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SECTION 2: SEQUENCE OF OPERATIONS
Main Chiller Controller Technical Guide
24
Economizer Subcool Module & Main Faults
Economizer Subcool Module
The Economizer Subcool Module manages the superheat of the
sub-cooler to a settable limit. The Economizer Subcool Module will
receive its run/stop from the Compressor Circuit Module.
Points of Information and Control
The Economizer Subcool Module provides the following critical
points of information (beyond general status) to the Main Chiller
Controller via E-BUS (Modbus):
Commands
Economizer-Run
– This is a binary condition to run or stop
the economizer operation.
Status’s
Startup-Status
– This is a binary indication that this board
has completed all steps required for complete startup, including
all valve positioning operations.
Running-Status
– This value should indicate if the compressor
is running at, beyond, or below the demand.
Fault-Status
– This value should indicate any faults in the
compressor or within this module, including indication that the
Disable binary input is active.
Shutdown-Status
– This is a binary indication that the board
has completed all steps required for complete shutdown, including
all valve positioning operations.
Run-time
– This value is an accumulation of running hours for
the attached compressor.
Sequence
Startup
When Economizer-Run is activated, open the EXV to the initial
starting position and hold for a settable time delay.
Modulation
Using a PID loop, modulate the EXV to obtain the set superheat
value desired.
Shutdown
When Economizer-Run is deactivated, close the EXV.
Fault Detection
The Main Chiller Controller continuously performs self diagnostics
during normal operation to determine if any operating failures have
occurred.
These failures (faults) can be reported to the Panel PC with Touch
Screen interface or to a computer running Prism 2 software.
The following are the available fault designations for the Main
Chiller Controller:
No Flow
No Water Flow has been detected once the
butterfl y valve has been opened.
Exp Lost
One or more expansion boards aren’t
communicating with the main controller.
CondFail
The condenser fault input has been lost so
that indicates an alarm. This doesn’t aff ect
control.
Shutdown
Either the Emergency Stop or the Phase Loss
inputs on the Main Controller have set this
condition or a Refrigerant Leak on the
Chiller Expansion Module has occurred.
CompFail
This alarm indicates a compressor fault has
been received on the EBUS from the
Main Controller.
Disabled
This alarm indicates the Binary Input on the
Compressor Module is not made.
Freeze
This alarm indicates the water temperature is
below the Leaving Water Temperature
Setpoint.
LostComm
This alarm should never occur, but just in case, it
means there is no communication with the
CommLink 5.
No Flow Fault
The rate of fl ow is monitored when the Butterfl y Valve opens. If the
Butterfl y Valve is 100% open and the fl ow rate in Gallons Per Minute
(GPM) is not at or above a proving level of 320 GPM (adjustable)
it will not enable the Proof of Water Flow indicator, and cooling
will be disabled.
If the Proof of Flow was enabled by adequate GPM’s and the fl ow
rate drops below a lower limit of 290 GPM (adjustable) for at least
3 seconds, the Proof of Flow enable will be removed.
If the Proof of Flow is not enabled, the cooling will not be allowed
to activate. If the cooling was currently running and the Proof of
Flow was lost, the cooling will be de-activated until such time as
the GPM rise above the proof level again.