Controls
This tab displays the controls that have been added to the loop form the Controls and sensors category of the Plant Component Selection Bar. These control strategies allow for the equipment to follow certain set point temperatures. Each control added on the Plant diagram will display its required input fields depending on the loop type it is assigned to and the following Control Strategy options.
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Schedule
This controller allows you to enter a set point temperature either as a constant or through a pre-created schedule. The required fields will vary slightly depending on the selected Set point type.
Applicable Loops - Chilled Water, Hot Water, Condenser and all Heat Exchanger loops except Mixed Water to Hot Water and Mixed Water to Chilled Water.
Set point Control Type
The two options are Constant and Variable. Constant will maintain the same value during the whole simulation period. Variable requires the definition of a schedule that defines the set point value for different time periods.
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Default value: N/A
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Min & Max: N/A
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Typical Range: N/A
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Units: N/A
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Constant Control Set point
This is the set point temperature to which the equipment is controlling to. This may be similar or same as the design leaving temperature. This field is only available when “Constant” is selected for the Set point Control Type.
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Default value: Cooling: 44°F; 6°C, Heating: 180°F; 82°C, Condenser 85°F; 30°C
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Min & Max: 0 to 999°F
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Typical Range: 40 to 999°F
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Units: °F; °C
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Variable Control Schedule
Here a schedule can be applied to determine at what specific hours a piece of equipment needs to meet a certain set point condition. This field is only available when “Variable” is selected for the Set point Control Type. See Temperature Setpoint Schedules for more information on how to create the schedule.
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Default value: N/A
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Min & Max: N/A
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Typical Range: N/A
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Units: N/A
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Water Reset based on OA
The Outdoor Air Reset Set point Manager sets the supplied water temperature according to the outdoor air temperature using a reset rule. The reset rule is determined by 2 points: the water set point temperature at the outdoor high temperature (SATOH) and the water set point temperature at the outdoor low temperature (SATOL). If the outdoor temperature is above the outdoor high temperature, the water temperature is set to SATOH. If the outdoor temperature is below the outdoor low temperature, the water temperature is set to SATOL. If the outdoor temperature is between the outdoor high and outdoor low temperatures, the water temperature is linearly interpolated between SATOH and SATOL.
Applicable Loops - Chilled Water, Hot Water, Condenser and all Heat Exchanger loops except Mixed Water to Hot Water and Mixed Water to Chilled Water.
The required fields are:
Outdoor Air Reset
Here a schedule can be applied to determine at what specific hours a piece of equipment needs to meet a certain set point condition and when the temperature is reset based on the OA condition. See Outdoor Air Reset Schedules for more information on how to create the schedule.
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Default value: N/A
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Min & Max: N/A
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Typical Range: N/A
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Units: N/A
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Follow OA temperature
This set point manager is used to place a temperature set point that is derived from the current outdoor air environmental conditions. The outdoor air conditions are obtained from the weather information during the simulation.
Applicable Loops - Chilled Water, Hot Water, Condenser and all Heat Exchanger loops except Mixed Water to Hot Water and Mixed Water to Chilled Water.
The required input fields are:
Reference Temperature Type
The reference temperature type is the type of temperature value that the supplied water temperature will follow. The choice is either Outdoor Dry Bulb Temperature or Outdoor Wet Bulb Temperature.
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Default value: Outdoor Air Wet Bulb
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Min & Max: N/A
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Typical Range: N/A
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Units: N/A
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Offset Temperature Difference
This field provides a temperature offset that will be applied to the value of the reference temperature (outdoor air wet bulb/dry bulb). If this value is zero, and the limits are met, then the resulting set point will be exactly the same as the outdoor air wet bulb/dry bulb temperature.
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Default value: 10°F
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Min & Max: -999 to 999
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Typical Range: 0 to 10
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Units: °F; °C
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Maximum Limit Setpoint Temperature
This field provides an upper limit to the resulting set point value.
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Default value: From template, Cooling: 54°F, 12°C; Condenser: 95°F, 35°C; Heating: 180°F, 82°C
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Min & Max: -999 to 999
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Typical Range: 20 to 100
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Units: °F; °C
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Minimum Limit Setpoint Temperature
This field provides a lower limit to the resulting set point value.
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Default value: From template, Cooling: 44°F, 6.6°C; Condenser: 55°F, 13°C; Heating: 120°F, 49°C
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Min & Max: -999 to 999
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Typical Range: 60 to 200
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Units: °F; °C
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Dual Setpoint
This controller is available in Mixed Water Loops. It will allow for two set point conditions in the loop – high and low. The temperature of the water loop will float in between these values and either a boiler or cooling tower will be used to maintain the set points at their respective conditions.
Applicable Loops – Mixed Water loops, Mixed Water to Hot Water Heat Exchanger loop and Mixed Water to Chilled Water Heat Exchanger loop.
The required input fields are:
Setpoint Control Type
The choices for this input are either “Variable” or “Constant”. Variable allows to a variation in controlling temperatures throughout the day whereas constant is a fixed temperature throughout the day.
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Default value: Constant
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Min & Max: N/A
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Typical Range: N/A
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Units: N/A
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Constant Control Low Set point
This field provides a lower limit to the set point condition. This is only available when the set point type is selected as Constant.
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Default value: 60°F
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Min & Max: -999 to 999
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Typical Range: 20 to 100
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Units: °F; °C
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Constant Control High Set point
This field provides a high limit to the set point condition. This is only available when the set point type is selected as Constant.
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Default value: 90°F
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Min & Max: -999 to 999
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Typical Range: 20 to 100
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Units: °F; °C
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Variable Control Low Setpoint
Here a schedule can be applied to determine at what specific hours a piece of equipment needs to meet the low set point water temperature condition. See Temperature Setpoint Schedules for more information on how to create the schedule.
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Default value: N/A
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Min & Max: N/A
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Typical Range: N/A
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Units: N/A
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Variable Control High Setpoint
Here a schedule can be applied to determine at what specific hours a piece of equipment needs to meet the high set point water temperature condition. See Temperature Setpoint Schedules for more information on how to create the schedule.
Follow Ground Temperature
This controller is used to place a temperature set point that is derived from a current ground temperature. Vertical bore heat exchangers and horizontal bore heat exchanger use deep ground temperature (Site Temperature at Depth). Pond heat exchanger uses shallow depth ground temperatures (Shallow Site Temperature).
Applicable Loops – Condenser loop.
Reference Temperature Type
The reference temperature type is the type of temperature value that the supplied water temperature will follow. The choice is either Leaving Component Dry Bulb Temperature or Leaving Component Wet Bulb Temperature.
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Default value: N/A
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Min & Max: N/A
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Typical Range: N/A
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Units: N/A
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Offset Temperature Difference
This field provides a temperature offset that will be applied to the value of the reference ground temperature. If this value is zero, and the limits are met, then the resulting set point will be exactly the same as the ground temperature.
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Default value: From template
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Min & Max: -999 to 999
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Typical Range: 0 to 10
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Units: °F; °C
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Maximum Limit Setpoint Temperature
This field provides an upper limit to the resulting set point value.
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Default value: From template
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Min & Max: -999 to 999
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Typical Range: 20 to 100
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Units: °F; °C
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Minimum Limit Setpoint Temperature
This field provides a lower limit to the resulting set point value.
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Default value: From template
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Min & Max: -999 to 999
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Typical Range: 60 to 200
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Units: °F; °C
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Optimized Tower
The optimized cooling tower control for water-cooled chillers resets the leaving tower water temperature (the condenser water loop temperature entering the building) to minimize the sum of chiller plus tower energy each hour. Without optimization controls (fixed set point), the cooling tower will attempt to reach the set point condition, if possible, because the compressor is more efficient at lower condenser operating temperatures. However, there is a trade-off since lowering the tower leaving temperature normally increases the tower energy consumption (unless the tower is also given a more efficient unloading curve). The chiller-tower optimizing algorithm balances the trade-off so the net energy (chiller plus tower) is less than the non-optimized solution. In optimized mode, the tower leaving temperature need not be reset to its lowest design setting, and will often be higher than the non-optimized tower control. The optimum tower leaving temperature is calculated to minimize the total energy consumption of the cooling tower and chiller, using rated tower, performance data, rated chiller performance data, the hourly load, and the outdoor air wet bulb temperature that hour. Note: For water-cooled chillers, optimization is only supported for centrifugal, helical rotary and screw compressor types.
Applicable Loops – Condenser loop, Condenser to Chilled Water Heat Exchanger loop and Condenser to Mixed Water Heat Exchanger loop.
Condenser Entering Water Temperature
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Default value: N/A
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Min & Max: -999 to 999
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Typical Range: 60 to 200
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Units: °F; °C
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Use System Defaults
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Default value: N/A
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Min & Max: -999 to 999
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Typical Range: 60 to 200
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Units: °F; °C
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Minimum Lift
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Default value: N/A
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Min & Max: -999 to 999
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Typical Range: 60 to 200
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Units: °F; °C
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Maximum Condenser Entering Water Temperature
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Default value: N/A
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Min & Max: -999 to 999
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Typical Range: 60 to 200
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Units: °F; °C
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Cooling Tower Design Inlet Air Wet-Bulb Temperature
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Default value: N/A
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Min & Max: -999 to 999
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Typical Range: 60 to 200
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Units: °F; °C
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Follow Return Temperature
This controller is used to place a temperature set point that is derived from the current loop return temperature.
Applicable Loops - Chilled Water, Hot Water, Condenser and all Heat Exchanger loops except Mixed Water to Hot Water and Mixed Water to Chilled Water.
Return Setpoint Control Type
The choices for this input are either “Variable” or “Constant”. Variable allows to a variation in controlling temperatures throughout the day whereas constant is a fixed temperature throughout the day.
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Default value: N/A
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Min & Max: N/A
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Typical Range: N/A
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Units: N/A
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Return Variable Control Setpoint
A schedule allow you to define variable setpoints. See Temperature Setpoint Schedules for more information on how to create the schedule.
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Default value: N/A
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Min & Max: -999 to 999
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Typical Range: 0 to 10
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Units: °F; °C
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Maximum Limit Setpoint Temperature
This field provides an upper limit to the resulting set point value.
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Default value: From template
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Min & Max: -999 to 999
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Typical Range: 20 to 100
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Units: °F; °C
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Minimum Limit Setpoint Temperature
This field provides a lower limit to the resulting set point value.
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Default value: From template
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Min & Max: -999 to 999
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Typical Range: 60 to 200
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Units: °F; °C
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