(a) The procedures in Appendix RA3.2 are for use for residential air-cooled air conditioners and air-source heat pumps to verify the systems have the required refrigerant charge.
(b) For dwelling units with multiple air conditioners or heat pumps, the procedures shall be applied to each system separately.
(c) Appendix RA3.2 defines two procedures, the Standard Charge Verification Procedure in Section RA3.2.2 and the Weigh-in Charging procedure in Section RA3.2.3
(d) Failure to follow the manufacturer’s installation and charging instructions may result in significant refrigeration system faults that may invalidate refrigerant charge and metering device verification results. The installer shall certify that he/she has conformed to the manufacturer’s instructions and specifications for charging the system prior to proceeding with the verification procedures in this appendix.
RA3.2.1.1 Scope of the Standard Charge Verification Procedure (RA3.2.2)
(a) 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.
(b) 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 as specified in Section RA3.2.2.7.
(c) The procedures in Section RA3.2.2 require verification (for applicable systems) that the metering device is operating properly.
(d) The procedures in Section RA3.2.2 may be used when the outdoor air temperature is 55°F or above.
(e) 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.
(f) 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.
(g) When the procedures in Section RA3.2.2.7.3 (alternative to compliance with minimum system airflow) are utilized for compliance, HERS verification compliance shall not use group sampling.
RA3.2.1.2 Scope of the Weigh-In Charging Procedure (RA3.2.3)
(a) The procedures in Section RA3.2.3 are applicable to air-cooled air conditioners or air-source heat pumps.
(b) The weigh-in charging procedure is an acceptable method for demonstrating compliance at any outdoor temperature.
(c) Use of the Section RA3.2.3 procedure does not exempt the system from compliance with all applicable minimum airflow verification requirements.
(d) When the procedures in Section RA3.2.3 are utilized by the HVAC installer, HERS verification compliance shall not use group sampling.
(e) 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 Special Case Refrigerant Charge Verification Protocol in Reference Residential Appendix RA1.
(f) 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 special case refrigerant charge verification protocol in Reference Residential Appendix RA1 available for use with the system for outdoor temperatures below 55°F.
(g) 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 special case refrigerant charge verification protocol in Reference Residential Appendix RA1 available for use with the system.
(h) The procedures in Section RA3.2.3.1 shall not be utilized by HERS Raters for verification of refrigerant charge.
(i) 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 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.
This section specifies the standard charge verification procedure. Under this procedure, the refrigerant charge is verified using the "superheat charging method" for systems with fixed metering devices, or the "subcooling charging method" for systems with thermostatic expansion valves (TXV) or electronic expansion valves (EXV).
The following sections describe the required instrumentation; required calibration for the instrumentation; required diagnostic measurements; and the required calculations to determine results that must be compared to the criteria in Table RA3.2-1 to determine compliance.
Refrigerant charge verification utilizing the procedures in Section RA3.2.2 compliance with a minimum airflow rate across the cooling coil at the time of charge verification, as defined in RA3.2.2.7.
Table RA3.2-1 summarizes the standard charge verification protocols and defines the corresponding compliance criteria that shall be used by system installers and HERS Raters.
|
Case |
User Application |
Compliance Criteria
|
Procedure(s) |
|
Standard Charge Verification Procedure - Fixed Metering Device Systems |
Installer Testing at Final |
55°F ≤ Outdoor Air Dry-bulb Temp ≤ 115°F
Return Air Dry-bulb Temp ≥ 70°F
Return Air Wet-bulb Temp ≤ 76°F
Superheat tolerance ±5°F of the specified target |
|
|
Standard Charge Verification Procedure - Fixed Metering Device Systems |
HERS Rater Testing |
55°F ≤ Outdoor Air Dry-bulb Temp ≤ 115°F
Return Air Dry-bulb Temp ≥ 70°F
Return Air Wet-bulb Temp ≤ 76°F
Superheat tolerance ±8°F of the specified target |
|
|
Standard Charge Verification Procedure - Variable Metering Device Systems |
Installer Testing at Final |
55°F ≤ Outdoor Air Dry-bulb Temp ≤ 120°F
Return Air Dry-bulb Temp ≥ 70°F
Subcooling tolerance ±3°F of the manufacturer-specified target1
Metering Device tolerance: Superheat meets the Manufacturer's specifications or 4°F ≤ Superheat ≤ 25°F |
|
|
Standard Charge Verification Procedure - Variable Metering Device Systems |
HERS Rater Testing |
55°F ≤ Outdoor Air Dry-bulb Temp ≤ 120°F
Return Air Dry-bulb Temp ≥ 70°F
Subcooling tolerance ±6°F of the manufacturer-specified target1 and Subcooling ≥2°F
Metering Device tolerance: Superheat meets the Manufacturer's specifications or 3°F ≤ Superheat ≤ 26°F |
|
|
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 shall be completed 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.
RA3.2.2.1 Minimum Qualifications for this Procedure
Persons who use this procedure to demonstrate compliance with Title 24 Part 6 shall be qualified to perform the following:
(a) Obtain accurate system pressure and saturation temperature readings utilizing digital refrigeration gauges.
(b) Obtain accurate temperature readings utilizing a digital thermometer and temperature sensors.
(c) Check calibration of digital refrigerant gauges using a known reference pressure.
(d) Check calibration of digital thermometer and temperature sensors using a known reference temperature.
(e) Determine the required or best location for temperature measurements in duct systems and on refrigerant lines.
(f) Calculate the measured superheat and subcooling.
(g) Determine the required superheat, based on the conditions present at the time of the test.
(h) Determine if measured values are accurate.
RA3.2.2.2 Instrumentation Specifications
Instrumentation for the procedures described in this section shall conform to the following specifications:
Temperature measurements shall be made utilizing digital temperature measurement instrumentation (combined sensor plus device for data acquisition, processing and reporting) that shall have dual channel capability in Celsius or Fahrenheit and conform to the following specifications: