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Nonresidential Refrigeration System Opportunities

Measure Description

The California Energy Code (Title 24, Part 6) currently includes mandatory efficiency requirements for refrigeration systems serving refrigerated warehouses and retail spaces with walk-in coolers or freezers or refrigerated display cases. This measure proposes code change proposals that will improve energy performance end reduce greenhouse gas (GHG) emissions from refrigeration systems in refrigerated warehouse, retail stores, and commercial kitchens. Requirements for commercial kitchens would apply to a variety of building types including restaurants, schools, and hospitals. 

Submeasure A: Design and Control Requirements for Transcritical CO2 Systems

Transcritical CO2 refrigeration systems are a growing technology alternative for owners seeking low global warming potential (GWP) refrigeration systems utilized in commercial refrigeration and refrigerated warehouses. Due to its low critical point of 87°CO2 as a refrigerant requires unique design and control requirements compared to other refrigeration systems with more common refrigerant types (ammonia, halocarbons). The proposed code changes provide the first code requirements in Title 24, Part 6 for these system types to clarify best practices for designers and owners. 

Submeasure B: Minimum Air-Cooled Condenser Sizing and Specific Efficiency for Packaged Refrigeration Systems

Packaged refrigeration systems combine all the components of a refrigeration system into modular units that can be distributed around a building to replace large centralized systems. They typically use ammonia as the refrigerant but avoid the need for a large single charge, thus providing refrigerated warehouse owners an option for a low GWP refrigeration system.  

A market study was conducted to understand how current code requirements originally designed for large central systems affect the design and cost effectiveness of packaged systems. The proposed code changes would reduce the minimum size requirement for air cooled condensers for these systems to make them more cost effective. 

Submeasure C: Evaporator Specific Efficiency

In a mechanical refrigeration system, the evaporator is the component that absorbs heat from the air inside the space being cooled. Evaporator efficiency is based on the amount of heat it can absorb divided by the amount of power that must be consumed by the fan motors which are used to evenly distribute the cool air throughout the space. A market study was conducted to understand the efficiency of available products, and a cost-effectiveness analysis was performed to establish reasonable minimum evaporator specific efficiency thresholds that result in statewide energy savings. 

Submeasure D: Automatic Door Closers

The proposed code changes add requirements for automatic door closers for refrigerated warehouses to further reduce infiltration. Infiltration occurs when warmer air enters the space being cooled and can account for up to 30 percent of refrigeration loads in refrigerated warehouses. High amounts of infiltration load place a higher load on mechanical refrigeration systems and thus result in wasted energy.   

Submeasure E: Acceptance Testing for Commercial Refrigeration

Requirements for commercial refrigeration systems have been included in Title 24, Part 6 since 2013. However, acceptance testing for key energy savings requirements has not yet been included in the reference appendices. Without acceptance testing procedures, installations in California may not be in full compliance resulting in an increase in statewide energy usage. This Draft CASE Report proposes acceptance testing procedures to improve future compliance. 

Proposed Code Changes 

Submeasure A: Design and Control Requirements for Transcritical CO2 Systems

The proposed code changes would result in the following requirements for transcritical CO2 refrigeration systems utilized in commercial refrigeration and refrigerated warehouses: 

  • Restrictions on air-cooled gas coolers in high ambient temperature climate zones to reduce the number of supercritical operating hours. Alternatives to air cooled gas coolers include water cooled condensers connected to a cooling tower, adiabatic gas coolers, and evaporative gas coolers.  
  • Restricted Climate Zones for Refrigerated Warehouses: Climate Zone 2, 4, 10, 11, 12, 13, 14, and 15 
  • Restricted Climate Zones for Commercial Refrigeration: Climate Zone 10, 11, 12, 13, 14, and 15 
  • Minimum air-cooled and adiabatic gas cooler sizing and specific efficiency. This is to ensure costeffective design of the refrigeration system’s heat rejection equipment, balancing first cost of the equipment and the additional energy savings that are achieved with larger heat exchanger surfaces. 
  • Supercritical optimized head pressure control, which allows for the head pressure setpoint to be reset in response to ambient conditions 
  • Ambient temperature reset control strategy to control head pressure during subcritical operation 
  • Minimum saturated condensing temperature of 60°F for systems with design saturated suction temperatures of less than 30°F (otherwise 70°F) 
  • Heat recovery for transcritical COsystems in supermarkets. Refrigeration equipment in supermarkets creates a heating load to maintain comfortable space temperatures for shoppers. As a result, supermarkets require heating for more hours than most occupancies. In most climate zones, waste heat from the refrigeration system can be recovered to provide it more efficiently. Heat recovery is already required for other refrigeration technologies, but heat recovery equipment for high pressure CO2 systems have different costs and savings. 

Submeasure B: Minimum Air-Cooled Condenser Sizing and Specific Efficiency for Packaged Refrigeration Systems 

The proposed code change would decrease the minimum sizing and specific efficiency requirements for air cooled condensers that are integrated into a large packaged refrigeration system. The code language would also exempt packaged units below a certain compressor horsepower, similar to the existing exemption for condensing units below a certain size.   

Submeasure C: Evaporator Specific Efficiency

The proposed code change would set a minimum evaporator specific efficiency in non-process cooling/freezing applications in refrigerated warehouses. Only units with efficiencies in the top 60th percentile, based on an extensive market study, would be allowed.

Submeasure D: Automatic Door Closers

The proposed code change would require two types of automatic door closers to be installed on doors in refrigerated warehouses that separate a colder freezer, cooler, or dock space from a warmer temperature space or the outside. These two door types are an automatic hinge that closes the door from an open position, as well as a tight sealing mechanism that closes the door completely if slightly ajar (approximately one inch opened).  

Submeasure E: Acceptance Testing for Commercial Refrigeration

The proposed acceptance testing procedures for commercial refrigeration add new language added to the Nonresidential Appendix NA7 to cover the following measures: 

  • Condensers and Condenser Fan Motor Variable Speed Control (air cooled, evaporative cooled, and adiabatic) 
  • Compressor Floating Suction Controls 
  • Liquid Subcooling 
  • Refrigerated Display Case Lighting (motion sensor and automatic time switch controls) 
  • Refrigeration Heat Recovery 

Relevant Documents

Measure proposals, supporting documents, and other outside references will be made public as they become available.

Round Two Utility-Sponsored Stakeholder Meeting Materials

Round One Utility-Sponsored Stakeholder Meeting Materials

Provide Feedback

Draft CASE Report Now Available (Comments accepted until July 17, 2020)

This measure description will be updated as research is developed to support the 2022 code cycle. For questions or suggestions, email Include the measure name in the subject line.

Give Us Your Feedback

The Statewide CASE Team values input from all stakeholders engaged in the Title 24, Part 6 code change process. We encourage the open exchange of code change comments and concerns.

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