Terminal Fan Coil Unit
Function
FCU is mainly used for local room temperature control, adjusting air temperature by passing it through cold or hot water coils. It is one of the terminal units in central air conditioning systems.
Features
- Suitable for zoned air conditioning, such as hotel rooms, offices, and residential areas.
- Uses a fan to circulate air and passes it through coils for cooling or heating.
- Allows independent temperature control, improving flexibility.
7. FFU (Fan Filter Unit) – Fan & Filter Integrated Unit
Function
FFU is primarily used in air purification systems, combining a fan and HEPA or ULPA high-efficiency filters. It is widely applied in cleanrooms, laboratories, and other high-purity environments.
Features
- Self-contained fan and filter, capable of independent operation.
- Filters dust, bacteria, and other pollutants from the air to provide ultra-clean air.
- Commonly used in semiconductor manufacturing, biopharmaceuticals, and laboratories.
Summary: Key Differences Between These Units
| Equipment | Main Function | Air Type Processed | Applicable Scenarios |
|---|---|---|---|
| AHU | Combined air handling unit, regulates temperature and humidity | Fresh air + Return air | Commercial buildings, factories, hospitals |
| PAU | Pre-treatment of fresh air | Fresh air only | Offices, hotels |
| RCU | Recirculates indoor air, processes return air | Return air only | Data centers, server rooms |
| MAU | 100% fresh air handling unit | Fresh air only | Hospitals, cleanrooms |
| DDC | Digital control system for air conditioning | Controls the entire system | Building automation |
| FCU | Terminal fan coil unit for local air conditioning | Indoor air | Hotels, residential spaces |
| FFU | Fan and filter integrated unit | Ultra-clean air | Cleanrooms, biopharmaceuticals |
Each of these components plays a different role in a central air conditioning system. Proper selection and combination of these units can improve system efficiency, enhance air quality, and reduce energy consumption.