How Big Can a Replacement AC or Heat Pump Be Under Title 24?
Title 24 puts no floor on cooling capacity and no ceiling on a heat pump when the heating load exceeds the cooling load. In additions, heating-only equipment is capped at the design heating load plus 6 kBtu/h, cooling-only at the design cooling load plus 6, and a heat pump at limits set by its load split, unless airflow is field verified at 350 cfm per ton. Ductless systems in additions are exempt.
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Load first
Section 150.0(h)1 and 2 accept ASHRAE, SMACNA or ACCA Manual J methods. Block loads may size equipment for additions. The manual lets a mechanical engineer, the installing mechanical contractor or another qualified person, such as an energy consultant, prepare the calculation.
Selection under Manual S-2023
- Cooling capacity has no minimum limit.
- Furnaces are sized from Table N2.5.
- Heat pump heating capacity must meet the California Building Code minimum without supplementary heat; Section 150.0(h) sets no maximum, though the addition tables below can.
The caps in Tables 150.2-A and 150.2-B
When airflow is not field verified at 350 cfm per ton or more, a single-speed heating-only system is capped at the design heating load plus 6 kBtu/h and a cooling-only system at the design cooling load plus 6 kBtu/h. A heat pump has no maximum when the heating load exceeds the cooling load. When the cooling load is larger, its cooling is capped at the design cooling load plus 6, and its heating at the design heating load plus 12 unless the cooling load exceeds the heating load by 12 kBtu/h or more. Variable and multi-speed systems also face an 80 percent lowest-speed limit in some cases. Where airflow is verified at 350 cfm per ton, there is no maximum.
Exceptions
For additions, ductless systems are exempt, and a variable- or multi-speed system whose maximum falls between two available sizes may take the larger (Exceptions 1 and 2 to Section 150.2(a)1Eii).
When a replacement reaches the tables
Section 150.2(a)1E speaks to additions. For alterations, Section 150.2(b)1C names Table 150.2-A for entirely new or complete replacement systems, defined as all the equipment, such as condensing unit, coil and air handler, plus an entirely new duct system. The manual's Table 9-12 summarizes the limits for additions and alterations, so ask your report preparer how the job is classified.
See HVAC load calculations, airflow verification and the air conditioner checklist. Reports start at residential Title 24.
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
Yes. Its heating capacity must meet the California Building Code minimum for the load, without counting supplementary heat. Cooling capacity has no minimum limit.
The manual lists a mechanical engineer, the mechanical contractor installing the equipment or another person qualified under Division 3 of the Business and Professions Code, such as an energy consultant.
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