4
d) If, when the unit is run, symptoms of loss of charge (for
example, low pressure switch tripping or abnormally
low cooling capacities) are detected, first conduct a
leak test. For the latter all refrigerant must be removed
from the circuit. Transfer the refrigerant to a storage
tank and then clean the circuit as described earlier.
e) Before adding the refrigerant charge proceed as follows:
-
Draw a vacuum in the refrigerant circuit until a
pressure of 667 Pa (-7 mm Hg) has been reached
for at least two hours. At a greater distance between
units the period must be longer.
the period of time
of the vacuum is important.
-
Check that there are no refrigerant leaks.
Continue to charge refrigerant as described below:
Total charge = unit charge plus additional charge per
metre suction line and per metre liquid line.
-
The refrigerant charge for the 38UQZ and 40ALZ
units is given in Table 1 - Physical Data.
-
For each metre of refrigerant connection line
installed, refrigerant has to be added in accor-
dance with the table below for the liquid and gas
lines:
Table 7 - Refrigerant charge (g/m)
Diameter
1/2” 5/8”
3/4”
7/8”
1-1/8” 1-3/8”
Liquid line
75
120
180
250
420
645
Suction line
14
23
34
47
81
123
OIL RECHARgE
If any oil needs to be added to fill the siphons and above
all when the total line length is high, use the same type and
brand as used in the compressors.
START-UP
Necessary checks/precautions before start-up:
•
Confirm that the electrical power source agrees with
the unit nameplate rating.
•
Ensure that the power connections between speed and
thermostat have been made and correctly tightened.
•
Check that there are no refrigerant leaks in the soldered
refrigerant lines, and that the refrigerant and oil charges
are correct.
•
Check the 40ALZ drain connection and that the water
is drained correctly.
•
Ensure that the unit is level and well-supported.
•
Check for proper fan rotation direction
•
Check the condition of the ductwork in case damage
has occurred during installation.
•
The air filter should be clean and in place.
•
All the panels should be fitted and firmly secured with
the corresponding screws.
•
Make sure that compressors float freely on the mount-
ing springs.
WARNING: The compressors are mounted on vibration
isolators. Do not loosen or remove the support mounting
bolts.
IMPORTANT: Actual start-up should only be done under
the supervision of a qualified refrigeration mechanic.
Initial checks
With the unit in operation, ensure that the values shown
on the high and low pressure gauges are within the normal
limits. It is advisable to simulate unit shutdown due to high
and low pressure, in order to make sure that the pressure-
stats work properly. To do so, proceed as follows with the
unit operating in cooling mode:
•
High pressure shutdown:
Completely cover the outdoor
air inlet, or disconnect the outdoor fan and motor. The
unit should stop at a pressure of 844 kPa.
•
Low pressure shutdown:
Cover the indoor air inlet, or
disconnect the indoor fan and motor. Observe the low
pressure gauge. The unit should stop at a pressure of
6 kPa.
The pressure switches are automatically reset. As this takes
some time, the unit will stop, the pressures will equalise, and
then the unit will be reset and will start up again.
Check that the motor and compressor consumptions are
approximately the same as those shown in the fan perfor-
mance curves and in the cooling capacity tables for the unit
operating conditions (indoor and outdoor temperatures,
air flow and static pressures, based on the speed, etc.).
