18
Application Notes & Heat Mode Verification Tables (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.
• 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
Table 12 (page 19)
,
Table 13 (page 19)
,
Table 14 (page 19)
,
Table 15
(page 19)
,
Table 16 (page 20)
,
Table 17 (page
20)
, &
Table 18 (page 20)
. 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.
IMPORTANT NOTE:
If the unit is equipped with a liquid valve with an
outdoor restrictor as shown in
Figure 2 (page 4)
,
then it is not possible to measure the liquid pressure.
To approximate the liquid pressure, subtract 7 psig
from the discharge pressure.
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.
1. All pressures are listed in psig and all temperatures in ° F
2. Discharge temperatures greater than charted values indicate an undercharged system.
