13
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.
SUBCOOLING FORMULA = SATURATED LIQUID LINE
TEMPERATURE - LIQUID LINE TEMPERATURE
Checking Superheat
EXAMPLE:
a. Suction Pressure = 143 PSI
b. Corresponding Temp. = 50°F
c. Thermometer on Suction Line = 59°F
To obtain the degrees temperature of superheat, subtract
50.0 from 59.0°F. The difference is 9° Superheat. The 9°
Superheat would fall in the ± range of allowable superheat.
SUPERHEAT = SUCTION LINE TEMP - SAT. SUCTION
TEMP.
Superheat Adjustment
NOTE: Superheat adjustments should not be made
until indoor ambient conditions have stabilized.
This could take up to 24 hours depending on
indoor temperature and humidity. Before checking
superheat, run the unit in cooling for 10-15
minutes or until refrigerant pressures stabilize.
Use the following guidelines and methods
to check unit operation and ensure that the
refrigerant charge is within limits.
For TXV systems, to adjust superheat, unscrew the cover
from the expansion valve, locate the adjustment screw, and
turn it clockwise (in) to increase superheat or counterclock
-
wise (out) to decrease superheat. It is recommended to
make small adjustments at a time, 1/8-1/4 turn increments.
Replace adjustment cap. Wait a minimum of 10 minutes
between adjustments to allow time for the TXV and pres
-
sures to stabilize.
Refrigerant Charge Check
NOTE: For optimal performance, follow charging
instructions below.
Units with (TXV) Device
Single Stage Cooling Application: Refer to the Design Su
-
perheat & Subcooling table
Two-Stage Cooling Application: Run unit on Low Stage
cooling and refer to Design Superheat & Subcooling table.
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. System should
have a subcooling and superheat within the range
listed on the Design Superheat and Subcooling
table.
a. If subcooling and superheat are low, adjust TXV
superheat, then check subcooling.
NOTE:
To adjust superheat, turn the valve stem
clockwise to increase and counterclockwise to
decrease.
b. If subcooling is low and superheat is high, add
charge to raise subcooling then check superheat.
c. If subcooling and superheat are high, adjust TXV
valve superheat, then check subcooling.
d. If subcooling is high and superheat is low, adjust
TXV valve superheat and remove charge to lower
the subcooling.
NOTE:
Do NOT adjust the charge based on suction
pressure unless there is a gross undercharge.
4. Disconnect manifold set, installation is complete.
Design Superheat & Subcooling
Model
Superheat
±2°F
Subcooling
±1°F
Expansion
Device
Cooling
Stage
Outdoor
ambient (°F)
GPHM56041
15
10
Fixed TXV
Low
82
START-UP PROCEDURES AND CHECKLIST
WARNING
HIGH VOLTAGE!
Disconnect all power before
servicing or installing this unit.
Multiple power sources may be
present. Failure to do so may cause
property damage, personal injury or
death.
Begin with power turned off at all disconnects.
Air Conditioning Start-Up Procedure
1. Turn thermostat system switch to “Cool,” and fan
switch to “Auto” and turn temperature setting as high
as it will go.
2.
Inspect all registers and set them to the normal open
position.
3. Turn on the electrical supply at the disconnect.
4. Turn the fan switch to the “ON” position. The blower
should operate after a 7 second delay.
5. Turn the fan switch to “AUTO” position. The blower
should begin ramping down after an approximate
60-second delay.
6. Slowly lower the cooling temperature until the unit
starts. The compressor, blower, and fan should now
be operating. Allow the unit to run 10 minutes, make
sure cool air is being supplied by the unit.
7.
Turn the temperature setting to the highest position,
stopping the unit. The indoor blower will continue to
run for approximately 60 seconds.
