The following table describes the attributes used by the Cooling Tower Selector modules:
|
Name |
Type 1 |
Description |
Default Value |
|---|---|---|---|
|
Available Capacity |
V |
Provides the sum of the capacities of the enabled towers. |
0 Display units come from Flow Units. |
|
Current Capacity |
G, V |
Provides the sum of the capacities of the devices currently on (that is, Device nn Status = On). |
0 Display units come from Flow Units. |
|
Current Efficiency |
V |
Indicates the capacity weighted efficiency of the devices currently commanded to On. |
0 Display Units: % |
|
Current/Power Units |
Indicates the units used for the current/power. These units are not currently used. |
A Set Name: Unit |
|
|
CW Commanded Flow |
Indicates the capacity of the active condenser water pumps. The Pump Selector provides this value, if used. The Cooling Tower Selector uses the maximum of Process Variable and CW Commanded Flow to determine when to start and stop the cooling towers. |
0 Display units come from Flow Units. Minimum Value: 0 |
|
|
Device Info |
Provides a structure of arrays containing individual information of each device. This structure contains: Rated Capacity, Rated Current/Power, and Peak Efficiency. |
||
|
Device nn Capacity |
Indicates the flow capacity of each device in selectable units (where nn is 01-08). |
||
|
Device nn Cmd |
V |
Provides the request commands to each cooling tower (where nn is 01-08). |
False |
|
Device nn Enable |
Indicates the Disable/Enable state of the devices (where nn is 01-08). |
True |
|
|
Device nn Runtime |
Indicates the runtimes of the devices (where nn is 01-08). |
0 Display Units: Hours |
|
|
Device nn Start Count |
Indicates the number of starts performed by each device (where nn is 01-08). |
0 |
|
|
Device nn Status |
Indicates the current Off/On state of the devices as reported by the hardware itself (where nn is 01-08). These inputs are used to enforce the Minimum On and Minimum Off times. |
Off Set Name: Off/On |
|
|
Flow Units |
Indicates the units used for the flow depending on the Units of the application. |
l/s, gpm Set Name: Unit |
|
|
Interstage Off Delay |
Delay after an Off command before starting to downstage again. |
15 Display Units: Min Range: 0.1-120 |
|
|
Interstage On Delay |
Delay after an On command before starting to upstage again. |
15 Display Units: Min Range: 0.1-120 |
|
|
Iso Valve nn Cmd |
V |
Provides the request commands to each cooling tower isolation valve (where nn is 01-08). |
False |
|
Iso Valve Stroke Time |
Indicates the amount of time that the Cooling Tower Selector waits from the time the it opens the isolation valve to the time it commands the tower fan on. |
25 Display Units: Sec Range: 0-120 |
|
|
Low Load |
Indicates the only operating chiller has been commanded off to provide chilled water more efficiently. |
False |
|
|
Min Off Time |
Indicates the minimum amount of off time applied to all cooling towers. |
1 Display Units: Min Range: 0-60 |
|
|
Min On Time |
Indicates the minimum amount of on time applied to all cooling towers. |
1 Display Units: Min Range: 0-60 |
|
|
Peak Efficiency |
Indicates the peak efficiency of each cooling tower. The Cooling Tower Selector chooses the devices with the highest value first. |
85 Display Units: % Range: 50-100 |
|
|
Predicted Adjusted Efficiency |
SC, V |
Indicates the Predicted Efficiency of the Required Devices (steady state device commands) adjusted for runtime imbalances, start count imbalances, start/stop differences, and start/stop efficiency penalties. |
0 Display Units: % |
|
Predicted Efficiency |
SC, V |
Indicates the expected efficiency based on the Required Devices. |
0 Display Units: % |
|
Process Variable |
Provides the required tower flow from the Chiller Selector. |
0 Display units come from Flow Units. |
|
|
Rated Capacity |
Indicates the cooling capacities of each device. |
0.1 Display units come from Flow Units. |
|
|
Rated Current/Power |
Indicates the rated current of each device. |
0 Display units come from Current/Power Units. |
|
|
Required Devices |
SC, V |
Provides an integer output representing the packed bits of the desired steady state set of towers commanded On. For example, a value of 88 means: 0-1-0-1-1-0-0-0 which indicates device 4, 5, and 7 are On, and the rest are Off. |
0 |
|
Required Interim Devices |
SC, V |
Provides an integer output representing the packed bits of the intermediate devices requested to turn on while the Cooling Tower Selector moves toward the desired steady state. |
0 |
|
Rotate Now |
Causes an immediate re-evaluation of the required devices to provide the required capacity to meet the current required flow based on the current Device Runtime or Start Counts or both. |
False |
|
|
Rotation Mode |
Determines how rotation is processed:
|
None Set Name: Rotation Mode |
|
|
Sequence Row |
Indicates the sequence table row number that the module attempts to move toward while following device timers and statuses. This input is available when the Sequence Row Control input is True. If the input value is out of range or if a sequence table is not present, Sequence Row input is ignored. |
0 |
|
|
Sequence Row Control |
Enables Sequence Row parameter to enable devices. | False | |
|
Sequence Row Transition Delay |
When Sequence Row becomes False, this indicates the amount of time the selector does not make any staging decisions.
Note: This time is ignored when System Enabled becomes False.
|
Default: 0.2 minutes Minimum: 0.1 minutes |
|
|
System Enabled |
Disables/enables the Cooling Tower Selector. When System Enabled is False, the Cooling Tower Selector downstages to zero capacity. Note: When False, the isolation valves to the towers are closed.
|
False |
|
|
Total Current/Power |
V |
Indicates the total actual current/power output of all currently operating devices. |
0 Display units come from Current/Power Units. |