The chiller selector is the heart of the application that determines which chillers meet the building cooling load requirements and selects the combination of chillers that operates the most efficiently. The application does not start a chiller unless it has what it needs to support the function, such as chilled water flow, condenser water flow, and tower flow. The application can also consider chiller runtimes and start counts.
Device Information Table (Chiller Selector)
To provide automated, efficient operation, you must include the energy description of each chiller during CCT configuration. This description consists of some or all of the Rated Capacity, Rated Current, Minimum CW Flow, Rated CW Flow, Minimum CHW Flow, Rated CHW Flow, Peak COP, Device Type, CHW MAX Flow, Lift Sensitivity, Design Lift, Max Pct Load, Min Pct Load, Max Pct Load COP, Min Pct Load COP, Interstage Transition Delay, and Stabilize Time, depending on the chosen control mode and chiller plant configuration.
The user enters this information during CCT configuration. After the CCT tree selection process, the user must edit the Details of the Chiller Selector module. In the CCT canvas, under Output Control, search and double-click (or right-click and select View Details) the corresponding Chiller Selector # primitive, where # is the number of chillers of the plant. Then, edit and enter the required values according to the Device Information Table.
The following parameters are supplied by the CW Selector, PCHWP Selector, and Tower Selector and are used with the flows defined in the Device Information Table.
| Input | Description |
|---|---|
|
CW Commanded Flow |
This value must be greater than CW Min flow defined in the Device Info Table before the chiller can be commanded on. |
|
CW Available Flow |
Indicates the flow available based on CW pumps enabled and their flow capacity. |
|
CHW Commanded Flow |
This value must be greater than CHW Min flow defined in the Device Info Table before the chiller can be commanded on. |
|
CHW Available Flow |
Indicates the flow available based on CHW pumps enabled and their flow capacity. |
|
Tower Commanded Flow |
This value must be greater than CW Min flow defined in the Device Info Table before the chiller can be commanded on. |
|
Tower Available Flow |
Indicates the flow available based on Towers enabled and their flow capacity. |
| Output | Description |
|---|---|
|
Required CW Flow |
Indicates the chiller rated flows sent to the CWP Pump Selector. |
|
Min CW Flow Setpoint |
Indicates the minimum flow required for safe chiller operation. |
|
Required CHW Flow |
Indicates the chiller rated flows sent to the PCHWP Pump Selector. |
|
Min CHW Flow Setpoint |
Indicates the minimum flow required for safe chiller operation. |
|
Max CHW Flow |
Indicates the sum of the rated CHW Max Flow of all chillers requested. It is the maximum amount of variable speed CHW flow that the Chiller Selector is allowing the Variable Speed Pump Selector to command for each chiller. In a variable speed primary system, this value sets the upper limit for primary pumps being controlled by the PCHWP Selector. In a primary-secondary system, this value sets the upper limit for the secondary pumps being controlled by the SCHWP Selector. |
|
Required Tower Flow |
Indicates the chiller rated flows sent to the Cooling Tower Selector. |
|
Property |
Must Be Entered |
|---|---|
|
Rated Capacity (X) 1 Peak COP (X) |
Always |
|
Rated CHW Flow (X) CHW Min Flow (X) |
If the pumps are headered |
|
CHW Max Flow |
If system has variable speed primary pumps |
|
Rated Current Power (X) |
If Control Mode = Chiller Load (Required for ASHRAE Open Loop Tower Control) |
|
Rated CW Flow (X) CW Min Flow (X) |
If Condenser Pump Piping Layout = Parallel |
|
Design Lift (X) |
If Lift Sensitivity ≠ 0 |