7
Charging the Unit in AC mode
(At outdoor temperatures above 55° F for
optimized sub-cooling of 10° F - 12° F.)
1. With the system operating at steady-state, measure the
liquid refrigerant pressure (in psig) at the outdoor unit
service valve.
2. Measure the liquid refrigerant temperature (in
Fahrenheit) at the service valve.
3. Determine the required liquid refrigerant pressure from
Table 3, (page 10), Table 4, (page 10), Table 5,
(page 11), or Table 6, (page 11).
• IfthepressuremeasuredinStep1isgreaterthan
the required liquid refrigerant pressure determined
in Step 3, then there is too much charge in the
system. Remove refrigerant and repeat Steps 1
through 3 until the system is correctly charged.
• IfthepressuremeasuredinStep1islessthanthe
required liquid refrigerant pressure determined in
Step 3, there is too little charge in the system. Add
refrigerant and repeat Steps 1 through 3 until the
system is correctly charged.
Charging Charts & Application Notes
• This equipment’s cooling system contains
refrigerant under high pressure. Always use safe
and environmentally sound methods when handling
refrigerant handling or servicing the unit. Review
the factory literature and safety warnings prior to
servicing.
• Whenrepairingsystemleaks,alwaysuseanitrogen
(inert) gas to protect the refrigerant system and pressure
check the repair before re-charging. Always replace
the filter-dryers when performing any repair to the
refrigeration system with one capable of acid removal.
After completing the repairs, evacuate the system to
350 - 500 microns and weigh in the refrigerant to the
amount specified on the unit rating label.
• The refrigerant charging charts Figure 2, (page 8),
Figure 3, (page 8), Figure 4, (page 9), & Figure 5,
(page 9) are applicable only to matched assemblies
of NORDYNE equipment and listed airflows for the
indoor coil. NOTE: Before using these charts, make
sure the unit is in a stable operating mode. As shown
in the charts, the ideal system sub-cooling can vary
over the range of operation. Reference the charts to
determine the ideal amount of sub-cooling for a given
liquid pressure. Units charged to other values will not
perform at the rated unit efficiency (EER) or rated
Coefficient of Performance (COP) in heating mode.
• Table 3, (page 10), Table 4, (page 10), Table 5,
(page 11), or Table 6, (page 11) are valid for a
variety of indoor, return air conditions and are most
influenced by the outdoor ambient temperature, outdoor
fan operation and the unit operating voltage. Before
using these tables, make sure the unit is in a stable
operating mode. The ideal system sub-cooling can vary
over the range of operation. Reference the tables to
determine the ideal amount of sub-cooling for a given
liquid pressure. Units charged to other values will not
perform at the rated unit efficiency (EER) or rated
Coefficient of Performance (COP) in heating mode.
• Toinspectasystemsoperationusingqualityinstruments,
match the measured liquid temperature to the units table.
The measured liquid pressure reading should be within
3% of the table value for most installations.
• Forsystemsthatareoperatingwithmorethana5%
deviation, inspect the unit for the proper voltage and
phase balance and the refrigeration system for leaks.
• Unitsthatareoperatingatlessthen95%ofthenominal
voltage or with a 2% phase imbalance may see a more
significant deviation than the amount stated above.
• DO NOT use the charts in systems that have a fan cycling
under low-ambient control. Refer to the low-ambient kit
instructions for more information (If applicable).
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