Refrigerant charging is required for all split systems and may be required over the life cycle of all DX or HP equipment. Charging must only be completed by technicians who have an EPA Type II or Universal certification. These requirements are in addition to and do not supersede any local code or project documentation requirements. It is the installer's responsibility to ensure that all work meets the project specification and local code requirements.
AboveAir Technologies utilizes R-410A refrigerant in its units. R-410A is a blended refrigerant (a near azeotropic of R-32 and R-125) formulated as a non-ozone depleting replacement for R-22 in residential and commercial air conditioners and heat pumps. R-410A exhibits higher operating pressures and refrigerant capacity than R-22 and cannot be used as a direct substitution for R-22 in existing systems.
Do not attempt to charge the system prior to completion of installation. All interlocking wiring, refrigerant piping, condenser piping, ductwork, and control sensors must be installed for proper system charging. Do not attempt to charge until initial air and water or glycol balancing has been completed. Do not attempt to charge systems at conditions where they would not normally operate.
After completing all system piping connections and prior to introducing any refrigerant in to the system, pressurize the system to 150 psig with dry nitrogen. Once the system has been pressurized, monitor the pressure to verify that there are no leaks in the system.
In order to dehydrate the system, a high vacuum pump must be used to pull vacuum. Draw a vacuum of at least 500 microns and hold the vacuum for at least 2 hours. Proper system evacuation is essential to ensure compressor life; improper evacuation may result in moisture being left in the system and reduced system life.
To break vacuum on the system, supply liquid R-410A to the liquid line or receiver port. For split systems, a starting refrigerant charge is typically noted in the mechanical section or shipped with a charge in the condensing section (refer to condenser section labeling). You will need to add additional charge for line sets longer than indicated. If recharging a packaged system, the system charge will be noted on the unit’s name plate. Weigh in the initial charge. The majority of the system’s charge should readily be dispensed to the system at this point if a proper vacuum was achieved.
Turn the system on. Offset sensors or set points as necessary to operate the compressor continuously while charging the system. Refer to the controller or thermostat manual for more information.
Add refrigerant to allow the discharge pressure to rise to 325-420 psig. Note that equipment with flooded head pressure control valves will need to exceed 300 psig in order for the head pressure valve to fully open.
Measure the liquid subcooling near the outlet of the condenser and superheat near the TXV sensing bulb. System should be charged to approximately 8-20°F subcooling with a tolerance of ±3°F (systems with receivers will typically be on the low side). System superheat should be approximately 12-15°F and must not exceed 20°F. Continue to add liquid refrigerant as necessary to meet adequate subcooling requirements.
If the unit is equipped with hot gas reheat, the unit’s charge must be checked with the hot gas reheat valve open. After completing the initial charging procedure and allowing the unit to settle, open the hot gas reheat valve by offsetting set points/sensor readings or manually through the micro-controller. Adjust system charge if necessary.
If the unit is a heat pump, switch the unit from cooling to heating operation and verify the unit switches to heat pump operation. Depending on the season, it may be possible to run the system in its heat pump. Verify that system pressures and temperatures are acceptable if this is case. Under high ambient conditions, running in the heat pump mode for any length of time is strongly discouraged and pressures should be re-checked for heat pump operation during the heating season.