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Refrigerant charging
After the refrigeration pipework system has been pressure
tested and evacuated, and meets the vacuum pressure
requirements of paragraph <<Field evacuation>>, the
refrigerant may be charged as follows. Be sure to follow the
start-up procedure at the same as charging the refrigerant.
1. Loosely connect a cylinder of refrigerant to the 1/4" OD
Charging Valve Located on the liquid line.
2. Open and close the valve on the refrigerant cylinder to
purge the connection. Tighten the coupling nut.
3. Invert the refrigerant cylinder so that only liquid will enter
the system
4. Allow the compressor to continue running throughout the
remainder of the charging operation. Do not allow the
pressure to fall bellow 0.15 bar.
Caution:
Do not attempt to start the compressor by blocking the
safety controls. Allow the condensing unit to function
in a normal manner.
5. Allow the system to continue functioning for approximately
30 minutes. If during this period bubbles appear in the
liquid line sight glass, add refrigerant.
6.Leak-test the refrigerant circuit.
Start-up procedure
1. Start the unit by switching to <<On>>
2. After the unit has started, allow it to operate for at least
15 minutes to stabilise operating pressures. Then check :
- compressor oil level.
- compressor and fan motor power consumption.
- suction pressure.
- discharge pressure.
- liquid line sight glass.
- superheat.
- subcooling.
All readings and measurement should be logged.
Procedures are given below.
CAUTION
PHASE ROTATION IS CRITICAL
IF SUCTION PRESSURE DOSE NOT FALL TO EXPECTED
OPERTATING LEVEL WITHIN THIRTY (30) SECONDS
AFTER COMPRESSOR IS STARTED, COMPRESSOR
ROTATION MAY BE REVERED.
TO REVERSE ROTATION, DISCONNECT ALL UNIT POWER
AND REVERSE ANY TWO (2) INCOMING POWER LEAD
WIRES AT THE UNIT HIGH VOLTAGE TERMINAL BLOCK.
RECONNECT ALL UNIT POWER, RESTART UNIT, AND
RE-CHECK SUCTION PRESSURE.
Refrigerant charge
Suction pressure
Liquid pressure
Liquid
Suction
R-22
R-407C
Line
Line
Bottom tank
Note : R-407C refrigerant charge must be liquid phase only.
Installation
Suction pressure
Liquid pressure
Bottom tank
Liquid
Suction
Line
Line
11
Oil level
Oil should be visible in the compressor, under full load, in
the compressor oil level sight glass. The unit was charged
with the proper amount of oil before shipping. Under normal
operation, compressor oil is always expected to return to
compressor oil sump, and no additional oil should be added.
For oil level indication, refer to compressor oil sight glass, as
per Figure 3 . If oil is within sight glass visibility, oil quantity
should be sufficient.
Refrigerant pressures
Observe operating pressures. If pressures are above or
below normal see <<Trouble Analysis>> section. Normal
operating pressures are in Table 2. A High & Low pressure
settings are found in Table 1
Liquid line sight glass (Optional)
The flow of refrigerant through the sight glass should be
smooth and without bubbles. Bubbles indicate a refrigerant
shortage and probably a leak, or a restriction in the liquid
line.
Superheat
Normal Superheat is 6 to 8 deg C. Overfeeding of the
evaporator results in high suction pressure, low superheat
and possible liquid carryover. Inadequate or too high a
superheat is remedied by adjusting stem on the thermostatic
expansion valve (TEV). If this fails to correct the condition,
then the valve cage or power element of the TEV may be
defective and should be replaced.
Caution:
1. Excessive foaming indicates the presence of
refrigerant in the oil and will result insufficient
compressor lubrication. Turn off the motor and
investigate the cause.
2. An excess of the oil in the compressor can cause
problems in the same way as a lack of oil. Before
topping up , contact a qualified service technician.
Use only Tranerecommended oils.
Figure 3
- Compressor oil level
WARNING
1. Do NOT run the compressor on reverse rotation
2. Do NOT perform any pump down cycle with Scroll
compressor
3. Do Not run the compressor below the setting of low
pressure switch
4. Do NOT by pass any safety devices when operating the
system.
Failure to observe any of the above will cause severe
damage to the Scroll compressors.
Maximum
oil level
Minimum
oil level
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