12
Heat Mode Verification Tables & Application
Notes
(Heat Mode Only)
• Read all notes and warnings for the Cooling-mode
charging charts prior to using these Heating-mode
charge verification charts. 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.
• Heat Mode Verification Tables are provided for quick
reference when the unit is in heating mode and for the
inspection of the liquid line pressures and temperatures.
See
,
• 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 the heat mode verification tables, 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 discharge pressure and temperature.
See
, and
.
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 discharge 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 charts
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 the cooling
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
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.
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 charts 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.
LEGEND
Shaded boxes indicate flooded conditions.
Rated design values. The suction pressure
will vary from design value if outdoor air
flow, entering dry bulb, or entering wet bulb
temperatures vary.
NOTES:
1. All pressures are listed psig and all temperatures in °F
2. Discharge temperatures GREATER than charted values
indicate an UNDERCHARGED system.
3. Discharge temperatures LESS than charted values
indicate an OVERCHARGED system.
