The differences and functions of MAU, AHU, RCU, DDC, FCU, DHU, PAU and FFU in air conditioning systems

AHU

Combined air conditioning unit: mainly extracts indoor air (return air) and some fresh air to control the outlet air temperature and air volume to maintain the indoor temperature.

PAU

Pre-cooling air conditioning box: The Primary Air Unit pre-treats outdoor fresh air before sending it to the fan coil unit (FCU).

RCU

(Recycled air handling unit) is a circulating air conditioning unit.

MAU

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

DCC

Dry cooling coil (abbreviated as the dry coil or dry cooling coil): is used to eliminate indoor sensible heat.

Direct Digital Control

HEPA Filter

The filter that meets HEPA standard has an efficiency of 99.998% for 0.1 micron and 0.3 micron. The characteristic of HEPA filter is that air can pass through, but fine particles cannot pass through. It can remove particles with a diameter of 0.3 micron (1/200 of the diameter of hair) at an efficiency of more than 99.7%, and is the most effective filter medium for pollutants such as smoke, dust and bacteria. (The diameter of smoke particles produced by smoking is 0.5 micron) 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.

FCU

Fan coil unit: Fan Control Unit Fan coil unit is the terminal device of air conditioning system. Its working principle is to recirculate the air in the room continuously in the unit, 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 passing through the heater surface, thus strengthening the convection heat exchange between the radiator and the air, and can quickly heat the air in the room.

VAV 

Variable air volume air conditioning system (VAV) control principle: The variable air volume controller and the room thermostat together constitute indoor cascade control, using indoor temperature as the main control quantity and air flow as the auxiliary control quantity. The variable air volume controller compares the difference between the actual temperature detected by the room temperature sensor and the set temperature, and outputs the adjustment signal of the required air volume to adjust the air valve at the end of the variable air volume, change the air supply volume, and keep the indoor temperature within the set range. At the same time, the air duct pressure sensor detects the pressure change in the air duct, adopts PI or PID regulation, and controls the speed of the variable air volume air conditioner fan through the inverter to eliminate the influence of pressure fluctuations and maintain the air supply volume.

DHU

DHU means "low humidity air conditioning unit" in Chinese. Low humidity air conditioning unit is a highly efficient and fast air dehumidification equipment, mainly composed of a dehumidification wheel unit, regeneration heating system, processing fan, regeneration fan, front and rear surface cooler, electric control cabinet and casing to form a box-type unit. The box body material adopts a double-layer plastic-coated color template, and the interlayer is filled with polyurethane foam insulation material, which can effectively prevent the temperature and humidity interference of the outside air.

FFU

Fan Filter Units, in Chinese, means "fan filter unit (unit)". That is, the fan and filter (HEPA filter (HEPA) or ultra HEPA filter (ULPA)) are combined to form a terminal purification device that provides its own power. To be precise, it is a modular terminal air supply device with a self-power and a filtering effect. The fan inhales air from the top of the FFU and filters it through the HEPA. The filtered clean air is evenly delivered at a wind speed of 0.45m/s±20% on the entire air outlet surface.