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Checking Refrigerant Charge (cont�)
With an accurate scale (+/– 1 oz. [28.3 g]) or
volumetric charging device, adjust charge
difference between that shown on the unit data
plate and that calculated for the new system
installation� If the entire system has been
evacuated, add the total calculated charge�
IMPORTANT:
not always accurate since the application can
affect the optimum refrigerant charge� Charging by
weight is considered a starting point ONLY� Always
check the charge by using the Charging Chart
and adjust as necessary� CHARGING BY LIQUID
SUBCOOLING MUST BE USED FOR FINAL
CHARGE ADJUSTMENT�
With thermostat in the "Off" position, turn on
the power to the furnace or air handler and the
condensing unit� Start the condensing unit and the
furnace or air handler with the thermostat� Verify
that the outdoor unit is operating and the indoor
air mover is delivering the correct airflow for the
system size�
Gross Charging by Pressures
1� Following airflow verification and charge weigh-
in, run the unit for a minimum of 15 minutes
prior to noting pressures and temperature�
IMPORTANT:
as measured at the indoor coil must be within
2°F [1.1°C] of the following during gross charge
(pressure) evaluation:
Cooling Mode: 80°F [26.7°C] Dry Bulb
Heating Mode: 70°F [21.1°C] Dry Bulb
NOTICE:
If the Indoor temperature is above
or below this range, run the system to bring the
temperature down or run the electric heat/furnace
to bring the temperature within this range� System
pressure values provided in the Charging Chart for
outdoor dry bulbs corresponding to conditions outside
of these ranges are provided as reference ONLY�
26
Charging by weight is
Indoor conditions
2� Note the Outdoor Dry Bulb Temperature,
ODDB° = _____°F [_____°C]� Unit charging is
recommended under the following outdoor
conditions ONLY:
Cooling Mode ONLY: 55°F [12.8°C] outdoor dry
bulb and above
3� Locate and note the design pressures� The
correct liquid and vapor pressures are found at
the intersection of the installed system and the
outdoor ambient temperature on the Charging
Chart located inside the access panel cover�
Liquid Pressure: = ______psig; Vapor Pressure =
______psig
NOTICE:
The refrigerant pressures provided
are for gross charge check ONLY� These pressure
values are typical, but may vary due to application�
Evaporator load (indoor coil in cooling mode/outdoor
coil in heating mode) will cause pressures to deviate�
Note that all systems have unique pressure curves�
The variation in the slope and value is determined
by the component selection for that indoor/outdoor
matched system� The variation from system to
system seen in the table is normal� The values listed
are for the applicable indoor coil match ONLY!
4� If the measured liquid pressure is below the
listed requirement for the given outdoor and
indoor conditions, add charge� If the measured
liquid pressure is above the listed requirement
for the given outdoor and indoor conditions,
remove charge�
Final Charge by Subcooling
1� After gross charging, note the designed
subcooling value� The correct subcooling value
is found at the intersection of the installed
system and the outdoor ambient temperature
on the Charging Chart located inside the access
panel cover�
SC° from Charging Chart = _____°F [_____°C].
IMPORTANT:
measured at the indoor coil are required to be
between 70°F [21.1°C] and 80°F [26.7°C] dry
bulb for fine-tuned unit charge adjustment� Unit
charging is recommended under the following
outdoor conditions ONLY:
Cooling Mode ONLY: 55°F [12.8°C] outdoor dry
bulb and above
Indoor conditions as
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