Specifications
2008 Residential Appendices RA3-15
Appendix RA3 – Residential Field Verification and Diagnostic Test Protocols
check the measurements as many times as necessary to pass the test. After the final adjustment has
been made, allow the system to run 15 minutes before completing the final measurement procedure.
6. For the Installer, if the difference is between minus 3°F and minus 100°F, then the system does not
pass the required refrigerant charge criterion, the Installer shall add refrigerant. Adjust refrigerant
charge and check the measurements as many times as necessary to pass the test. After the final
adjustment has been made, allow the system to run 15 minutes before completing the final
measurement procedure.
7. Calculate Actual Superheat as the suction line temperature minus the evaporator saturation
temperature. Actual Superheat = T
suction, – Tevaporator, sat.
8. If possible, determine the Superheat Range specified by the manufacturer.
9. In order to allow for inevitable differences in measurements, the Pass/Fail criteria are different for the
Installer and the HERS Rater.
For the Installer, if the superheat is within the manufacturer’s superheat range, then the system passes
the metering device criterion. If the manufacturer’s specification is not available and the superheat is
between 4°F and 25°F, then the system passes the metering device criterion.
For the HERS Rater inspecting the system, if the superheat is between 3°F and 26°F, then the system
passes the metering device criterion.
RA3.2.2.7 Minimum Airflow
In order to have a valid c
harge test, the airflow shall be verified by passing the temperature split test.
Alternatively, one of the three measurements in RA3.3 may be used with a measured airflow in excess of 300
cfm/ton. The temperature split test method is designed to provide an efficient check to see if airflow is above
the required minimum for a valid refrigerant charge test. The following steps describe the calculations using the
measurement procedure described in Section RA3.2.2.5. If a system fails, then remedial actions must be taken.
If the airflow is changed and the refrigerant charge has previously been tested, then the refrigerant charge shall
be re-tested. Be sure to run the air conditioner for 15 minutes after the final adjustments before taking any
measurements. Both the airflow and charge must be re-tested until they simultaneously pass.
1. Calculate the Actual Temperature Split as the return air dry-bulb temperature minus the supply air dry-
bulb temperature. Actual Temperature Split = T
return, db - Tsupply, db
2. Determine the Target Temperature Split from Table RA3.2-3 using the return air wet-bulb temperature
(T
return, wb) and return air dry-bulb temperature (Treturn, db).
3. If a dash mark is read from Table RA3.2-3 then there probably was an error in the measurements
because the conditions in this part of the table would be extremely unusual. If this happens, re-
measure the temperatures. If re-measurement results in a dash mark, complete one of the alternate
airflow measurements in Section RA3.3.
4. Calculate the difference between target and actual temperature split (Actual Temperature Split-Target
Temperature Split).
5. In order to allow for inevitable differences in measurements, the Pass/Fail criteria are different for the
Installer and the HERS Rater.
For the Installer,
a) If the difference is between plus 3°F and minus 3°F, then the system passes the adequate airflow
criterion.
b) If the difference is greater than plus 3°F, then the system does not pass the adequate airflow criteria
and the airflow shall be increased by the installer. Increasing airflow can be accomplished by
eliminating restrictions in the duct system, increasing blower speed, cleaning filters, or opening
registers. After corrective measures are taken, repeat the measurement procedure as often as
necessary to establish adequate airflow. After the final adjustment, allow the system to stabilize for 15
minutes before taking the final measurements.