The use of a digital compressor as the lead compressor in a fixed capacity refrigeration rack is becoming a preferred method for supermarkets seeking to meet varying refrigeration loads. With the ability to modulate capacity from 10 to 100 percent, digital compressors are now being written into the design specifications of many big-box retailers.
Digital Upgrade Kit for Traditional Rack Systems
This option is also available as an upgrade to existing refrigeration systems that are based on traditional parallel rack architectures. Many technicians are being called upon to retrofit these systems with a digital compressor upgrade kit. Although there are some newer technologies and electronic controls involved with the transition, the upgrade process is relatively straightforward:
- Identify the compressor
- Verify the system controller
- Choose the correct upgrade model
- Select the digital controller
- Install upgrade kit
Digital Technology Yields Indisputable Results
A single digital compressor with 10 to 100 percent capacity modulation enables continuous variable unloading that delivers immediate and significant benefits. While results vary per application, operators can expect improvements in three major categories:
- Reduced compressor cycling— the average compressor cycling is reduced up to 50 percent, but some scenarios have seen cycle counts go from 900 starts per day to 12 starts across a four-day span
- Improved temperature control— digital modulation is capable of temperature control within +/- 1 °F
- Tighter suction pressure control — operating suction pressure ranges are significantly reduced, moving from double-digit suction pressures (psig) to single-digit levels
These results make an open and shut case for a digital compressor upgrade. As awareness of this option becomes more well-known, many supermarket operators will opt for capacity modulation using this relatively simple upgrade to their existing rack systems.
Other Methods of Capacity Modulation
The challenge of modulating capacity in centralized rack refrigeration systems is not a new one, and system designers have made several attempts to solve the problem. Though none are as effective as digital capacity modulation, technicians still frequently encounter uneven rack and variable speed drives.
One digital compressor per suction group can provide precise capacity modulation from 10 to 100 percent. The results are up to 50 percent reduction in compressor cycling, improved equipment reliability and precise temperature control.
This blog is a summary of the article Make the Upgrade to Digital from our recent edition of E360 Outlook.