ADU Refrigerant Charge Verification: When Is It Required?
It depends on the ADU and the equipment. A heat pump in a new detached ADU is verified in every climate zone, an air conditioner only in zones 2 and 8 to 15, and replaced refrigerant parts in a converted room bring the same split. An addition reusing existing equipment is exempt.
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Match the ADU to a trigger
- New detached ADU. Section 150.1(c)7A applies. The compliance manual reads Table 150.1-A as requiring verification for heat pumps in all 16 zones and for air conditioners in zones 2 and 8 to 15.
- Addition with its own new system. A new system serving an attached ADU or garage conversion follows the new-home rule. Extending existing equipment into the addition does not trigger it, under Exception 3 to Section 150.2(a).
- Alteration of a converted room. Replacing a compressor, coil, metering device or refrigerant piping falls under Section 150.2(b)1F: the same zone split, a setback thermostat and 300 cfm per ton of airflow.
The test the ECC-Rater runs
The standard procedure needs outdoor air at 55 F or warmer and compares measured superheat (fixed orifice) or subcooling (expansion valve) with a target. A heat pump is tested in cooling mode. The rater's tolerance is wider than the installer's: 8 F against 5 F on superheat, 6 F against 3 F on subcooling. Airflow is confirmed in the same visit (see ADU airflow verification).
Ductless units and cold days
Many mini-splits cannot take the standard procedure. The installer then weighs in the charge from the manufacturer's coil and line set adjustments while the ECC-Rater watches. Only a certified technician may add or remove refrigerant, never the rater. A factory-charged package unit is the exemption: the installer certifies it was not altered, and the rater does not verify its charge, though airflow is still checked.
If the system fails
The installer corrects the charge and the rater tests again, with every result registered. The failed test page explains the registry rules.
What to hand the rater
- Measurement access holes on the system, unless it cannot take them.
- The installer's CF2R-MCH-25-H, certifying the manufacturer's charging instructions were followed.
- For a weigh-in, the line set length and diameter, the coil size and the refrigerant weights marked at the nameplate.
Each system is verified on its own. See the refrigerant charge page, mini-split options and the ECC-Rater preparation guide, or start on the ADU page.
Common Title 24 Questions
- Do ADUs need Title 24 in California?
- What plans are needed for an ADU Title 24 report?
- How much does an ADU Title 24 report cost?
- How long does an ADU Title 24 report take?
- Does a garage conversion ADU need Title 24?
- Does a JADU need a Title 24 report?
Frequently Asked Questions
Yes, when the project triggers the rule, because heat pump charge is verified in all climate zones. Many ductless units cannot take the standard test, so the usual route is an installer weigh-in that the ECC-Rater observes.
No. The compliance manual says only an EPA-certified technician may add or remove refrigerant, and ECC-Raters may not do so on systems they are verifying.
Explore ADU and JADU
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- ADU Solar Exceptions and Exemptions Under the 2025 Energy Code
- Does an ADU Need Solar Under Title 24?
- What If Plan Check Returns Title 24 Corrections on an ADU?
View all ADU and JADU guides → · Permits and Compliance · Title 24 guide