Digital Compressor Upgrade: Addressing Multiple Retrofit Challenges

Digital Compressor Upgrade: Addressing Multiple Retrofit Challenges

Best Practices, Cost Saving, Efficiency, Performance / By Zach Moorse

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At Carlson & Stewart Refrigeration, Inc., we continuously strive to offer our clients advanced and efficient refrigeration solutions. One of the most significant advancements in recent years is the digital compressor upgrade, which addresses multiple retrofit challenges in commercial refrigeration systems. This upgrade preserves your capital investments by extending the lifespan of existing systems and achieving goals like improved system reliability, reduced energy consumption, true load matching, and precise temperature control.

Capacity Modulation: Mechanical vs. Digital Methods

Mechanical strategies to modulate compressor capacity offer varying degrees of effectiveness:

Uneven Rack Systems: Utilize a bank of compressors with different capacities (e.g., 20K, 40K, 60K BTUs) for improved load matching. However, these systems are prone to high cycling rates and cannot provide precise temperature control.

Variable-Speed Drives: Integrate variable-speed drives into the compression cycle to modulate capacity. While effective, they are often cost-prohibitive and offer a limited modulation range.

Benefits of Digital Capacity Modulation

Digital capacity modulation is a superior compression technology that allows for infinite capacity adjustments from 10 to 100 percent. This retrofit involves replacing one fixed-capacity compressor with a new digital compressor as the lead compressor, aiming to achieve load matching and energy benefits while minimizing the required modulation range. The process is straightforward and benefits from the latest technology and electronic controls to upgrade your existing refrigeration system.

Key Benefits:

Decreased Power and Energy Consumption: Significantly reduces energy usage, leading to lower electricity bills.

Reduced Compressor Cycling: Minimizes on/off cycles, extending the lifespan of the compressor.

Increased System Reliability: Enhances the reliability of the entire system by reducing mechanical wear and tear.

True System Load Matching: Adjusts the system’s capacity to match varying refrigeration loads accurately.

Precise Temperature Control: Maintains tight temperature ranges, essential for the quality and safety of perishable goods.

Addressing Trends in Supermarket Refrigeration

Digital upgrades are particularly beneficial for supermarket applications, where operators seek retrofit opportunities to tackle modern operational challenges. Here’s how digital capacity modulation can help supermarkets achieve their operational goals:

1. Improve Energy Efficiencies

Independent tests have verified the energy-efficiency benefits of replacing a fixed-capacity compressor with a digital model on a parallel rack. Tests show that simply installing a digital compressor can yield a 4 percent reduction in energy consumption. Activating digital capacity modulation capabilities can provide an additional 12 percent energy improvement, resulting in annual savings of $17,215.

2. Adding Doors to Open Display Cases

Open display cases consume the most refrigeration energy in supermarkets. Adding doors can reduce cold air loss, resulting in a 50–80 percent load reduction and significant energy savings. However, this can lead to an oversized refrigeration system. Digital capacity modulation allows the system to adapt to the reduced load, delivering additional efficiencies.

3. Achieve True Capacity Control

Engineers have long sought a system capable of matching fluctuations in supermarket refrigeration loads. Digital compressors with capacity modulation are the most effective method, proving less expensive and easier to install than variable-speed drives. Unfortunately, many system designers and contractors are unaware of the potential to retrofit existing systems for modulation from 10 to 100 percent.

Applicability in Foodservice

The foodservice sector shares many challenges with supermarkets. Restaurant operators are keen to retrofit or replace refrigeration systems to reduce energy consumption. Digital compression technology and capacity modulation are also effective in these applications. Typically, a multiplex architecture is used, where one digital compressor provides cooling for multiple fixtures within each temperature group. This setup allows precise capacity modulation in response to varying refrigeration loads.

Restaurants have successfully utilized this architecture to reduce annual energy costs by up to 33 percent. Operators also appreciate enhanced electronic controls that enable remote monitoring, alarms, and refrigeration management. Digital compression technology allows operators to accurately size refrigeration systems to their facility’s needs, making it a reliable method for reducing energy footprints.
A Full-System Approach to Efficiency

Operators can maximize the benefits of a digital compressor upgrade by deploying a full-system approach to efficiencies. Additional system components that can enhance digital capacity modulation capabilities include:

Case Controls: Provide precise temperature, defrost, variable compressor, and evaporator controls, capable of integrating with larger facility/building management systems.

Electronic Expansion Valves (EXVs): Enable accurate control of refrigerant flow and system superheat.

Low Condensing Operation: Allows systems to float head pressures according to changes in ambient temperatures, reducing energy consumption by up to 30 percent.

Upgrading your refrigeration rack system to utilize digital unloading compressors is a strategic move that offers numerous benefits, including enhanced energy efficiency, improved system performance, and significant cost savings. At Carlson & Stewart Refrigeration, Inc., we are committed to helping you leverage the latest advancements in refrigeration technology to optimize your operations. Contact us today to learn more about the benefits of digital compressor upgrades and how we can assist you in making this valuable transition.

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