Attributes (Chiller Selector) - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 15.0

Controller Tool Help

Brand
Johnson Controls
Metasys
Product name
Controller Configuration Tool
Document type
User Guide
Document number
LIT-12011147
Version
15.0
Revision date
2022-11-18
Language
English

The following table describes the attributes used by the Chiller Selector modules:

Table 1. Chiller Selector Attributes

Name

Type 1

Description

Default Value

Available Capacity

V

Provides the sum of the derated capacities of the enabled devices.

0

Display units come from Capacity Units.

CHLR CAP LIMIT (Capacity Limit)

V

Limits the capacity of the devices currently on for a time to achieve a more stable transition when adding a device. This output is used in headered chilled water systems with variable speed chillers only.

You may set up the Capacity Limit feature in Manual or Automatic mode using the Capacity Limit Setup input:

  • Manual: When adding any device (including the first device), the Capacity Limit output is restricted to the Capacity Limit User Input for the Capacity Limit Hold Time, after which the output releases back to 100% (no limit).
  • Automatic: When adding the first device, the Capacity Limit output is not limited (100%). When adding any additional device, the Capacity Limit output ramps from 100% down to the Current Percent Load in half the Capacity Limit Hold Time. At the end of the Capacity Hold Time, the Capacity Limit output releases back to 100%.

100

Display Units: %

Range: 30-100

Capacity Limit Hold Time

 

Indicates the amount of time to restrict the output when Capacity Limit is active.

10

Display Units: Min

Minimum Value: 1

Maximum Value: Less than Stabilize Time

Capacity Limit Setup

 

Determines the Capacity Limit feature implementation. The options are Manual or Automatic.

Manual

Set Name: Reset Type

CHLR CURRENT LIMIT (Capacity Limit User Input)

 

Limits the total capacity of all devices currently on when the Capacity Limit Setup is Manual and Capacity Limit is active.

60

Display Units: %

Range: 30-100

Capacity Units

 

Indicates the units used for capacity depending on the Units of the application.

Tons

Set Name: Unit

CHW Available Flow

 

Indicates the chilled water flow available based on the pump enables and pump ratings (for headered CHW systems). Chiller combinations requiring a minimum headered chilled water flow greater than this value are not requested. This value is typically available from the CHW Pump Selector.

0

Display units come from Flow Units.

Minimum Value: 0

CHW Commanded Flow

 

Indicates the actual chilled water flow based on the pump status and pump ratings. This value is used in the percent load calculations for headered CHW systems only, and is typically available from the CHW Pump Selector. This value must be greater than CHW Min flow defined in the Device Info Table before the chiller can be commanded on.

0

Display units come from Flow Units.

Minimum Value: 0

CHW Headered/Dedicated

 

Specifies whether operating with headered, dedicated, or no pumping on the Chilled Water side of the chiller.

Headered

Set Name:

HeaderedDedicated

CHW Iso Valve/Pump nn Cmd

V

Provides the request commands to the chilled water side isolation valves or any dedicated pumps (where nn is 01-08). Headered pumps are not controlled by this module.

False

CHW Max Flow

 

Indicates the maximum chilled water flow of each device.

0

Display units come from Flow Units.

CHW Min Flow

 

Indicates the minimum chilled water flow of each device (in flow units).

0

Display units come from Flow Units.

CHW Temperature

 

Provides the Chilled Water Temperature input, which is used to calculate the instantaneous Uprated Capacity of the devices.

6.7 °C, 44 °F

Minimum: 18 °C, 0 °F

Maximum: 50 °C, 120 °F

CHLR COAST (Coast)

 

Allows the module to stage down when the load diminishes, by turning off devices (instead of switching to smaller devices) while preventing the module from staging up even if the load increases.

False

Control Mode

 

Determines how the process variable is treated:

  • 0) Building Load: The process variable is the building’s chilled water heat gain calculated elsewhere in the application. This load is compared with the current requested rated device capacity to call for more or less device capacity.
  • 1) Chiller Load: Similar to Building Load. The process variable is the sum of the amperage (or kW) currently consumed by the active devices and compared with the currently requested rated device current (or power).
  • 2) Flow Differential: This mode is for use with primary constant speed pumps only. In this arrangement, the process variable provides the signed differential flow (positive value indicates the flow in the primary loop is greater than the flow through the secondary loop, negative value indicates the flow in the primary loop is less than the flow through the secondary loop).

    When operating in this mode, the Chiller Selector module attempts to maintain the flow in the bypass close to zero that is when the plant capacity matches the building load.

  • 3) Temperature Differential: This mode is for use only with primary constant speed pumps with or without secondary pumps. The Process Variable is the Temperature drop across the chillers and is used to calculate the chiller plant load.

Building Load

Set Name: Chiller Control

 

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 COP

V

Indicates the capacity weighted efficiency (COP) of the devices currently commanded to On.

0.1

Display Units: %

Current Percent Load

V

Indicates the percent loading of the devices currently commanded to On adjusted by the Derate Percent.

0

Display Units: %

Current/Power Units

 

Indicates the units used for the current/power depending on the Units of the application.

A

Set Name: Unit

CW Available Flow

 

Indicates the condenser water flow available based on the pump enables and pump ratings (for headered CW systems). Chiller combinations requiring a minimum headered condenser water flow greater than this value are not requested. This value is typically available from the CW Pump Selector.

0

Display units come from Flow Units.

Minimum Value: 0

CW Commanded Flow

 

Indicates the actual condenser water flow based on the pump status and pump ratings. This value is used in the percent load calculations for headered CW systems only, and is typically available from the CW Pump Selector. This value must be greater than CW Min flow defined in the Device Info table before the chiller can be commanded on.

0

Display units come from Flow Units.

Minimum Value: 0

CW Headered/Dedicated

 

Specifies whether operating with headered, dedicated, or no pumping on the Condenser Water side of the chiller.

Headered

Set Name:

HeaderedDedicated

CW Iso Valve/Pump nn Cmd

V

Provides the request commands to the condenser water side isolation valves or any dedicated pumps (where nn is 01-08). Headered pumps are not controlled by this module.

False

CW Min Flow

 

Indicates the minimum condenser flow of each device (in flow units).

0

Display units come from Flow Units.

CW Temperature

 

Provides the Condenser Water Temperature input, which is used to calculate the instantaneous Uprated Capacity of the devices.

29.4 °C, 85 °F

Minimum: 2 °C, 35 °F

Maximum: 50 °C, 120 °F

Delta Temperature Units

 

Indicates the units used for temperature depending on the Units of the application.

delta °F

Set Name: Unit

Derate Now

 

Forces an upstage.

This input is used only when the Control Mode is Building Load, as possible device malfunction (for example, a fouled device or a day that is beyond the design day) may result in not meeting the building load, and the module is unable to determine a saturation condition from the input Process Variable or the calculated percent load. The module acts as it is meeting the cooling demand. Therefore, this input may force a necessary upstage.

False

Derate Reset

 

Resets the derating percent value to zero instantly rather than waiting for its inherent decay. The derate reset action is triggered at the rising edge of the module. See Derate Now.

False

Derating Percent

V

Indicates the percentage of derating internally applied to all devices. This value is calculated and used in Building Load Mode only. If devices are unable to meet the rated capacities, elsewhere in the application the Derate Now input is set to True. The Chiller Selector then derates the devices by this percentage. Large values of this property should be investigated since it could indicate possible malfunction of the chillers.

0

Display Units: %

Device Info

 

Provides a structure of arrays containing individual information of each device. This structure contains: Rated Capacity, CW Min Flow, Rated CW Flow, CHW Min Flow, Rated CHW Flow, Peak COP, Device Lift, Lift Sensitivity, Rated Current/Power, CHW Max Flow, Max Pct Load, Min Pct Load, Min Pct Load COP, Max Pct Load COP, Interstage Transition Delay, Stabilize Time.

 

Lift Sensitivity

 

Indicates the sensitivity of the device capacity to changes in the difference between the condenser and chilled water temperatures.

The Chiller Selector adjusts the capacity due to lift according to the following equation:

Ca = S * (La - Lr) + Cr

where:

  • S is the lift sensitivity
  • Ca is the adjusted capacity of the chiller at the reduced lift
  • Cr is the rated capacity of the chiller at the rated lift
  • La is the reduced lift
  • Lr is the rated lift

S is calculated as follows:

S = (Ca - Cr) / (La - Lr)

0.0

Units: kW, °C, Ton, °F

Device nn Cmd

V

Provides the lift request commands to each device (where nn is 01-08).

False

Device nn Current Power Out

V

Provides an output with the Rated Capacity used elsewhere in the application (where nn is 01-08).

0

Display units come from Capacity Units.

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).

Off

Set Name: Off/On

Device Type

 

Indicates the required letter for each device. If the types are all the same or it doesn’t matter, then use Type A for each. The default value is all devices Type A.

Type A

Set Name: Chiller Type

Flow Units

 

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 chiller 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.

0.005

Display Units: %

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

Interstage Transition Delay

 

When changing from one combination of devices to another, this is the amount of time to wait between turning one device on and another device off. For example: The system has three chillers, and chillers 1 and 3 are running, and the system requirements change such that it is more efficient to run chillers 1 and 2. This scenario requires two chillers to change and only one is allowed to change at a time. Therefore, the chiller selector turns on chiller 2, waits the interstage delay time, then turns off chiller 3.

8

Display Units: Min

Range: 1-120

Is Stable

SC, V

Specifies whether the Stabilize Timer has expired and the Process Variable can be used to update the combination of devices. The stabilize timer starts when a chiller command output or a chiller status input changes. A shorter stabilize timer (20% of the Stabilization Time) also starts when the Chilled Water Commanded Flow input changes due to the start or stop of a chilled water pump.

False

Iso Valve Stroke Time

 

Indicates the stroke time of the isolation valve. This input delays the process of turning the chilled water pump on and off. Since dedicated systems do not use this type of valve, the tool sets this property equal to zero during selection.

60

Display Units: Sec

Range: 0-180

CHLR LOWER PCT LOAD (Lower Optimal Pct Load)

 

Indicates the left hand endpoint of the chiller efficiency plateau. When the percent load goes below this value, the module considers other combinations of devices that would produce a higher percent load. This is a nominal value that applies to each device individually.

60

Display Units: %

The maximum value must be less than the Higher Optimal Pct Load value.

Minimum Value: 30

Low Load

 

Indicates the only operating chiller has been commanded off to provide chilled water more efficiently.

False

Max CHW Flow

 

Indicates the sum of the Rated CHW Max Flows of all the devices currently On. This is the maximum amount of variable speed CHW Flow that the chiller selector is allowing the Variable Speed Pump Selector to command.

0

Display units come from Flow Units.

Max Delta CHWT

 

Indicates the maximum temperature drop across all devices in selectable units. This value is used when the Control Mode is Temperature Differential. When the process variable (Temperature Differential) equals this value, the percent loading is 100%.

12

Display units come from Delta Temperature Units.

Min CHW Flow Setpoint

V

Indicates the minimum flow required for safe chiller operation. This output is used in headered variable speed chilled water systems.

0

Display units come from Flow Units.

Min CW Flow Setpoint

V

Indicates the minimum flow required for safe chiller operation. This output is used in headered variable speed condenser water systems.

0

Display units come from Flow Units.

CHLR-MINOFFTIME (Min Off Time)

 

Indicates the minimum amount of off time applied to all devices.

10

Display Units: Min

Range: 1-480

CHLR-MINONTIME (Min On Time)

 

Indicates the minimum amount of on time applied to all devices.

10

Display Units: Min

Range: 1-480

CHLR BASE LOAD (Min Required Capacity)

 

Indicates a value in units of load. The Chiller Selector module maintains, at a minimum, this amount of rated cooling. It is recommended to set this input to the desired chiller capacity times the optimal percent load (halfway between the lower and upper optimal percentages). For example, if the average of the Upper and Lower Optimal Load Percent is 80% and the minimum run conditions are two 70T chillers, the Min Required Capacity is (2 * 70) * 80% = 112T.

0.1

Display units come from Capacity Units.

The minimum value must be greater than 0.

Peak COP

 

Indicates the peak Coefficient of Performance (COP) of each device, which is the ratio of cooling output to power input. Combinations of devices that have higher peak COPs are preferentially selected during operation without regard for improving run time or start count imbalances.

Only devices with the same Peak COP have the ability to be balanced for run time and/or start counts. For example, if two devices have peak COPs X and two other devices have peak COPs Y, start count and runtime balancing occurs among the devices with peak COPs X and among the devices with peak COPs Y but not among all devices. This happens because the run time and start count adjustments are an order of magnitude more precise (to the hundredths place) than the precision of the Peak COPs (to the tenths place).

7.0

Minimum Value: 0.1

Display Units: %

Predicted Adjust COP

SC, V

Indicates the Predicted COP adjusted for runtime, start count, start/stop, load change, and hysteresis penalties.

0.1

Predicted COP

SC, V

Indicates the expected capacity weighted coefficient of performance (COP) based on the Required Devices (steady state device commands).

0.1

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 used to determine the current load of the chiller plant. See Control Mode.

0

Display units come from Process Variable Units.

When Mode is Building Load, Chiller Load, or Temperature Differential, the minimum value is 0.

Process Variable Units

 

Indicates the units used for the Process Variable depending on the Units of the application and the Mode of Operation. When the Mode is Chiller Load, an selection option is available in the System Selection wizard.

kW

Set Name: Unit

Pump Delay

 

Indicates the longest amount of time required for the pump to stop once a stop is received, or the amount of time to speed up once the on command is received.

15

Display Units: Sec

Range: 0-120

CHLR PMP DWN TIME (Pump Down Time)b

 

Indicates the amount of time to run the CW and CHW pumps after turning off a device. This delay allows the removal of refrigerant from the evaporator.

10

Display Units: Min

Range: 1-120

Rated Capacity

 

Indicates the cooling capacities of each device (in capacity units).

0

Display units come from Capacity Units.

Rated CHW Flow

 

Indicates the rated chilled water flow of each device (in flow units).

0

Display units come from Flow Units.

Rated CHW Max Flow

 

Indicates the rated maximum flow of each device (in flow units).

0

Display units come from Flow Units.

Rated Current Power

 

Indicates the rated current of each device.

0

Display units come from Current/Power Units.

Rated CW Flow

 

Indicates the rated condenser flow of each device (in flow units).

0

Display units come from Flow Units.

Required CHW Flow

V

Indicates the required chilled water flow associated with the currently requested (or soon to be requested) devices. This output is used in headered chilled water systems.

To ensure enough chilled water flow during chiller staging, the CHW Required Flow is increased by 10% with a minimum value as calculated and a maximum value equal to the Rated CHW Flow.

This flow requirement value is issued with enough anticipation to allow flows to be obtained prior to devices turning on and maintains its high value while the Pump Down Timer is active, when devices are being turned off.

0

Display units come from Flow Units.

Required CW Flow

V

Indicates the required condenser water flow associated with the currently requested (or soon to be requested) devices. This output is used in headered condenser water systems.

The module calculates a minimum condenser water flow based on the individual minimum condenser water requirements and the rated condenser water flows.

To ensure enough condenser water flow during chiller staging, the CW Required Flow is increased by 10% with a minimum value as calculated and a maximum value equal to the Rated CW Flow.

This flow requirement value is issued with enough anticipation to allow flows to be obtained prior to devices turning on and maintains its high value while the Pump Down Timer is active, when devices are being turned off.

0

Display units come from Flow Units.

Required Devices

SC, V

Provides an integer output representing the packed bits of the desired steady state set of devices commanded On.

For example, a value of 88 means 0-1-0-1-1-0-0-0, which indicates device 2, 4, and 5 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 chiller selector moves toward the desired steady state.

0

Required Tower Flow

V

Indicates the required cooling tower water flow. This output is a time-shifted version of the Required CW Flow output to ensure proper sequencing of the cooling tower with the other equipment when devices are added or removed. This is the sum of the chiller rated flow sent to the cooling tower selector.

0

Display units come from Flow Units.

Rotate Now

 

On the rising edge of this signal, the Chiller Selector calculates a new combination of devices that provides the required cooling capacity while promoting the maximum rotation of the chillers.

False

Rotation Mode

 

Determines how rotation is processed:

  • 0: None. The module does not attempt to equalize either runtimes or start counts of the individual devices.
  • 1: Run Time. The module attempts to equalize the runtimes of the individual devices.
  • 2: Start Counts. The module attempts to equalize the start counts of the individual devices.
  • 3: Both. The module attempts to equalize both start counts and run times of the individual devices.

None

Set Name: Rotation Mode

Sequence Row

 

Indicates a 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 Table

 

Provides an array of integers. Each column is a device type letter (maximum of letter types above). Each row is a combination represented by counts of each device type.

 

Stabilize Time

 

Indicates the amount of time after a device changes on or off that the must elapse before recognizing changes to the Process Variable.

15

Display Units: Min

Range: 15-120

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: %

Steady Sequence Row

SC, V

Indicates the row of the sequence table that the module is moving towards. If the Sequence Table is not defined, this value is zero.

 

System Enable

 

Disables/enables the chiller plant. When System Enabled is False, the Chiller Selector downstages to zero capacity.

False

CHLR START DELAY (System Start Delay)b

 

Indicates the delay applied when the System Enabled input transitions from Disabled to Enabled. The Minimum Load is maintained during this time allowing the chilled and condenser water pumps to operate.

This time period is typically longer than the Stabilize Time to allow the system to achieve steady state after not being under control for some time.

30

Display Units: Min

Time Constant

 

Indicates the amount of time required for a first-order system to reach 63% of its final magnitude, given a 100% step change of its process variable. The Period of execution of the module is Time Constant divided by 6.

500

Display Units: Sec

Range: 60-3,600

Total Current/Power

V

Indicates the total actual current/power output of all currently operating devices.

0

Display units come from Current/Power Units.

Tower Available Flow

 

Indicates the available cooling tower flow based on tower enabled and its capacity. The Chiller Selector uses this value in determining valid device combinations. The value is typically available from the Cooling Tower Selector.

0

Minimum Value: 0

Display units come from Flow Units.

Tower Commanded Flow

 

Indicates the Cooling Tower flow based on Cooling Tower status and its capacity. This value must be greater than the CW Min flow defined in the Device Info Table before the chiller can be commanded on. This value provides status feedback to the Chiller Selector to ensure proper sequencing of the cooling tower with the other equipment when a device is added or removed. The value is typically available from the Cooling Tower Selector.

0

Minimum Value: 0

Display units come from Flow Units.

Tower Piping

 

Specifies whether operating with headered, dedicated, or no cooling tower piping on the Condenser Water side of the chiller.

Headered

Set Name:

HeaderedDedicated

CHLRx-UPPER PCT LOAD (Upper Optimal Pct Load)

 

Indicates the right hand endpoint of the chiller efficiency plateau. When the percent load goes above this value, the module considers other combinations of devices that would produce a lower percent load. This is a nominal value that applies to the device individually.

90

Display Units: %

The minimum value must be greater than the Lower Optimal Pct Load value.

Maximum Value: 100

1 C - Configuration Mode Only, G - Default Element (Generated State, if applicable), SC - Simulation and Commissioning Modes Only, V - Calculated Value (Outputs)