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applicaTion noTeS For uSing T4QD HeaT moDe
legenD
Shaded boxes indicate flooded conditions.
Rated design values. Suction pressure will
vary from design value if outdoor air flow,
entering dry bulb, or entering wet bulb
temperatures vary .
• read all notes and warnings for the cooling-mode charging charts and tables prior to using the heat
mode verification tables. 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.
• When repairing system leaks, always use a nitrogen (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.
• Before using Tables 7 - 12 (pages 14-15), determine the outdoor ambient temperature and the return air temperature
to the unit. Locate the appropriate location on the units verification chart based on those measurements to determine
the ideal liquid line pressure and temperature. Verify the outdoor fan and compressor are running and the outdoor
coil is free from frost accumulation. Also verify the system is not operating in defrost mode before inspecting the
system.
• Always use quality instruments that are in good working order to measure the actual operating point of the
refrigeration system. The liquid line temperature should be within 2 degrees of the ideal value and the pressure
should be within 2%.
• The most reliable way of verifying the system is at the correct charge is to evacuate the system and weigh in the
charge to the amount shown on the rating label. However, if an inspection with these verification tables does not
line up with the values shown and the ambient temperature is above 50˚ F, then a more accurate way to inspect
the system for proper charge is with charging charts and tables in the cooling mode section. Switch the unit into
cooling mode and allow it to operate and stabilize for a few minutes then inspect the unit operation with the cooling
mode charts and procedures.
before changing the unit charge, always inspect the following items first:
1. Inspect the liquid line temperature on the inlet and outlet of the filter dryers. If it is the factory dryer and in good
condition there should be no temperature difference. If the temperature difference is larger than 5˚, replace the filter
dryer with one that is bi-directional and has acid removal capability. Refer to the unit RPL for the recommended
part number and size.
2. Inspect the units input voltage. Units operating at less than 95% of the nominal voltage may deviate more from the
chart then previously stated.
3. Inspect the input voltage for a phase imbalance. Units with greater then a 2% disparity will not operate at the rated
performance.
4. Verify that the unit filters are installed and are clean. The pressure drop across the filters should not exceed 0.08
in-W.C.
5. Inspect the indoor coil, indoor blower and blower motor for cleanliness, clogging, and proper operation. Verify the
drive belt is in good condition and properly tightened.
6. Inspect the system for leaks. If any leaks are detected, repair them immediately. Re-inspect the return air and
ambient temperatures and verify that the correct system point on the verification chart was selected.
Do noT use the tables in systems that have the fan cycling under a low-ambient control. Low-ambient controls are
for cooling operation. In heating mode, the low ambient control should be disabled. Unless the unit is in defrost mode,
the outdoor fan should always operate in conjunction with the compressor.
VERiFiCATiOn TABLES - HEATing OnLy
noTeS:
1. All pressures are listed psig and all temperatures in °F
2. Discharge temperatures greater than charted values
indicate an undercharged system .
13
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