Mini-Split and Multi-Split HVAC Systems

Mini-split systems are heating and cooling systems that allow you to control the temperatures in individual rooms or spaces. Mini-split systems have two main components, an outdoor compressor and condensing unit, and an indoor air-handling unit (evaporator).

There are different configurations of mini-splits available:

• Single indoor unit mini-split systems, also called single-split systems, have one outdoor unit and a single indoor unit.

• Multi-head mini-split systems have one outdoor unit that serves two or more indoor units connected with a single refrigeration circuit and operate in unison in response to a single indoor thermostat.

• Multiple-split or multi-split systems have one outdoor unit and two or more indoor units connected with a single refrigeration circuit that operate independently in response to at least two indoor thermostats.

Variable-capacity heat pump (VCHP) systems are cooling and heating systems with outdoor units consisting of multiple compressors or a single variable-capacity compressor. Both mini-split and multi-split systems can be VCHP systems.

Title 24 Credit for Mini-Split and Multi-Split HVAC Systems

Is there a performance compliance credit available for installation of a minisplit or multi-split system that does not have more than one compressor or a variable-capacity compressor?

Yes. Mini-split and multi-split single-speed systems may receive credit for having ducts entirely within conditioned space. HERS verification is required to verify that the location of the heads are completely within conditioned space.

Is there performance compliance credit available for installation of a VCHP minisplit or multi-split system?

Yes. VCHP mini-split and multisplit systems may qualify for a 5 percent cooling credit, a 12 percent heating credit, or both, when the performance method of compliance is used. HERS 4 verification is required to confirm:

• Location of the indoor units and ducts are entirely within conditioned space

• Refrigerant charge

• Airflow to all habitable spaces either by use of a ductless indoor unit located in the room, or by use of ducts connected directly to the supply air outlet of a ducted indoor unit

• Zones greater than 150 square feet have a wall-mounted thermostat

Is there a performance compliance credit available for installation of a ducted mini-split or multi-split system?

Yes. Ducted VCHP mini-split and multi-split systems can receive the same heating and cooling efficiency credits as non-ducted VCHP systems. However, if the ducted indoor unit operates continuously by default, the credit will be lower than the credit given to ductless systems due to the additional fan power used by continuous fan operation in ducted systems. (Ductless systems do not have a fan energy penalty for continuous fan operation.) To receive the heating and cooling credits, ducted systems must be certified to the CEC by the manufacturer to be a low-static VCHP system. Note that certification to the CEC is in addition to the AHRI listing. To receive the VCHP credit, HERS verification is required for the items listed under non-ducted systems and the following additional items:

• Low leakage ducts located entirely inside conditioned space

• Minimum airflow rate (350 cfm/ton)

• Air filter sizing

• Air filter maximum pressure drop

Is there performance compliance credit available for ducted systems that do not operate continuously by default?

Yes. Ducted systems can receive a performance credit for reduced fan energy if the system does not operate continuously by default. To receive the credit, the manufacturer must include the non-continuous fan feature in the certification to the CEC. Certification of non-continuous fan operation is not required, but performance credit cannot be used when it is not certified. HERS verification of the fan operation is required to receive the credit. The credit for non-continuous fan operation is not available for non-ducted systems.

Information on the requirements for eligibility, verification, and how to certify ducted low-static systems to the CEC can be found on the Ducted VCHP Certification webpage.

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References

• California Energy Commission Blueprint Issue 132