Common Issues in the Design and Selection of Air Conditioning Units
Apr 27,2026
I. Selection of Energy Sources
Currently, the most common forms of energy utilization include screw chillers, centrifugal chillers, VRV systems, lithium bromide absorption chillers, modular air handling units, ice storage systems, tri-generation systems, municipal energy supplies, and heat pumps. However, our primary focus lies on energy conservation and emission reduction, low operating costs, environmental benefits, and the flexibility to adapt operations based on the specific energy source and load requirements. Therefore, in regions where industrial steam supply is available—or where oil prices are relatively stable and favorable—we may consider utilizing steam-driven lithium bromide absorption chillers. For relatively independent structures such as villas or resort complexes, modular chillers or VRV systems are often the preferred choices. For large-scale commercial and institutional buildings, screw chillers and centrifugal chillers are typically given priority. In scenarios where the peak-to-off-peak electricity price ratio reaches 4:1—and where the air conditioning load is characterized by significant intermittency—the adoption of an ice storage system may be considered. Furthermore, in regions where natural gas prices are low and supported by favorable energy subsidy policies, the implementation of a tri-generation system (combined cooling, heating, and power) may be a viable option.
II. Piping System Design for Air Conditioning Units
1. When designing the air conditioning piping system, it is advisable to prioritize a consistent piping layout—specifically, a closed-loop variable-flow system—and to install pressure-balancing valves between the supply and return headers of the main piping loop. This design approach effectively resolves issues related to excessively low temperatures at the system's lower levels during winter and excessively high temperatures at the upper levels during summer. Additionally, this configuration facilitates air venting within the system, simplifies integration with the Building Automation System (BAS), and resolves temperature differential issues between the terminal units and the front-end equipment.
2. In complex operational environments, a multi-zone parallel piping system—capable of simultaneously supplying both chilled and hot water—may be selected. In the East China region, considering the inherent complexity of such systems and the associated construction costs, a dual-mode control strategy is often adopted; however, this approach frequently proves insufficient to meet the stringent requirements of high-star-rated hotels during the transitional seasons of spring and autumn, when ambient temperatures fluctuate significantly. For instance, areas such as restaurants, KTV lounges, and fitness centers may require cooling, while guest rooms and conference halls simultaneously require heating. To address this challenge, the following operational strategy can be implemented: During the summer and winter seasons, all valves on the auxiliary supply and return headers are closed, allowing the main supply and return headers to handle the entire cooling or heating load. During the transitional seasons (spring and autumn), the main supply header valves leading to specific zones—such as ballrooms, fitness centers, and restaurants—are closed to cut off the chilled water supply; conversely, all valves on the auxiliary supply and return headers are opened to facilitate the circulation of hot water from the main heating loop. Thus, the main water distributor supplies heat to the room, while the auxiliary distributor provides cooling to the dining area and the gym. Additionally, butterfly valves may be utilized for the water inlet and outlet valves on the unit. Butterfly valves are characterized by their light weight, relatively compact footprint, clear open/closed indication, and simple, convenient operation. These attributes make them well-suited for installation, operation, maintenance, and safe usage. In air conditioning systems, butterfly valves are the preferred choice for most standard water valves exceeding a nominal diameter (DN) of 50.
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