18
Controls
Standard Protections
Standard Protections
The chiller controller uses proportional-integral-derivative (PID) control for all limits—there is no
dead band. This removes oscillation above and below setpoints and extends the capabilities of the
chiller.
Some of the standard protection features of the chiller controller are described in this section. There
are additional protection features not listed here. Contact your local Trane offi ce for additional
protection information.
High Condenser-Pressure Protection
The chiller controller’s condenser limit keeps the condenser pressure under a specifi ed maximum
pressure. The chiller will run up to 100 percent of this setpoint before the Adaptive Control mode
reduces capacity.
Starter-Contactor Failure Protection
The chiller will protect itself from a starter failure that prevents the compressor motor from
disconnecting from the line to the limits of its capabilities.
The controller starts and stops the chiller through the starter. If the starter malfunctions and does
not disconnect the compressor motor from the line when requested, the controller will recognize
the fault and attempt to protect the chiller by operating the evaporator-and condenser-water
pumps and attempting to unload the compressor.
Loss of Water-Flow Protection
Tracer AdaptiView
TM
control has an input that will accept a contact closure from a proof-of-fl ow
device such as a fl ow switch or pressure switch. Customer wiring diagrams also suggest that the
fl ow switch be wired in series with the cooling-water (condenser-water) pump starter’s auxiliary
contacts. When this input does not prove fl ow within a fi xed time during the transition from Stop to
Auto modes of the chiller, or if the fl ow is lost while the chiller is in the Auto mode of operation, the
chiller will be inhibited from running by a nonlatching diagnostic.
Evaporator Limit Protection
Evaporator Limit is a control algorithm that prevents the chiller tripping on its low refrigerant-
temperature cutout. The machine may run up to the limit but not trip. Under these conditions the
intended chilled-water setpoint may not be met, but the chiller will do as much as it can. The chiller
will deliver as much cold water as possible even under adverse conditions.
Low Evaporator-Water Temperature
Low evaporator-water temperature protection, also known as Freeze Stat protection, avoids water
freezing in the evaporator by immediately shutting down the chiller and attempting to operate the
chilled-water pump. This protection is somewhat redundant with the Evaporator Limit protection,
and prevents freezing in the event of extreme errors in the evaporator-refrigerant temperature
sensor.
The cut out setting should be based on the percentage of antifreeze used in the customer's water
loop. The chiller’s operation and maintenance documentation provides the necessary information
for percent antifreeze and suggests leaving-water temperature-cutout settings for a given chilled-
water temperature setpoint.
CTV-PRC001-E4
