507607-03
Issue 1827
Page 12 of 23
Table 4. Refrigerant Charge Adjustment
Liquid Line Set Diameter
Oz. Per 5 ft. Adjust from 15
ft. Line Set*
3/8 in.
3 oz. per 5 ft.
* If line length is greater than 15 ft. , add this amount. If line
length is less than 15 ft., remove this amount.
Mineral oils are not compatible with R-410A. If oil must
be added, it must be a polyolester oil.
IMPORTANT
If the system is void of refrigerant, clean the system using
the procedure described below.
1. Use dry nitrogen to pressurize the system and check
for leaks. Repair leaks, if possible.
2. Evacuate the system to remove as much of the
moisture as possible.
3. Use dry nitrogen to break the vacuum.
4. Evacuate the system again.
5. Weigh the appropriate amount of R-410A refrigerant
(listed on unit nameplate) into the system.
6. Monitor the system to determine the amount of
moisture remaining in the oil. Use a test kit to verify
that the moisture content is within the kit’s dry color
range. It may be necessary to replace the filter drier
several times to achieve the required dryness level. If
system dryness is not verified, the compressor will fail
in the future.
The outdoor unit should be charged during warm weather.
However, applications arise in which charging must occur
in the colder months. The method of charging is determined
by the unit’s refrigerant metering device and the outdoor
ambient temperature.
Measure the liquid line temperature and the outdoor
ambient temperature as outlined below:
1. Connect the manifold gauge set to the service valve
ports as follows:
• Low pressure gauge to suction line service valve
• High pressure gauge to liquid line service valve
2. Close manifold gauge set valves. Connect the center
manifold hose to an upright cylinder of R-410A.
3. If room temperature is below 70°F, set the room
thermostat to call for heat. This will create the
necessary load for properly charging the system in the
cooling cycle.
4. Use a digital thermometer to record the outdoor
ambient temperature.
5.
When the heating demand has been satisfied, switch
the thermostat to cooling mode with a set point of
68°F. When pressures have stabilized, use a digital
thermometer to record the liquid and suction line
temperatures.
6. The outdoor temperature will determine which
charging method to use. Proceed with the appropriate
charging method.
Charge Using Weigh-In Method (Fixed Orifice/TXV
Systems) - Outdoor Temperatures Below 65°F
If the system is void of refrigerant, or if the outdoor ambient
temperature is cool, use the weigh-in method to charge the
unit. Do this after any leaks have been repaired.
1. Recover the refrigerant from the unit.
2. Conduct a leak check, then evacuate as previously
outlined.
3. Weigh in the charge according to the total amount
shown on the unit nameplate.
If weighing facilities are not available or if unit is being
charged during warm weather, use one of the following
procedures.
Charge Using Subcooling Method (Fixed Orifice/TXV
Systems) - Outdoor Temperatures 65°F or Above
If charging a fixed orifice or TXV system when the outdoor
ambient temperature is 65°F or above, the subcooling
method can be used to charge the unit.
1. With the manifold gauge hose still on the liquid
service port and the unit operating stably, use a digital
thermometer to check the liquid line temperature.
For best results, use the same digital thermometer
to check both the outdoor ambient and the liquid line
temperatures.
2. At the same time, record the liquid line pressure
reading.
3. Use the temperature/pressure chart to determine the
saturation temperature for the liquid line pressure
reading.
4. Subtract the liquid line temperature from the saturation
temperature (according to the chart) to determine
subcooling.
5. Compare the subcooling value with those shown on
charge label located on back of control box cover.
Charge Using Approach Method (TXV System) -
Outdoor Temperatures 65°F or Above
The following procedure is intended as a general guide
and is for use on expansion valve systems only. For best
results, indoor temperature should be 70°F to 80°F. Monitor
system pressures while charging.
1. Record outdoor ambient temperature using a digital
thermometer.
