Maintenance
142 RTAC-SVX01J-EN
3. Close valve, remove charging hose and start unit.
Monitor subcooling.
4. If subcooling is still insufficient, return to step #1.
Note: Proper subcooling can be determined from run log
history, service experience, or by contactingTrane
technical service.
Charge Isolation in the high or
low side of system
All the refrigerant may be trapped into the high side
(condenser) of the unit for maintenance on the
compressor or low side.With the suction line service valve
option, charge may also be isolated in the evaporator for
maintenance on the compressor or the high side. It is
preferable to isolate the charge in the evaporator, if this
option is available.
High side charge isolation procedure
1. Make sure circuit is off.
2. Shut liquid line service valve.
3. Shut oil return line service valve.
4. In compressor service view, select pumpdown for the
required circuit.
• Chilled water pump commanded on
• All fans will turn on
• EXV will open 100%
• Oil return line solenoid (if included) will open
• Unit will start at minimum load
• Unit will run until one of the following occurs:
• Pumpdown timer registers a maximum of 4
minutes (single compressor circuit) or 8 minutes
(manifolded compressor circuit)
• Suction pressure as read from the transducer on
single compressor circuit, or lower of the two
transducers on a manifolded circuit, falls below
20 psia
• Monitor pressure with a suction gauge
5. When unit trips, the discharge check valve will close.
6. Close discharge isolation valve.
7. Close oil line shut off valve.
8. Recover the remainder of the refrigerant.
Note: Remaining vapor can be recovered/stored in the
high side of the system. Be certain to follow proper
recovery procedures to avoid introduction of non-
condensable gases.
9. The low side and compressor may be serviced at this
time.
Note: Units with a design sequence of A0 did not have
enough capacity in the condenser to hold the entire
charge. Table 64. lists the amount of charge that
would flood the oil separator if the charge was
isolated in the high side. For this reason, when
getting the unit back to running condition, care
must be taken to drive the refrigerant out of the oil
separator using the oil separator heaters.
Returning unit to running condition
1. Open all valves.
2. Manually open EXV for 15 minutes to allow refrigerant
to drain to evaporator by gravity (ensure water is
flowing in the evaporator prior to opening the EXV).
3. Let unit sit with heaters on to drive refrigerant out of oil
and warm up compressor bearings. Depending upon
ambient conditions, this may take up to 24
hours.Ensure the UCM is powered so the pump may be
energized if it detects a freeze condition.
4. Once the oil level has returned to normal, the unit can
be put back into operation.
Low side charge isolation procedure
After normal shut down under some conditions most of
the charge resides in the evaporator. Running cold water
through the evaporator may also drive much of the
refrigerant to the evaporator.
1. Make sure circuit is off.
2. Close suction line isolation valve.
3. Close oil return line service valve.
4. Close liquid line service valve.
5. Manually open EXV.
6. Use a liquid pump or vacuum pump to move
refrigerant from the condenser to evaporator.The
liquid pump will only be effective if there is a lot of
Table 64. Charge holding capabilities on high side
Nominal
Circuit
Capacity
Nominal
Circuit
Charge
lb
Condenser
Charge
Holding
Capacity @
60% full
90
o
ambient
lb
Charge in
Oil
Separator
lb
% Oil
Separator
Level
70 165 118.1 46.9 97.7
85 175 134.3 40.7 86.0
100 215 163.7 51.3 56.0
120 225 187.9 37.1 41.2
170 365 203.4 161.6 100.0%
200 415 282.0 133 86.1 %
240 460 325.6 134.4 86.9 %
Note: Circuit varies slightly with efficiency and unit configuration
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