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