Zoned duct systems must demonstrate compliance by diagnostically testing the installed performance, the return sizing tables do not apply to zoned duct systems. The specific compliance requirements for zoned duct systems will depend on whether it includes a single speed or multi/variable-speed condenser.

Single Speed, Zoned Systems

Ducted zoned systems utilizing a single speed air conditioner must meet the above criteria in every single zone configuration. It is not required to verify combinations of zones operating, only the individual zones. The Rater shall turn on cooling sequentially at each controlling thermostat with the other thermostats set to off in order to demonstrate system airflow and fan watt-draw meet the prescriptive targets in each zone configuration.

Example: For a two zone, zoned duct system, the HERS Rater would have to verify airflow/fan efficacy in (2) configurations: zone 1 only and zone 2 only.

Multiple Speed, Zoned Systems Ducted zoned systems utilizing a multi-speed or variable speed compressors only need to be verified to meet the above 350 CFM per nominal ton and 0.58 Watts per CFM criteria with the compressor on high speed and all zones calling for cooling. Verification of individual zones is not required when a multi-speed compressor is installed.