Nonresidential HVAC Economizer ModificationsHVAC
The 2013 Title 24 prescriptively requires that economizers be installed on cooling fan systems with cooling capacity equal to or greater than 54,000 Btu/h. A mandatory control requirement for economizers on air-cooled unitary direct expansion systems is a Fault Detection and Diagnostic (FDD) system that meets a list of requirements in section 120.2(i). Manufacturers certify these FDD systems to the CEC, and the CEC lists the FDD systems online.1 In response to stakeholder concerns a set of modifications and additions to the 2013 code are proposed:
- Clarify in mandatory Section 120.2(f) that outdoor air supply and exhaust dampers shall open with fan operation only during a pre-occupancy purge cycle, occupied periods, or when economizing conditions are favorable.
- Clarify in mandatory Section 120.2(i) that controls for the economizer FDD can be either stand-alone or integrated with the system controller.
- Delete refrigerant pressure sensor requirements for economizer FDD in mandatory Section 120.2(i)3 and refrigerant diagnostics requirements in NA7.5.11.
- Clarify that heating-related requirements for economizer FDD in mandatory Section 120.2(i)5 and 6 are only applicable for systems that have heating capabilities.
- Clarify in mandatory Section 120.2(i)7 how faults are reported.
- Modify prescriptive Section 140.4(e) and Appendix NA7.5.4 to specify economizer and return air damper open and closed positions, rather than percent of design airflow.
- Modify prescriptive Section 140.4(e) and Appendix NA7.5.4 to require damper leakage testing be certified to the CEC.
- Clarify prescriptive Section 140.4(e) to require damper reliability for 60,000 damper opening and closing cycles.
- Integrate the Economizer FDD Testing document and System Declaration into the Joint Appendices.2
The proposed measures do not expand the scope of the Standards, but rather modify and clarify existing code language. In addition to clarifying 2013 code language, the Statewide CASE Team developed a list of longer term code changes and associated research needs necessary for the 2019 Title 24 update cycle.
The Statewide CASE Team worked closely with the WHPA, an advisory group comprised of manufacturers, consultants, researchers, distributors, and contractors, to ensure that industry perspectives were understood. The WHPA was created by the California Utilities and California Public Utilities Commission.
 Currently available at: http://www.energy.ca.gov/title24/equipment_cert/fdd/FDD_Certification_Guidance.pdf
Several stakeholder meetings and CEC staff workshops were held regarding the Nonresidential HVAC Economizer Modifications building energy efficiency topic. The list of past meetings and hearings can be found here. If you would like to receive email updates on this CASE topic, click the link below.