Trane CVGF Standard Protections, High Condenser-PressureProtection, Loss of Water-FlowProtection

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 AdaptiViewTM 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

flow 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.

18 CTV-PRC001-E4