1. The procedures in Section RA3.2.2 are applicable to ducted split system air-cooled air conditioners and ducted split system air-source heat pumps, and may be applicable to packaged air-cooled air conditioners and packaged air-source heat pumps.
2. The procedures in Section RA3.2.2 require verification of the applicable minimum system airflow rate across the cooling coil when refrigerant charge is verified.
3. The procedures in Section RA3.2.2 require verification (for applicable systems) that the metering device is operating properly.
4. The procedures in Section RA3.2.2 may be used when the outdoor air temperature is 55°F or above.
5. When refrigerant charge verification is required for compliance, the applicable procedures in Section RA3.2.2 shall be used by the HVAC installer after installing a new HVAC system or after altering refrigerant-containing components in an existing HVAC system, and after charging the air conditioner or heat pump system in accordance with the manufacturer's instructions and specifications.
6. The applicable procedures in Section RA3.2.2 shall always be used by the HERS Rater for verification of the system's refrigerant charge when HERS verification is required for compliance unless an applicable alternate procedure is available in Reference Residential Appendix RA1, or the Standards specify the Section RA3.2.3.2 procedure (observation of weigh-in) as mandatory for compliance, or as an available option for compliance and the HVAC installer elects to use the RA3.2.3.2 procedure for HERS verification.
7. When the procedures in Section RA3.3.3.1.5 (alternative to compliance with minimum system airflow) are utilized for compliance, HERS verification compliance shall not use group sampling.

1. The procedures in Section RA3.2.3 are applicable to air-cooled air conditioners or air-source heat pumps.
2. The weigh-in charging procedure is an acceptable method for demonstrating compliance at any outdoor temperature.
3. Use of the Section RA3.2.3 procedure does not exempt the system from compliance with all applicable minimum airflow rate verification requirements.
4. When the procedures in Section RA3.2.3 are utilized by the HVAC installer, HERS verification compliance shall not use group sampling.
5. The procedures in Section RA3.2.3.1 may be used by the HVAC installer as an alternative to the Standard Charge Verification Procedure in RA3.2.2, or as an alternative to any applicable Alternative Refrigerant Charge Verification Protocol in Reference Residential Appendix RA1.
6. The procedures in Section RA3.2.3.1 shall be used by HVAC installers when refrigerant charge verification is required for compliance when the outdoor air temperature is below 55°F, and there is no applicable alternative refrigerant charge verification protocol in Reference Residential Appendix RA1 available for use with the system for outdoor temperatures below 55°F.
7. The procedures in Section RA3.2.3.1 shall be used by HVAC installers when refrigerant charge verification is required for compliance when the standard charge verification procedure in RA3.2.2 is not applicable to the system that must demonstrate compliance, and there is no applicable alternative refrigerant charge verification protocol in Reference Residential Appendix RA1 available for use with the system.
8. The procedures in Section RA3.2.3.1 shall not be utilized by HERS Raters for verification of refrigerant charge.
9. The procedures in Section RA3.2.3.2 shall be utilized by HERS Raters for verification of refrigerant charge only when the Standards specify that the Section RA3.2.3.2 procedure shall be used for HERS verification compliance, otherwise only when the Standards specify the RA3.2.3.2 procedure is an available option, and the HVAC installer elects to use the RA3.2.3.2 procedure for HERS verification compliance.

Note:

1. If a manufacturer-specified subcooling target value is not available or cannot be determined, the Executive Director may provide additional guidance for compliance.

The standard charge verification procedure detailed in this section may be used to demonstrate compliance when the outdoor temperature is within the manufacturer's specified temperature range, or the outdoor temperature is 55°F or higher, after the HVAC installer has installed and charged the system in accordance with the manufacturer’s specifications. The return dry bulb temperature shall be maintained above 70°F during the test.

This procedure does not relieve the installing contractor from any obligation to conform to the manufacturers’ specifications for installation, refrigerant charge, or system operation. This procedure is used to determine compliance with Title 24, Part 6.

Persons who use this procedure to demonstrate compliance with Title 24 Part 6 shall be qualified to perform the following:

1. Obtain accurate system pressure and saturation temperature readings utilizing digital refrigeration gauges.
2. Obtain accurate temperature readings utilizing a digital thermometer and temperature sensors.
3. Check calibration of digital refrigerant gauges using a known reference pressure.
4. Check calibration of digital thermometer and temperature sensors using a known reference temperature.
5. Determine the required or best location for temperature measurements in duct systems and on refrigerant lines.
6. Calculate the measured superheat and subcooling.
7. Determine the required superheat, based on the conditions present at the time of the test.
8. Determine if measured values are accurate.

Instrumentation for the procedures described in this section shall conform to the following specifications:

When required for compliance by Standards Section 150.1(c)7Aia, or when return plenum measurements are necessary for compliance with refrigerant charge verification requirements, a 5/8 inch (16 mm) diameter hole shall be provided as shown in Figure RA3.2-1.

Return plenum temperature measurements shall be taken at the location specified in Figure RA3.2-1 when performing the procedures in RA3.2. The measurement access shall be sealed to prevent leakage after the measurements have been completed.

The hole location shown in Figure RA3.2-1 can be applied to any one of the four sides of the return plenum. The hole location shall be labeled "Title 24 – Return Plenum Measurement Access" in at least 12-point type.

For air-handling units with the return located entirely within conditioned space (such as when an up-flow air handler is mounted on a pedestal in a closet in the dwelling, or when the return grille is an integral part of the air-handling unit), the return plenum measurement access hole is not required, and in this case the return air temperature measurements shall be taken at the return grill when performing the procedures in RA3.2.

Systems that cannot conform to the specifications for the hole location shown in Figure RA3.2-1 shall not be required to have holes as described in Figure RA3.2-1; however if return plenum measurements are required for compliance, an alternate location that provides access for making an accurate return plenum measurement shall be used.

Figure RA3.2-1 Measurement Access Hole

The accuracy of instrumentation shall be maintained using the following procedures. A sticker with the calibration check date shall be affixed to each instrument calibrated.

The following procedure shall be used to obtain measurements necessary to verify the required refrigerant charge.

1. Follow the manufacturer’s directions and adhere to the manufacturer's limitations on indoor ambient air temperature (T_{indoor air}) and outdoor ambient air temperature (T_{outdoor air}) applicable to this procedure. Ensure that the return air dry bulb temperature remains equal to or greater than 70°F prior to and while performing the measurements.
2. Verify that a liquid line filter drier has been installed if required per outdoor condensing unit manufacturer's instructions, and installed with the proper orientation with respect to refrigerant flow, if applicable.
3. Connect the refrigerant gauges to the service ports, taking normal precautions to not introduce air into the system.
4. Attach one pipe temperature sensor to the suction line near the suction line (low side) service valve and attach one pipe temperature sensor to the liquid line near the liquid line (high side) service valve. The sensors should be positioned to make good contact with the surface of the refrigerant line.
5. Attach a temperature sensor to measure the condenser entering air dry-bulb temperature. The sensor shall be placed so that it records the average condenser air entering temperature and is shaded from direct sun.
6. Insert a dry-bulb temperature sensor into the return plenum at the "Title 24 – Return Plenum Measurement Access" detailed in Section RA3.2.2.3.
7. Be sure that all cabinet panels that affect airflow are in place before making measurements. The temperature sensors shall remain attached to the system until the final charge is determined.
8. Operate the air conditioner in cooling mode for 15 minutes to allow the temperatures and pressures to stabilize before taking any measurements. While the system is stabilizing, proceed with setting up the remaining temperature sensors if used.
9. If used, place the cotton wick wet-bulb temperature sensor in distilled water, and ensure it is saturated. Do not get the dry-bulb temperature sensors wet.
10. If the system has a fixed metering device, at 12 minutes, insert a wet-bulb temperature sensor into the return plenum at the "Title 24 – Return Plenum Measurement Access" detailed in Section RA3.2.2.3.
11. If the system has a fixed metering device, after the system has operated for 15 minutes, and when the return plenum wet-bulb temperature has stabilized, using the temperature sensor already in place, measure and record the return (evaporator entering) air wet-bulb temperature (T_{return, wb}).
12. Using the temperature sensor already in place, measure and record the return (evaporator entering) air dry-bulb temperature (T_{return, db}).
13. Using the refrigerant gauge or saturation pressure measurement sensor already attached, measure and record the suction line (low side) pressure, and record the refrigerant saturation temperature corresponding to the measured low side pressure (T_{evaporator, sat}).
14. Using the refrigerant gauge or saturation pressure measurement sensor already attached, measure and record the liquid line (high side) pressure, and record the refrigerant saturation temperature corresponding to the measured high side pressure (T_{condenser, sat}).
15. Using the pipe temperature sensor already in place, measure and record the suction line temperature (T_suction,).
16. Using the pipe temperature sensor already in place, measure and record the liquid line temperature (T_liquid).
17. Using the dry-bulb temperature sensor already in place, measure and record the condenser (entering) air dry-bulb temperature (T_{condenser, db}).

The above measurements shall be used to verify the refrigerant charge as described in following sections.

The following steps describe the calculations to determine if the system meets the required refrigerant charge and metering device function using the measurements determined in Section RA3.2.2.5. If a system fails, then remedial actions must be taken by the HVAC system installer. Be sure to run the air conditioner for 15 minutes after the final adjustments before taking any measurements.

Split system air conditioners are shipped from the factory charged with a standard amount of refrigerant as indicated on the nameplate. The manufacturer-supplied refrigerant charge is expected to be the correct amount for the system based on a standard liquid line length and diameter. It is the responsibility of the HVAC installer to ensure that the charge is correct for each air conditioner and to adjust the charge based on liquid line dimensions that deviate from the manufacturer's standard line specification

When the Standards indicate this procedure is required, or is an option for compliance, the HERS Rater shall coordinate with the HVAC Installer to observe the weigh-in charging procedure.

HERS Rater shall observe and confirm:

1. The system is evacuated to 500 microns or less and, when isolated, rises no more than 300 microns over five minutes.
2. The lineset correction is calculated based on the length and diameter of the lineset, including the liquid line filter drier if required per outdoor condensing unit manufacturer instructions.
3. The indoor coil correction to refrigerant weight is used if it is supplied by the manufacturer.
4. The installer adds or removes the amount of charge calculated for the lineset correction or installs the total charge based on lineset, indoor coil, and standard label charge.

Return Air Wet-Bulb Temperature (°F)
(T return, wb)

Return Air Wet-Bulb Temperature (°F)
(T return, wb)