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 9, 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 cost-effective 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 CO2 systems 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 as summarized in the table below.
Table 1: Packaged Refrigeration System Code Change Summary
|Freezer Systems (Sizing)
|Cooler/Dock Systems (Sizing)
|All Systems Types (Specific Efficiency)
|75 Btuh/Watt (Ammonia)
|All Systems Types (Specific Efficiency)
|65 Btuh/Watt (Halocarbon)
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. After an extensive market study of costs and efficiency of evaporators, only units with efficiencies in the top 60th percentile would be allowed (i.e., 40 percent of current products would not be not compliant). The proposed thresholds are summarized below.
Table 2: Evaporator Specific Efficiency Proposed Thresholds
|Liquid Feed Type
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
Measure proposals, supporting documents, and other outside references will be made public as they become available.
- CASE Study Results Report – Nonresidential Refrigeration System Opportunities
- Final CASE Report – Nonresidential Refrigeration System Opportunities
- Draft CASE Report – Nonresidential Refrigeration System Opportunities
Round Two Utility-Sponsored Stakeholder Meeting Materials
- Notes – April 2 – Refrigeration System Opportunities
- Agenda – April 2 – Refrigeration System Opportunities
- Presentation – April 2 – Refrigeration System Opportunities
- Submeasure Summaries – Refrigeration System Opportunities
Round One Utility-Sponsored Stakeholder Meeting Materials
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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