Trane CVGF manual Controls, Extended Operation Package, Optional Features, Base-LoadingControl

Controls

Optional Features

Extended Operation Package

Select the extended-operation package for chillers that require external, hot water control, and/or base-loading capabilities. This package also includes a 4-20 mA or 0-10 Vdc analog input for a refrigerant monitor.

•External base-loading control

•External base-loading relay

•External hot-water control relay

•Refrigerant monitor input

Base-Loading Control

This feature allows an external controller to directly modulate the capacity of the chiller. It is typically used in applications where virtually infi nite sources of evaporator load and condenser capacity are available and it is desirable to control the loading of the chiller. Two examples are industrial process applications and cogeneration plants. Industrial process applications might use this feature to impose a specifi c load on the facility’s electrical system. Cogeneration plants might use this feature to balance the system’s heating, cooling, and electrical generation.

All chiller safeties and Adaptive Control functions are in full effect when Base Loading is enabled. If the chiller approaches full current, the evaporator temperature drops too low, or the condenser pressure rises too high, the controller’s Adaptive Control logic limits the loading of the chiller to prevent the chiller from shutting down on a safety limit. These limits may prevent the chiller from reaching the load requested by the Base Loading signal.

An alternative and less radical approach to Base Loading indirectly controls chiller capacity.

Artifi cially load the chiller by setting the chilled-water setpoint lower than it is capable of achieving. Then, modify the chiller’s load by adjusting the current-limit setpoint. This approach provides greater safety and control stability because it leaves the chilled-water temperature-control logic in effect. The chilled-water temperature control responds more quickly to dramatic system changes and limits chiller loading prior to reaching an Adaptive Control limit.

Hot-Water Control

This feature allows an external controller to enable/disable and modulate the hot-water control mode. Occasionally, centrifugal chillers are used to provide heating as a primary mission. In this case the external controller or operator would select a hot-water temperature setpoint and the chiller capacity would be modulated to maintain the setpoint. Heating is the primary mission and cooling is a waste product or a secondary mission. This technique provides application fl exibility, especially in multiple-chiller plants in conjunction with undersized heating plants.

The chiller needs only one condenser for hot-water control, whereas Heat Recovery uses a secondary condenser.

Refrigerant Monitor

The Extended Operation package allows for a refrigerant monitor to send a 4-20 mA signal to the Tracer AdaptiViewTM control display. It can be calibrated to correspond to either 0-100 ppm or 0-1,000 ppm concentration levels. The concentration level is displayed at Tracer AdaptiViewTM control, but the chiller will not take any action based on the input from the refrigerant monitor.

Alternatively, a refrigerant monitor can be connected to Tracer Summit, which has the ability to increase ventilation in the equipment room in response to high refrigerant concentrations.

CTV-PRC001-E4 17