SERVICING
27
Liquid
Pressure
Saturated Liquid
Temperature °F
PSIG
R-410A
200
70
210
73
220
76
225
78
235
80
245
83
255
85
265
88
275
90
285
92
295
95
305
97
325
101
355
108
375
112
405
118
SATURATED LIQUID PRESSURE
TEMPERATURE CHART
Two Speed Application (*PH1460)
Run the unit on low stage cooling for 10 minutes until
refrigerant pressures stabilize. Follow the guidelines and
methods below to check unit operation and ensure that the
refrigerant charge is within limits. Charge the unit on low
stage.
1. Purge gauge lines. Connect service gauge manifold
to access fittings. Run system at least 10 minutes to
allow pressure to stabilize.
2. Temporarily install thermometer on liquid (small) line
near liquid line access fitting with adequate contact
and insulate for best possible reading.
3. Check subcooling and superheat. Two stage systems
running on low stage with TXV application should
have a subcooling of 5 to 7 ºF and superheat of 15 to
18ºF.
A. If subcooling and superheat are low, adjust
TXV to 15 to 18ºF superheat, then check
subcooling.
NOTE: To adjust superheat, turn the valve stem
clockwise to increase and counter clockwise to
decrease.
B. If subcooling is low and superheat is high, add
charge to raise subcooling to 5 to 7 ºF then
check superheat.
C. If subcooling and superheat are high, adjust
TXV valve to 15 to 18ºF superheat, then check
subcooling.
D. If subcooling is high and superheat is low, adjust
TXV valve to 15 to 18ºF superheat and remove
charge to lower the subcooling to 5 to 7 ºF.
NOTE: Do NOT adjust the charge based on suction
pressure unless there is a gross undercharge.
4. Disconnect manifold set, installation is complete.
Subcooling = Sat. Liquid Temp. - Liquid Line Temp.
Heat Pump - Heating Cycle
The proper method of charging a heat pump in the heat
mode is by weighing the charge according to the total
charge listed on the rating plate.
Checking Subcooling
Refrigerant liquid is considered subcooled when its
temperature is lower than the saturation temperature
corresponding to its pressure. The degree of subcooling
equals the degrees of temperature decrease below the
saturation temperature at the existing pressure.
1. Attach an accurate thermometer or preferably a
thermocouple type temperature tester to the liquid
line close to the pressure switch.
2. Install a high side pressure gauge on the high side
(liquid) service valve at the front of the unit.
3. Record the gauge pressure and the temperature of
the line.
4. Compare the hi-pressure reading to the "Required
Liquid Line Temperature" chart on the following
page. Find the hi-pressure value on the left column.
Follow that line right to the column under the design
subcooling value. Where the two intersect is the
required liquid line temperature.
Alternately you can convert the liquid line pressure gauge
reading to temperature by finding the gauge reading in
Temperature - Pressure Chart and reading to the left, find
the temperature in the °F Column.
5.
The difference between the thermometer reading and
pressure to temperature conversion is the amount of
subcooling.
Add charge to raise subcooling. Recover charge to lower
subcooling.
Subcooling Formula = Sat. Liquid Temp. - Liquid Line
Temp.
EXAMPLE:
A. Liquid Line Pressure = 417
B. Corresponding Temp. °F. = 120°
C. Thermometer on Liquid line = 109°F.
To obtain the amount of subcooling subtract 109°F from
120°F.
The difference is 11° subcooling. See the specification
sheet or technical information manual for the design
subcooling range for your unit.
