When it comes to cooling solutions in HVAC systems, Direct Expansion (DX) equipment is a flexible problem solver. DX systems are a type of cooling system where the refrigerant is directly responsible for cooling the air. This technology compresses refrigerant, which then expands in the evaporator coil, absorbing heat from the surrounding air to provide cooling. The DX units often sit outside a building, similar to residential air conditioning systems, where they use ambient air to cool the condenser.
The Role of DX in Commercial HVAC Projects
Greg Munter, Partner, and Sales Engineer, PE, at Coward Environmental Systems, Inc. (CESI) sees many ways to use DX In commercial applications. “DX systems meet specific cooling requirements for large facilities working as standalone conditioner in a larger system,” he says. “This can provide flexibility, redundancy, and unique conditions for building that can sometimes amount to a cost savings overall to a project.鈥�
Custom DX Applications
100% outside air (OA) units are designed to manage outdoor air exclusively, conditioning it before introducing it into the indoor environment. Traditionally DX systems are not well suited for 100% OA applications.聽 Custom DX systems can provide an effective solution for 100% OA applications where other infrastructure is not available. According to Munter, “DX systems serve as excellent supplementary options for achieving a more customized approach, especially when addressing high-efficiency requirements or low-temperature discharge needs.”
The flexibility of DX systems makes them particularly valuable in mission-critical environments like data centers. “These facilities often rely on chilled water systems due to their superior efficiency and precise control. Yet, in such settings, DX systems are frequently implemented as a reliable backup solution.” Munter elaborates, “In situations like these, backup DX systems are integrated with emergency generators to ensure continuous cooling. This is essential when the primary chilled water system becomes unavailable during a power outage. Large chillers, although efficient, demand substantial energy, making them less suitable for operation with backup generators. In contrast, DX units can be standalone and require less energy than the whole chilled water system. They can run on generator power.”
This dual-system approach enhances the reliability of cooling systems in critical facilities and provides a level of redundancy that is vital for maintaining operations during unexpected disruptions. By incorporating DX systems as a backup, facilities can safeguard against the potential consequences of a primary system failure, ensuring that cooling is maintained under all circumstances.
Sometimes, units must be placed in interior spaces. In high-rise buildings or locations where outdoor placement of condensers is impractical, DX systems with ducted condensers or water-cooled condensers are used. “Ducted DX units can be a great solution for these applications,” Munter notes. “These systems are designed to be placed indoors, with air ducts facilitating the movement of cooling air through the condenser, allowing heat to be rejected outside. So, you can place them in interior utility rooms where outdoor space on the roof or on grade is not available.聽 Having the DX condensing unit inside the building can save a lot of environmental wear and tear on the condensing unit, often extending the life cycle of DX condensing unit.鈥�
DX units also offer the option of split air tunnel units. “Maintenance in HVAC systems often requires shutting down the unit, which can be problematic for mission-critical operations,” Munter notes. “To address this, split air tunnel units divide the airflow into separate sections. This design allows one section to be serviced while the other continues to operate, maintaining air circulation without complete system downtime.”
Replacement Applications
When it comes to replacing HVAC units, some locations demand an exact match to the existing setup. This need arises from various factors, including the architecture of the building, historic preservation concerns, or simply maintaining consistency across a property. However, achieving this exact match can be challenging due to several fundamental changes in the HVAC industry over the years.
“One of the primary challenges in replacing older units is the evolution of refrigerant types,” says Munter. “As have tightened, many older refrigerants have been phased out in favor of more eco-friendly options. This shift means that newer units often use different refrigerants, making it difficult to find a direct replacement for an outdated system.”
Efficiency standards have also undergone significant changes. “Modern HVAC units are designed to meet higher efficiency benchmarks, which not only reduces energy consumption but also affects the design and operation of the units,” he adds. “These changes can result in size, configuration, and performance differences compared to older models.”
Moreover, design improvements in HVAC technology have led to more compact and efficient units, but this progress can pose challenges when trying to match an older system’s footprint and connections. The original configuration of many HVAC systems may no longer be in production, complicating the replacement process.
Custom-designed DX units offer a practical solution to address these challenges. As Munter explains, “With DX units, it is possible to create custom footprint units that are engineered to fit the specific needs of a replacement project. This customization allows for a seamless transition, even when the original configuration is no longer available. By engineering units that match the existing footprint and connections, custom DX units ensure the replacement process is smooth, minimizing disruption and maintaining the integrity of the building’s HVAC system.”
Want to Learn More about DX Units?
DX systems offer a versatile cooling solution for a variety of specialized HVAC applications. Whether it’s in high-stakes environments like data centers or in projects requiring custom designs, DX technology provides reliable and efficient cooling that meets the demands of modern commercial and industrial needs. Coward Environmental Systems, Inc. represents several leading manufacturers of DX systems. Contact us today to find out more.
