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Optimize Supermarket Energy Efficiency and Performance With VFD Retrofits

Joe Summers | Senior Product Manager – Scrolls & Drives
Emerson’s Commercial & Residential Solutions Business

The use of fixed-speed (or fixed-capacity) refrigeration systems and HVAC rooftop units (RTUs) is a common strategy in the U.S. food retail sector. If you went into the machine rooms of most grocery stores, you likely would find centralized, direct expansion (DX) refrigeration systems with parallel racks of fixed-speed compressors. On the rooftops, you would find RTUs with air-handler blowers running continuously at full speeds. Varying the capacity of these critical units relies on mechanical throttling techniques that consume energy, cause excess equipment wear, but never quite achieve the desired load matching. In a new white paper, Emerson explore how operators can retrofit these systems with variable frequency drives (VFDs) to deliver significant energy efficiency and performance improvements.

For the most part, the potential uses for VFDs in the food retail sector have been largely unexplored. Simply put, VFD retrofits allow operators to convert existing fixed-speed equipment — such as compressors, fans or pumps — to enable variable-capacity modulation. Benefits include:

  • Reduced energy consumption and electricity costs
  • Improved load matching, temperature precision and performance
  • Extended equipment reliability lifespan

VFDs in refrigeration systems

The inability to match the refrigeration capacity to fluctuating evaporator load demands is a known limitation of parallel rack systems with fixed-speed compressors. Systems are designed and specified to accommodate peak-load conditions and provide reliable cooling during the hottest days of a year — i.e., they’re essentially over-sized for lower load conditions and cooler periods.

Widely varying load requirements, ever-changing ambient conditions and variations in defrost cycles can create undesirable fluctuations in case temperatures. Compressors are constantly switching off and on to try and adapt to these changing demands, which can accelerate wear on system components, increase the potential for food quality issues, and consume excess electricity.

VFDs give operators and service technicians an effective method for alleviating fixed-speed compressor motor challenges and achieving the benefits of variable-capacity modulation. By retrofitting a VFD to the lead compressor in every parallel compressor rack, each lead compressor can then modulate the capacity of the entire rack. This enables fixed-speed compressors to handle the base load, while leveraging the VFD-equipped lead compressor to manage fluctuations in demand. Compared to a traditional fixed-speed approach, this results in:

  • Reduced cycling on/off strain and an extended life of the lead compressor
  • Smoother and almost constant system suction pressure
  • More consistent evaporator (case) temperatures and humidity conditions

Validating VFD ROI in HVAC case study

In HVAC RTUs, air-handler blower capacity is also designed to handle the peak cooling conditions of the installation’s summer season. But as building loads fluctuate widely throughout the year, HVAC systems often operate at only a fraction of their design capacity. Thus, air-handler blower fans run continuously at full, fixed speeds, regardless of load requirements. Technicians often use a mechanical throttling technique to help reduce airflow, but this results in increased energy consumption and a reduction in the equipment’s lifespan.

Retrofitting a VFD onto an existing fan motor allows it to modulate capacity based on varying load requirements — full speed during peak-load periods and slower speeds when less load is required. In this HVAC RTU application, variable-capacity modulation delivers a fast return on investment (ROI) via a non-linear, speed-to-power ratio. By slowing down a blower motor fan speed by 25 percent of its normal operating rate, it’s estimated that facility operators can reduce energy consumption by 50–60 percent.

Emerson validated this principle recently by installing Copeland™ VFDs on a food retailer’s existing rooftop HVAC air-handler blower motors in 78 of their stores. Results included:

  • Reduced energy consumption by 52 percent
  • Saved more than $800,000 in electricity costs
  • Equivalent to adding $10M in sales at an 8 percent margin

Retrofit with Copeland VFDs

Emerson is committed to helping food retailers and technicians to simplify the retrofit process in HVACR applications and improve equipment reliability, performance and efficiency. Copeland VFDs, EVM/EVH Series are designed to reduce the costs and complexities of VFD implementation:

  • The Copeland EVM Series is ideal for chillers, medical refrigeration, display cases, walk-ins and reach-ins.
  • The Copeland EVH Series is designed for large, centralized racks (including CO2), HVAC applications, advanced chillers and industrial refrigeration applications.

Learn more about applying our VFD solutions to your HVACR operations by visiting our webpage.

Retrofit and Remodel Strategies to Achieve Lower-GWP Refrigeration

Andre Patenaude | Director – Solutions Integration,

Emerson’s Commercial and Residential Solution’s Business

Three decades ago, supermarket operators had few options for selecting environmentally friendly refrigeration strategies. Now, as they look to retrofit or remodel older systems to comply with environmental regulations or achieve corporate sustainability goals, operators face an expanding selection of refrigeration architectures driven by the transition to lower-global warming potential (GWP) refrigerants. In a recent article that was published in Contracting Business, I explored several options that are available to supermarkets seeking a path to low-GWP refrigeration.

Lower-GWP refrigerant options continue to proliferate

Refrigerant selection is one of the most influential factors in a retrofit or remodel strategy, often serving as an underlying process to help operators achieve corporate sustainability goals. But refrigerant selection also dictates everything from refrigeration architecture to servicing requirements to the total cost of ownership (TCO).

As the U.S. continues to phase down the use of high-GWP refrigerants and phase out those with ozone depletion potential (ODP), manufacturers are beginning to utilize a variety of alternative refrigerants that offer varying degrees of GWP reduction. Of those that are considered both safe and approved for use, the following offer distinct advantages in support of sustainability:

  • R-448/449A (low-GWP option) — Designed as a substitute for R-404A, R-448A offers a 65% reduction in GWP.
  • R-513A (lower-GWP option) — R-513A, a substitute for R-134a, delivers a 56% reduction in GWP.
  • A2L and A3 (lower- to lowest-GWP) — Mildly flammable A2L and flammable A3 (aka R-290 or propane) refrigerants are primarily used in self-contained systems and offer some of the most significant GWP reductions, and are some of the lower and lowest GWP options currently available,
  • CO2 aka R-744 (lowest-GWP option) — Used only in systems designed to handle its unique properties, R-744 is a natural refrigerant with a GWP of 1.

Upgrading for a more sustainable future

Retrofitting or remodeling a refrigeration system to improve sustainability or comply with regulations is not simply a matter of selecting a lower-GWP refrigerant. Operators must also evaluate different refrigeration systems to determine how to meet their sustainability objectives and select a system that aligns with their operational priorities. At Emerson, we refer to this process as the Six S’s of evaluation criteria:

  • Simple — to own and operate
  • Serviceable — aligns with maintenance and operations capabilities
  • Secure — provides safe operation and data security
  • Stable — delivers reliable, dependable performance
  • Smart — is equipped with electronic controls and connectivity to provide operational data and insights
  • Sustainable — from financial, technical and environmental perspectives

In terms of retrofits and remodels, the following architectures are emerging as the leading options for meeting the wide range of operator preferences:

  • Retrofit to R-448A/R-449A in existing centralized direct expansion (DX) systems — Replacing R-404A with R-448A allows operators to achieve significant sustainability improvements while preserving their existing system investments.
  • Remote/outdoor condensing units (distributed) — Remote condensing units offer installation flexibility and reliability while using low-GWP R-448A. They are ideal for small, urban store formats or for large supermarkets deploying new refrigeration capabilities outside of their existing DX systems.
  • Distributed systems — Operators can install multiple mini-racks or scroll packs in proximity to different refrigerated sections of a store. Using R-448A in this architecture can significantly reduce overall refrigerant charge while providing increased system reliability and energy efficiency.
  • Macro-distributed systems (self-contained) — Used in large cases that integrate a single compressor, refrigeration circuit and electronic controls present a simple, flexible, stand-alone option for retrofits and remodels. This approach can be scaled from one to multiple units.
  • Distributed scroll booster — This emerging distributed architecture uses low-pressure, lower-GWP R-513A for low- (LT) and medium-temperature (MT) circuits. A distributed scroll booster delivers improved energy efficiency and high reliability without added service complexities.
  • CO2 transcritical booster — A CO2 transcritical booster system is an environmentally friendly alternative to high-GWP, centralized DX systems. While this architecture uses the refrigerant CO2 (R-744) for LT and MT loads, its unique performance characteristics increase both system complexities and TCO.

Ready to meet current and future needs

The decision to retrofit or remodel a refrigeration system must be made with a long-term perspective. Operators should expect to get 20 to 30 years of service from their refrigeration systems with proper maintenance and care. But the uncertainty caused by shifting environmental regulations, changing consumer expectations and ever-evolving technologies can complicate the planning process.

Emerson is committed to providing operators with the tools and insights to meet this challenge head-on. We offer an array of compressors, condensing units, case controls and facility management technologies that can help operators to meet sustainability goals, comply with evolving regulations, and reduce the total equivalent warming impact (TEWI) of their refrigeration systems. We are also creating solutions that enable operators to make the transition to lower- and lowest-GWP refrigerants in ways that support their sustainability initiatives and long-term goals.

To learn more about how Emerson compressors and refrigeration technologies support different remodel and retrofit scenarios, read the full article.

 

What’s Behind the Door?

Retrofitting open display cases with doors

The short answer is ENERGY! Most retailers recognize that refrigerated display cases with doors use a lot less energy than open display cases.  The Better Buildings Alliance recently published a useful guide on retrofitting open refrigerated display cases with doors.  Adding doors to open cases greatly reduces cold air loss, which results in a 50-80% load reduction and significant system energy savings.  Additional benefits include increased shopper comfort, increased product life, and reduced product losses.  Retailers initially feared that adding the glass display doors would hurt the merchandising effort, but the vertical display has in many cases improved merchandising.

The refrigeration load will drop significantly after adding doors, so it makes the most sense for the existing refrigeration system to modulate to adjust to the lower load at all outdoor ambient conditions.  Controls on the anti-condensate (anti-sweat) door heaters will ensure that extra energy is not wasted here.  The retrofit process is a good opportunity to make additional energy upgrades to the cases, including lighting and fan upgrades.

The complete 33-page guide can be download for free from: Guide for the Retrofitting of Open Refrigerated Display Cases with Doors

Refrigerated Display Case with DoorsThe report breaks down best practices and guidelines for conducting case retrofits by project stage, from initial planning through project completion and system monitoring. The guide highlights the following areas of the process:

  • Retrofit Planning
  • Case Modification and Door Retrofit
  • Refrigeration-System Reconfiguration
  • System Performance Evaluation
  • Monitoring and Follow-Up

The ACHR NEWS has also taken note of this report on retrofitting display cases with doors.  They recently published the first of a five-part series providing a guide for retrofitting open refrigerated display cases with doors. This first part provides an introduction and background on the topic. The second part of this series, which will be published in June, will focus on retrofit planning. The July installment will deal with case modifications and door retrofits. The August article topic will be refrigeration system reconfigurations. The final installment in September will deal with system performance evaluation.  http://www.achrnews.com/articles/123075-an-open-and-closed-case-an-introduction

In this case, you can’t tell what’s behind the door until you put one on!

Craig Raney
Director of Marketing, Refrigeration
Emerson Climate Technologies

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