Reznor JT4BD Unit Installation Manual - Manual (Page 18)

18
T4BD HeaT MoDe VeRiFiCaTion CHaRTS - HeaTing 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 (Tables
10 - 16, pages 19 - 21), 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. 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.
application notes on the use of Heating-mode charge verification charts:
notES:
1. All pressures are listed psig and all temperatures in °F
2. Discharge temperatures greater than charted values
indicate an undercharged system .
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
.
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 (Figure 2 page 5), then
it is not possible to measure the liquid pressure. to
approximate the liquid pressure, subtract 7 psig from
the discharge pressure.