What are the air delivery modes and characteristics of Central air conditioning?
A Central air conditioning : one is the airflow organization method (i.e., where the air comes from and where it blows), and the other is the operation control mode (i.e., how to adjust the air volume and water temperature to control the temperature). The two have quite different characteristics.
I. Classification by airflow organization method (supply/return air location)
This refers to the physical airflow path caused by the installation location of Central air conditioning , which directly determines the uniformity of indoor temperature distribution.
Top-supply (top-down return) : The unit is concealed within the ceiling, supplying air downwards from the top, with return air returning through ceiling return air vents. Suitable for larger rooms with greater depth. However, it is important to note that the air velocity should be controlled below 0.2 m/s; otherwise, discomfort such as a hot head and cold feet may occur in winter.
Side-supply air (side supply and side return or top return) : This method often utilizes the difference in ceiling height between the corridor and the room, installing the unit in the ceiling closer to the room to supply air horizontally to the side. This method has less resistance loss and is quite effective in hotel and restaurant guest rooms.
Top-supply, bottom-return (blowing method) : For vertical units or specific structures, the airflow is delivered from the top and returns from the bottom after descending. This method is suitable for rooms with ample space.
Top-to-bottom airflow method (exhaust ventilation) : Airflow returns from the top, is processed, and then delivered from the bottom. This method is suitable for rooms with limited installation space.
Air supply mode | airflow path | advantage | shortcoming | Applicable Scenarios |
Side delivery next time | Horizontal air supply via double-layer louvers on the upper side wall → jet air attached to the ceiling → recessed → return air via suspended ceiling below the unit. | Long air delivery distance (up to 3~5m), stable airflow, low noise, most commonly used | It occupies the upper space of the side wall and requires a suspended ceiling. | Bedroom, Office, Standard Guest Room |
Next time | Ceiling diffusers deliver air vertically downwards → directly into the personnel area → side return air. | Cool air reaches the personnel area directly, heating effect is good (hot air is directly pushed down), and temperature is uniform. | When cooling, the cold air blows directly onto your head, creating a blowing sensation. | Living rooms and lobbies with high ceilings (>3m) and high heating requirements |
Side delivery and side return | Air supplied from the upper part of the same side wall → Air returned from the lower part of the same side wall | It does not occupy the return air space under the ceiling, has a good decorative effect , and does not reduce the floor height. | Risk of short circuit in supply/return air, short airflow range | Integrated living room and TV wall design for villas with high decoration requirements |
Send to the previous post / Send to the previous post | After the unit delivers air, it travels a short distance along the ceiling, and the return air is also located at the top of the ceiling. | Flexible piping layout, suitable for small spaces | Airflow is prone to short circuits and uneven heating/cooling. | small spaces such as corridors and restrooms |
II. Classification by Operation Control Mode (Regulation Method)
This refers to the way users adjust the output of heat and cold through thermostats or system logic.
Automatic mode : The system automatically adjusts the water valve opening (controlling water temperature) and fan speed (controlling airflow) based on the return air temperature sensor to reach the set temperature as quickly as possible. Some systems also include an "energy-saving mode," which allows the supply air temperature to deviate slightly from the set value when cooling demand is low, reducing chilled water consumption and thus saving electricity.
Manual mode : Users directly set the fan speed to high, medium, or low, and the thermostat opens and closes the water valve according to the room temperature. This is the most traditional control method, where the fan speed is constant and the air temperature is adjusted solely by the water valve.
Idle mode : Commonly found in hotel rooms. When an occupancy sensor (such as a key card) detects that the room is unoccupied, the fan automatically switches to low speed and the set temperature is adjusted up (during the cooling season) or down (during the heating season) to save energy.
III. Classified by air outlet type (3 common types)
Wind vent | Appearance | Features |
Double-layer louvered air vent | Rectangular, with two layers of adjustable blades | The angle is adjustable up/down and left/right, side air supply is standard , and the attached jet effect is good. |
Square diffuser | Square-shaped multi-bladed, mostly with 3-4 diffusers. | Downward vertical air supply, standard configuration with both supply and return air , ensures uniform airflow and aesthetically pleasing design. |
Slit-type (linear) air outlet | Slender and long, it can be made several meters long. | Popular in modern minimalist interior design , this space offers even airflow, strong decorative appeal, and is suitable for large spaces. |
In summary : the airflow organization mode determines "where the wind blows," focusing on comfort and compatibility with the interior design; the operation control mode determines "how much electricity is used," focusing on temperature control accuracy and energy saving. In actual use, the two are combined.
