Trane RTWA 70-125 TON - Manual (Page 20)

20 RLC-SVD03A-EN
Compressor Start/Stop
To start a compressor after either a “normal' shutdown, a Diagnostic reset, or
power-on-reset, the following sequence will occur:
1. On a call for a compressor, the Restart Inhibit Timer will time out, if any
time remains.
2. The EXV is positioned to the initial closed start position. At the same
time, the unload solenoid is energized and the load solenoid is de-ener-
gized. Timing is determined by the time required to position the EXV
3. After the EXV is positioned:
• the compressor is turned on
• the compressor heater is de-energized
• the saturated evaporator ref. temp. cutout ignore time is set, based on
the saturated condenser temperature. Prior to start, the condenser tem-
perature approximates the ambient temperature.
• the fan control algorithm is executed
To stop a compressor due to either the Stop button on the CLD or an
External/Remote “STOP”, the sequence shall be as follows:
1. The unload solenoid is energized for 20 seconds and the load solenoid is
de-energized. The compressor continues to run for the remaining 20 sec-
onds. This is defined as the RUN:UNLOAD mode.
2. The compressor and the fans are turned off. The crankcase heater is
energized.
3. The unload solenoid remains energized for 60 minutes after the compres-
sor stops. The load solenoid is de-energized.
4. The EXV is closed. Closing begins at maximum speed when the com-
pressor is turned off. (Max. speed is 25 steps per second, full stroke is
757 steps.
5. After 60 minutes, the unload solenoid de-energizes.
The RUN:UNLOAD mode is also used to stop a compressor due to normal
LWT control, Low Ambient Run Inhibit, or Freeze Avoidance.
A compressor stop due to any diagnostic will skip step 1 above and go
directly to step 2.