In the heating and ventilation market and air-conditioning water machine systems, you often hear strange names for series of products such as FCU, AHU, PAU, RCU, MAU, FU, HRV, FAU, OAC and EAF. So, what do these letters represent this concept? What are their differences?

1. FCU (full name: Fan Coil Unit)

The fan coil is the terminal equipment of the central air conditioning system. The working principle is that the air in the bedroom is continuously recirculated in the unit, so that the air is cooled (heated) through the cold (boiled) water fan coil to maintain the stability of the indoor temperature. . Relying on the forced effect of the fan, the air is heated when passing through the surface of the electric heater, thereby strengthening the heat convection heat exchanger between the heat pipe radiator and the air, which can quickly warm the air in the bedroom.

2. AHU (full name: Air Handling Units, air handling units)

Air treatment unit, also called air conditioning unit, box fan. It mainly relies on the rotation of the fan to promote heat exchange between the air in the room and the fan coil inside the unit, and removes impurities in the air to maintain indoor temperature, humidity and air cleanliness levels by reducing the air inlet temperature and exhaust volume. The air treatment unit with fresh air system function also performs sensible heat treatment and filtering treatment on the air including fresh air system or supply air. At this stage, air treatment units mainly include ceiling-mounted, column-type, vertical and combined types. Among them, the ceiling-mounted air treatment unit is also called a wall cabinet; the combined air test unit is also called a combined wind cabinet or group cabinet.

3. HRV air handling unit

HRV, full name: Heat Reclaim Ventilation, Chinese name: kinetic energy recovery exhaust system. Invented for Daikin central air conditioning in 1992, it is currently called "air handling unit". This kind of air conditioner recycles lost heat through ventilation and cooling equipment, reducing the air conditioning load while ensuring a comfortable and refreshing environment. In addition, HRV can be used with VRV systems, commercial split systems and other air conditioning units, and will automatically change ventilation modes to further improve energy saving effects.

4. FAU (full name: Fresh Air Unit, fresh air system unit)

The FAU fresh air system unit is an air conditioning equipment that provides fresh air, and is available for residential and commercial use.

Principle: Fresh air is extracted outdoors and sent to the room by a fan through operations such as dust removal, dehumidification (or humidification), temperature reduction (or temperature increase), etc., and the original air in the room is replaced when it enters the indoor space design. The difference between AHU air treatment unit and FAU fresh air system unit: AHU not only includes the working status of the fresh air system, but also includes the air supply working status; FAU fresh air system unit mainly refers to the air treatment unit including the working status of the fresh air system. From a certain perspective, the former includes the latter.

5. PAU (full name: Pre-Cooling Air Unit, quenching air conditioning unit)

The quench air conditioning unit is generally used in conjunction with the fan coil unit (FCU). Its function should be to prepare the outdoor fresh air system and then send it to the fan coil unit (FCU).

6. RCU (full name: Recycled airhandling Unit, circulating system air conditioning unit)

Circulation air conditioning unit, also called room air circulation unit, usually sucks in and discharges room air to ensure room air circulation.

7. MAU (full name: Make-up Air Unit, brand new fan unit)

The new fan unit is an air conditioning device that provides fresh air. In terms of performance, according to the needs of the usage scenario, it can achieve constant temperature and humidity equipment or simply provide fresh air. The principle is to extract fresh air outdoors, and then send it to the room by a fan through operations such as dust removal, dehumidification (or humidification), temperature reduction (or temperature increase), etc., and then replace the original air in the room when it enters the indoor space design. Of course, the functions mentioned above depend on the needs of the use scenario. The more complete the basic functions, the greater the project cost.

8. DCC (full name: Dry Cooling Coil, dry test cooling coil)

Dry testing of cooling coils (called dry coils or drying fan coils) is used to remove indoor heat.

9. HEPA efficient air supply outlet

High-efficiency filter refers to a HEPA-standardized filter with a high efficiency of 99.998% for 0.1 μm and 0.3 μm. The characteristic of HEPA net is that air can pass through, but tiny particles cannot. Its removal efficiency can reach over 99.7% for particles with a diameter of about 0.3μm (1/200th of a hair’s diameter) and is the most effective filtering medium for harmful substances such as smoke, dust and germs. This is a highly efficient filtration raw material recognized by countries around the world. It has been widely used in high-line cleaning sites such as clinics, animal laboratories, crystallization experiments and airlines.

10. FFU (full name: Fan Filter Units, fan filter unit)

The fan filter unit combines a fan and a filter device (high-efficiency air outlet (HEPA) or ultra-high-efficiency filter (ULPA)) to form a tail-end oil fume purifier that increases its power. To be precise, it is a modular rear exhaust device with built-in driving force and filtering effect. The fan sucks in the air from the top of the FFU and filters it through HEPA. The filtered clean air is evenly sent out on all air outlet surfaces at an air volume of 0.45m/s ±20%.

11. OAC outdoor air treatment unit

OAC outdoor air treatment unit is the Japanese name for being sent into closed industrial plants. It is equivalent to China's fresh air system treatment unit MAU or FAU.

12. EAF (full name: Exhaust Air Fan, exhaust fan)

EAF central air-conditioning exhaust fans are mainly used in public places on floors, such as aisles and treatment rooms in front of indoor stairs.