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Single Family Variable Capacity HVAC Compliance Software Revisions

Measure Description

This measure will improve compliance modeling of duct performance for two-speed or variable speed split system HVAC systems (excluding mini- and multi-split systems) unless ducts are located inside conditioned space, or if systems utilize qualified zone controls. Variable capacity split system air conditioners and heat pumps typically have significantly higher SEER and EER ratings than single speed equipment.  Current compliance calculations allow full credit for the higher ratings, yet research conducted by the UC Davis Western Cooling Efficiency Center (WCEC) has shown that reduced air velocity in ducting significantly degrades cooling performance when ducts are in hot attics. “Qualified zone controls” are those that modulate compressor and fan speed based on the number of zones calling.  As proposed, modifications to CBECC-Res will account for reduced distribution airflow and will be calibrated and verified using the WCEC’s laboratory test data and simulation model.

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

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Draft CASE Report Now Available (Comments accepted until June 19, 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.

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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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