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Application Notes on the use of Heating-mode charge verification charts:
DO NOT use these charts for two stage systems operating only under a single stage call for heating. (Or for
units with an electric heat kit installed, that they are not operating on a 3rd stage call for heat.)
DO NOT utilize the charts in systems that do not have all the outdoor fans energized, or have the fans 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 fans should always operate in
conjunction with the compressors.
Read all notes and warnings for the Cooling-mode
charging charts prior to utilizing these Heating-mode
charge verification charts.
All Q6SP-090/120 units are shipped from the factory with
accumulators installed in the refrigeration systems and
the correct factory charge. The charge verification charts
Figure 15
&
Figure 16 (page 29)
reference when the unit is in heating-mode and allow the
inspection of the liquid line pressures and temperature
for both stage one and stage two. In heating mode, stage
one and two will operate at similar but slightly different
operating points.
Before using these charts, determine the Outdoor ambient
temperature and the Return air temperature to the unit.
(If the unit is equipped with an economizer, determine the
mixed air temperature entering the filters.)
Locate the appropriate location on the units verification
chart based on those measurements to determine the
ideal liquid line pressure and temperature. Ensure that
all outdoor fans are operating, that both compressors are
running and that the outdoor coils are free from any frost
accumulation. Additionally, ensure that 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%. For a more accurate comparison to
the chart, record both the stage one and stage two readings
and compare them to each other. If the system pressures
are with in 8 psig of each other and the temperatures are
with 1.5˚ F then average the values together and compare
them to the chart values.
The most reliable way of ensuring that 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 charts
does not line up with the values shown and the ambient
temperature is above 40˚ F, then a more accurate way to
inspect the system for proper charge is with the cooling
28
Heating Mode, Charge Verification Charts
are provided for quick
mode charging charts. 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 ΔT 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 a leak cannot be located
and stage one and two are operating with similar
characteristics and both stages are sub-cooled, the
system charge is probably correct. Re-inspect the return
air and ambient temperatures and verify that the correct
system point on the verification chart was selected.
Always use safe and environmentally sound methods for
refrigerant handling. When repairing system leakages,
always utilize 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.
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