How Many Heads Can a Mini-Split Have, and Does Adding One Trigger Title 24?
Title 24 sets no maximum number of indoor heads. The practical limit comes from the load calculation and from the combinations the manufacturer has rated. Adding a head to a running system brings a new coil, metering device and piping, so plan on the refrigerant charge check applying again and confirm with the building department.
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Where a head limit would come from
The Energy Standards contain no indoor-unit cap. Two other things set the ceiling. The first is the load calculation: heating and cooling loads are worked out with ACCA Manual J, the SMACNA residential manual or the ASHRAE Handbook method (Section 150.0(h)1), and the equipment must meet them (Section 150.0(h)5). The second is the maker: efficiency is checked against the Energy Commission's certified-appliance database (Sections 110.1 and 110.2), so ask which indoor-unit combinations are rated for your outdoor unit.
Sizing a multi-zone system for an addition
When the heads serve a new room, the total load of all rooms on the equipment, called a block load, may be used for sizing (Exception 1 to Section 150.0(h)1). Ductless systems are also excepted from the maximum-capacity tables that govern additions (Exception 1 to Section 150.2(a)1Eii). The load calculation page shows what the plan checker expects.
Adding one head to a system that already runs
A new head brings an evaporator coil, a refrigerant metering device and more piping. Section 150.2(b)1F treats installing those parts as altering the system, and its heat pump sentence names minisplit systems, so treat the charge check as applying again. Most mini-splits use the weigh-in route. The short line-set adjustment is written for a new factory-charged outdoor unit (RA3.2.3.1.1.1); with the old outdoor unit staying, the option left is to recover, evacuate and weigh in the whole charge (RA3.2.3.1.1.2). A cooling-only system in some zones escapes the field test, as the cooling-only comparison explains.
A head can change what a room is
Mechanical heating above 10 Btu per hour per square foot, or cooling above 5, makes a space directly conditioned (Section 100.1). A head placed in a garage or porch can create newly conditioned space; see the garage and workshop page.
Who handles the refrigerant
Only an EPA-certified technician may add or remove refrigerant, and the ECC-Rater may not. The installation checklist walks through one complete job, and the addition design guide covers a new room. Reports start on our residential reports page.
Common Title 24 Questions
- When is Title 24 required for a home?
- Does a remodel need Title 24?
- Does a room addition need Title 24?
- What plans are needed for a residential Title 24 report?
- How much does a residential Title 24 report cost?
- How long does a residential Title 24 report take?
Frequently Asked Questions
Not in Title 24. The limit is the manufacturer's rated combinations and the room-by-room load calculation, so check the equipment submittal before you design the layout.
The building department decides what needs a permit. Ask before buying, because an added head can bring the refrigerant charge verification and, in a garage or porch, the addition rules.
Explore Mini-Splits
- Installing a Mini-Split Yourself: What Title 24 Still Requires
- Mini-Split in a Garage, Shed or Workshop: Does It Trigger Title 24?
- Mini-Split Installation Title 24 Checklist
- Refrigerant Line Set Insulation on an AC or Mini-Split: What the Code Requires
- Replacing Ducted Central Air With Mini-Splits: What Title 24 Asks
View all Mini-Splits guides → · HVAC and Water Heating · Title 24 guide