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  • Writer's pictureKai Zhang

What is VRV, FCU, AHU, PAU, RCU, MAU, FFU, HRV and HVAC in Air Conditioning System?


VRV System
VRV System

1. VRV: Variable Refrigerant Volume or VRF: Variable Refrigerant Volume Flow

The VRF/VRV is a one-to-many central air conditioning system. This system is consists of 1 outdoor unit and 2 or more indoor units. The outdoor unit is for air-cooled heat exchange, and the indoor units adopt the direct evaporative heat exchange.


FCU
FCU

2. FCU: Fan Coil Unit

The fan coil unit is the terminal device of the air conditioning system. It is for continuously recirculating the air in the room where the unit is located, so that the air is cooled (heated) after passing through the cold water (hot water) coil to keep the room temperature constant. It mainly relies on the forced action of the fan to heat the air when it passes through the surface of the heater, thus strengthening the convective heat exchanger between the radiator and the air, which can quickly heat the air in the room.



AHU
AHU

Air handling unit, also known as air conditioning box/cabinet. It mainly relies on the rotation of the fan to drive the indoor air to exchange heat with the internal coil of the unit, and to filter the impurities in the air, so as to maintain the indoor temperature, humidity and air cleanliness by controlling the outlet air temperature and air volume. The air handling unit with the fresh air function also performs heat and humidity treatment and filtering functions on the air including fresh air or return air. At present, air handling units mainly have several forms such as ceiling type, vertical type, horizontal type and combined type. Among them, the ceiling-type air handling unit is also called a hanging cabinet; the combined air handling unit is also called a combined air cabinet.


HRV
HRV

4. HRV: Heat Reclaim Ventilation

HRV is invented by Daikin Air Conditioning in 1992, it is now called the Total Heat Exchanger. This type of air conditioner recovers lost heat energy through ventilation equipment, reducing the load on the air conditioner while maintaining a comfortable and fresh environment. In addition, HRV can be used in conjunction with VRV systems, commercial split systems and other air conditioning systems, and can automatically switch ventilation modes to further improve energy-saving effects.


The FAU fresh air unit is an air-conditioning device that provides fresh air, and it is used for household and commercial use.

Working principle: Fresh air is drawn from the outside and sent to the room through the fan after dust removal, dehumidification (or humidification), cooling (or heating) and other treatments, and replaces the original indoor air when it enters the indoor space. The difference between AHU air handling unit and FAU fresh air unit: AHU not only includes the fresh air condition, but also includes the return air condition; FAU fresh air unit mainly refers to the air handling unit with fresh air condition. In a way, AHU includes FAU.


PAU
PAU

6. PAU: Pre-Cooling Air Unit

The pre-cooling air conditioning box is generally used in conjunction with the fan coil unit FCU. Its function is to pre-treat the outdoor fresh air and then send it to FCU.


7. RCU: Recycled Airhandling Unit

The circulating air conditioning box is also called the indoor air circulation unit, which mainly sucks and discharges indoor air to ensure indoor air circulation.


MAU
MAU

8. MAU: Make-up Air Unit

It is an air-conditioning device that provides fresh air. Functionally, according to the requirements of the use environment, it can achieve constant temperature and humidity or simply provide fresh air. The working principle is to extract fresh air outside. After dust removal, dehumidification (or humidification), cooling (or heating) and other treatments, it is sent to the room through the fan, and the original air in the room is replaced when it enters the indoor space. Of course, the functions mentioned above must be determined according to the needs of the use environment. The more complete the functions, the higher the cost.


9. DCC: Dry Cooling Coil

Dry cooling coils (referred to as dry coils or dry cooling coils) are used to remove sensible heat in the room.


10. HEPA: High-efficiency Particulate Arrestment

It refers to filter screens that meet the HEPA standard, with an efficiency of 99.998% for 0.1 microns and 0.3 microns. The characteristic of HEPA mesh is that air can pass through, but fine particles cannot pass through. It can remove more than 99.7% of particles with a diameter of 0.3 microns (1/200 of the hair diameter), and is the most effective filter medium for pollutants such as smoke, dust, and bacteria. It is an internationally recognized high-efficiency filter material. It has been widely used in high-clean places such as operating rooms, animal laboratories, crystal experiments and aviation.


FFU
FFU

11. FFU: Fan Filter Units

The fan filter unit is a terminal purification equipment that combines a fan and a filter (high-efficiency filter (HEPA) or ultra-high-efficiency filter (ULPA)) to form its own power. To be precise, it is a modular terminal air supply device with its own power and filtering function. The fan sucks air from the top of the FFU and filters it through HEPA, and the filtered clean air is evenly sent out at the wind speed of 0.45m/s±20% on the entire air outlet surface.


12. OAC: Outdoor Air Conditioner

OAC is a name called in Japan, which is used for air feeding into closed workshops, which is equivalent to fresh air treatment unit MAU or FAU.


EAF
EAF

13. EAF: Exhaust Air Fan

EAF air-conditioning exhaust fan is mainly used in the public areas of the floor, such as corridors, stair front rooms, etc.


14. HVAC: Heating, Ventilation and Air Conditioning System



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