Trane RTWA 70-125 TON - Manual (Page 85)

RLC-SVD03A-EN 85
Other Service Features
Service Pumpdown
The UCM provides for a "onetime" Service Pumpdown mode, in which a
service-technician can direct a particular compressor to start and run for one
minute, to accomplish pumpdown of the low side of the refrigeration system
(evaporator and EXV).
To aid in accomplishing this pumpdown, certain noncritical diagnostics will be
ignored or disabled during this mode. Critical diagnostics such as those
associated with motor protection, high pressure, and chilled water flow, will
still be' enforced and may prevent or terminate the sequence.
Service Pumpdown Procedure
1. Place the Chiller in the Stop Mode using the Stop Button on the CLD and
allow the Chiller, if currently running, to go through its shutdown
sequence.
2. Manually close the liquid line shutoff valve on the circuit to be pumped
down.
3. Use the CPM's Operator Interface to begin the mode specifically for the
compressor/circuit you wish to pumpdown by selecting and "Enabling" it
in the Service Tests Group. The CLD will then be displaying an Operating
Code for Service.
4. The UCM shall then begin the start sequence (without restart inhibit) and
turn on the selected compressor once the EXV has opened to its pre-
position. The compressor shall run for a period of 1 minute at its mini-
mum load and the condenser fans will stage under normal fan control.
The UCM will automatically shut off the compressor and condenser fans,
close the EXV, and return the chiller to the normal stop mode once the 1
minute timer has expired. The pumpdown sequence cannot be repeated
again without a UCM power down reset.
NOTE: The unload solenoid is always kept energized for approximately 1
hour after any compressor shutdown and the oil sump heater is continuously
energized.
5. Manually close the discharge line shutoff valve and the oil line shutoff
valve.
6. Remove all power to the chiller and service as required.