Free Cooling Relay Checkout - Trane CVHE Troubleshooting Manual

command from Tracer will initiate the sequence to enter FC.
If the chiller is in AUTO and not running UCP2 will start the condenser water pump just as it
does for powered cooling (Since the unit is in AUTO the chilled water pump should already
be running. Once condenser water flow is confirmed the FC valve relays #1, #2, and the FC
Aux. relay are all energized. If the FC valve closed limit switches do not open within 3
minutes a MMR diagnostic is generated. Once the FC valve closed limit switches open the
unit is considered in FC.
If the chiller is in AUTO and is running powered cooling, the chiller will do a normal friendly
shutdown when FC is commanded from either source. The compressor will enter RUN:
UNLOAD, POST LUBE, and overdrive the IGVs closed as usual. Once the IGV's have been
overdriven closed and condenser water flow has been confirmed, the three FC relays will be
energized.
In FC manual vane control shall not be active.
It is not necessary to check the status of the IGVs during FC. The IGVs must be closed
during FC; it is sufficient to assume that they are closed since they are overdriven closed on
all compressor shutdowns and hard (powerup) resets.
Once the FC valves have opened, a FC valve closure will generate an MMR diagnostic.
If there is a diagnostic in FC, Stop FC as normal and Stop the Condenser Water Pump.
5 FC can be terminated from either the Front Panel CLD, the Ext. FC Switch input at the
Options module, or the Tracer (or a diagnostic). Once commanded to Off, the Two FC relays
are de-energized. If the FC valve closed limit switches do not close within 3 minutes a MMR
diagnostic is generated. Once the limit switches are closed the chiller status should revert
back to AUTO and powered cooling may be entered if there is a call for cooling.
6 On all FC chillers (FC is installed), the FC valve limit switches must be closed to both start
and run powered cooling, otherwise a MMR diagnostic will be generated. The IGVs must be
held closed for 3 minutes on each startup following a free cooling mode.
7 On FC units the failure of communications between the Options module and the Chiller
module will cause a MMR diagnostic at the Chiller module.
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