The following table describes the attributes used by the Pump Selector modules:
|
Name |
Type 1 |
Description |
Default Value |
|---|---|---|---|
|
Available Capacity |
V |
Provides the sum of the enabled pump derated capacities. |
0 Display units come from Capacity Units. |
|
Control Mode |
Determines how the pumps are controlled:
|
Constant Speed Set Name: Pump Control Mode |
|
|
Current Capacity |
G, V |
Provides the sum of the derated capacities of the devices currently on (that is, Device nn Status = On). |
0 Display units come from Capacity Units. |
|
Current Efficiency |
V |
Indicates the capacity weighted efficiency of the pumps currently commanded to On. |
2.0 Display Units: % |
|
Current Percent Load |
V |
Indicates the percent loading of the pumps currently commanded to On adjusted by the Derate Percent. For constant speed pumps, this value represents the percent of the flow being used to satisfy the current load requirements. For variable speed pumps, this value represents the percent of flow versus the total available flow. |
0 Display Units: % |
|
Derate Now |
Derates the rated flow of the currently operating devices and may force an upstage. This input may be triggered, for example, by the Saturation Status of the PID that controls the Bypass Valve. This input applies to only constant speed pumping systems, as possible pump malfunction may result in not meeting the flow requirements. The module calculates that a Derating Percent such as the Current Percent Capacity becomes 101%. For example, if a rising edge of the Derate Now occurs when the Current Percent Capacity is 80%, the On devices are assigned a Derating Percent of 20.8% (101-80)/101*100, and are effectively rated at 79.2% of their actual rating. This value forces an immediate upstage. The Derating Percent is set to zero for all devices at the rising edge of the Derate Reset input. The individual Derating Value nn (where nn is 01-08) are properties of the module. As this condition is usually indicative of a hardware issue, the Derate Now input (or its source) should be used to set an alarm in the BAS. |
False |
|
|
Derate Reset |
Resets the derating value to zero. The derate reset action is triggered at the edge of the module. See Derate Now. |
False |
|
|
Derating Value nn |
V |
Indicates the array of individual device derate values (where nn is 01-08). |
0 Display Units: % |
|
Device nn Capacity |
Indicates the flow capacities of each device in selectable units (where nn is 01-08). |
0 Display units come from Capacity Units. |
|
|
Device nn Cmd |
V |
Provides the command requests to each pump (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 Peak Efficiency |
Indicates the peak efficiency for the pumps as percentages (where nn is 01-08). This value is limited to integers between 50% and 100%. Combinations with devices that have higher peak efficiencies are preferentially selected during operation without regard for improving run time or start count imbalances. Only devices with the same Peak Efficiency have the ability to be balanced for run time and/or start counts. For example, if two devices have peak efficiencies X, and two other devices have peak efficiencies Y, the start count and runtime balancing happens among the devices with peak efficiencies X and among the devices with peak efficiencies Y, but not among all devices. This selection happens because the run time and start count adjustments are small decimal values that do not add up to one unit and the Peak Efficiencies are whole numbers. See Combination Efficiency. |
85 Display Units: % Range: 50-100 |
|
|
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). |
Off Set Name: Off/On |
|
|
Flow Units |
C |
Indicates the units used for the flow depending on the Units of the application. |
gpm Set Name: Unit |
|
Hysteresis |
Indicates the value of an additional efficiency penalty to be applied before a change is made. Larger values increase the stability of the combination currently operating while forcing a greater drop in efficiency before a switch is made. The adjusted efficiency of the new combination includes this Hysteresis. |
0.00 Display Units: % Range: 0.00-10.00 |
|
|
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 |
|
|
CHWP LOWER PCT LOAD, CWP LOWER PCT LOAD, PCHWP LOWER PCT LOAD, SCHWP LOWER PCT LOAD (Lower Optimal Pct Load) |
Indicates the nominal value that applies to all pumps collectively. This value is the left hand endpoint of the pump efficiency plateau. When this value decreases, the application stages down at lower percent loads. For example, a plant runs pumps with a combined capacity of 400 gpm. When the Lower Percent Load is 70%, the application considers staging down when the current required flow reduces to less than 280 gpm. If this value is reduced to 55, the application does not consider staging down until the required flow decreases to less than 220 gpm. |
78 Display Units: % |
|
|
CHWP UPPER PCT LOAD, CWP LOWER PCT LOAD, PCHWP LOWER PCT LOAD, SCHWP LOWER PCT LOAD (Upper Optimal Percent Load) |
Indicates the nominal value that applies to all pumps collectively. It is the right hand endpoint of the pump efficiency plateau. |
98 Display Units: % |
|
|
Maximum Flow |
For Variable Speed Mode, this input provides a maximum limit on the pumping capacity (flow) that can be turned On to prevent more capacity than required by the enabled chillers. Maximum Flow takes precedence over Minimum Flow; therefore, when this input is zero, all pumps shut off. |
1e30 Display units come from Flow Units. |
|
|
CHWP-MINOFFTIME, CWP-MINOFFTIME, PCHWP-MINOFFTIME, SCHWP-MINOFFTIME (Min Off Time) |
Indicates the minimum amount of off time applied to all pumps. |
1 Display Units: Min Range: 0-60 |
|
|
CHWP-MINONTIME, CWP-MINONTIME, PCHWP-MINONTIME, SCHWP-MINONTIME (Min On Time) |
Indicates the minimum amount of on time applied to all pumps. |
1 Display Units: Min Range: 0-60 |
|
|
CHWP BASE LOAD, CWP BASE LOAD, PCHWP BASE LOAD, SCHWP BASE LOAD (Minimum Flow) |
Indicates the minimum capacity (flow) that the system needs to maintain. Together with the Process Variable, this input defines the minimum number of pumps to command. It is assumed that other application block, presumably the Chiller Selector module, sets the two inputs according to the chillers flow requirements, setting both of them to zero only when no flow is necessary (for example, when pump down is finished). |
0 Display units come from Flow Units. |
|
|
Predicted Adjusted Efficiency |
SC, V |
Indicates the Predicted Efficiency of the Required Devices (steady state device commands) adjusted for run time imbalances, start count imbalances, start/stop differences, user-defined efficiency hysteresis, and start/stop efficiency penalty. |
0 Display Units: % |
|
Predicted Efficiency |
SC, V |
Indicates the expected capacity weighted efficiency based on the Required Devices (steady state device commands). |
0 Display Units: % |
|
Predicted Percent Load |
SC, V |
Indicates the expected percent load based on the Required Devices (steady state device commands). |
0 Display Units: % |
|
Process Variable |
Provides a value depending on the Control Mode property. When Control Mode is Constant Speed, the Process Variable is the Requested Flow. When Control Mode is Variable Speed, the Process Variable is the current commanded speed to all pumps. This value is calculated elsewhere in the application by a PID that controls the water pressure drop across the load. |
0 When Mode is Constant Speed, the Display units come from Process Variable Units. When Mode is Variable Speed, the display units is %. |
|
|
Process Variable Units |
Indicates the units used for the Process Variable depending on the Units of the application and the Mode of Operation. |
kW Set Name: Unit |
|
|
Required Devices |
SC, V |
Provides an integer output representing the packed bits of the desired steady state set of pumps commanded On.For example, a value of 4 means 1-0-0, which indicates pump 3 is On and pumps 2 and 1 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 pump 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 Control |
Enables Sequence Row parameter to enable devices. |
False |
|
|
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 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 |
|
|
Stabilize Time |
Indicates the amount of time to wait after a pump is commanded off or on before evaluating if the current combination of pumps is meeting the current demand, or if another pump should be turned on or off. This should reflect the amount of time it takes for a pump to ramp up its commanded speed, and the amount of time it takes for the system to recognize a change to the process variable. |
0 Display Units: Min |
|
|
Staging Margin |
When considering a downstage combination, the percent load actually increases by this value when performing the efficiency calculation. This method provides a safety margin as the percent load is a theoretical value, and the actual percent load of the new combination could be higher than calculated. When considering an upstage combination, the percent load actually reduces by this value when performing the efficiency calculation. This method provides a safety margin as the actual percent load of the new combination could be lower than calculated. Since the Upper Optimal Pct Load is typically closer to 100% than the Lower Optimal Pct Load is to 0%, the slope of the right hand side curve is much steeper than the left hand side slope; therefore, when the load is increasing, the system efficiency of the current combination drops faster compared with the slower increase of efficiency of the new combination, allowing the algorithm to switch to a new stage. |
2.0 Display Units: % Range: 0.0-10.0 |
|
|
System Enable |
Disables/enables the pump selector. When System Enabled is False, the Pump Selector downstages to zero capacity. |
False |
|
|
CHWP UPPER PCT LOAD, CWP UPPER PCT LOAD, PCHWP UPPER PCT LOAD, SCHWP UPPER PCT LOAD (Upper Optimal Pct Load) |
Indicates the nominal value that applies to all pumps collectively. This value is the right hand endpoint of the pump efficiency plateau. When this value increases, the application stages up at higher percent loads. For example, a plant runs pumps with a combined capacity of 400 gpm. When the Upper Percent Load is 80%, the application considers staging up when the current required flow exceeds 320 gpm. If this value is changed to 95, the application does not consider staging up until the required flow exceeds 380 gpm. |
98 Display Units: % Maximum Value: 99.9 |