SERVICING
17
2. Install a high side pressure gauge on the high side (liq-
uid) service valve at the front of the unit.
3. Record the gauge pressure and the temperature of the
line.
4. Review the technical information manual or specification
sheet for the model being serviced to obtain the design
subcooling.
5. Compare the hi-pressure reading to the “Required Liquid
Line Temperature” chart. 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 read
-
ing in the R-410A Pressure vs. Temperature Chart, find
the temperature in the °F. Column.
6. 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 PSIG
b. Corresponding Temp. = 120°F.
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 sub-
cooling range for your unit.
2 TON
10-12°F
3 TON
13-15°F
4 TON
8-10°F
5 TON
11-13°F
There are other causes for high head pressure which may
be found in the “Cooling / Heating Analysis Chart.”
If other causes check out normal, an overcharge or a sys-
tem containing non-condensables would be indicated.
If this system is observed:
1. Start the system.
2. Remove and capture small quantities of gas from the
suction line dill valve until the head pressure is reduced
to normal.
3. Observe the system while running a cooling perfor-
mance test. If a shortage of refrigerant is indicated, then
the system contains non-condensables.
SUBCOOLING ADJUSTMENT ON EEV APPLICATIONS
NOTE: Subcooling information is valid only while the unit is
operating at 100% capacity or 100% compressor speed in
CHARGE MODE.
Compressor speed is displayed under STATUS menu in the
thermostat.
1. Run system at least 20 minutes to allow pressure to
stabilize. During the adjustment of subcooling, ambient
temperature should be greater than 65°F and less than
105°F. If ambient temperature is out of range, don’t ad-
just subcooling.
2. For best results, temporarily install a thermometer on the
liquid line at the liquid line service valve. Ensure the
thermometer makes adequate contact and is insulated
for best possible readings. Use liquid line temperature to
determine sub-cooling.
3. The system subcooling should fall in the range shown in
following table. If not in that range, adjust subcooling
according to the following procedure.
a. If subcooling is low, add charge to adjust the subcool-
ing as specified in the following table.
2 TON
10-12°F
3 TON
13-15°F
4 TON
8-10°F
5 TON
11-13°F
b. If subcooling is high, remove charge to lower the
subcooling to specified range.
NOTE: Not more than 0.8 lb. (13 oz.) of refrigerant be add-
ed to the system at a time to achieve the target subcooling.
It is recommended adding 4 oz. refrigerant each time, then
wait 20 minutes to stabilize the system.
4. Disconnect manifold set. Installation is complete.
NON-CONDENSABLES
If non-condensables are suspected, shut down the sys-
tem and allow the pressures to equalize. Wait at least 15
minutes. Compare the pressure to the temperature of the
coldest coil since this is where most of the refrigerant will
be. If the pressure indicates a higher temperature than that
of the coil temperature, non-condensables are present.
Non-condensables are removed from the system by first
removing the refrigerant charge, replacing and/or installing
liquid line drier, evacuating and recharging.
COMPRESSOR BURNOUT
When a compressor burns out, high temperature develops
causing the refrigerant, oil and motor insulation to decom-
pose forming acids and sludge.
If a compressor is suspected of being burned-out, attach
a refrigerant hose to the liquid line dill valve and properly
remove and dispose of the refrigerant.
NOTICE
Violation of EPA regulations may result in fines
or other penalties.
