Availability Manager
The Availability Manager tab contains information on high temperature turn on, high temperature turn off, low temperature turn off, low temperature turn on, night purge, schedule, fan cycling, and optimum start.
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Schedule
Systems can be controlled to run based on an on/off schedule or based on occupancy.
Fan Cycling based on Occupancy/Schedule
The fans can be cycled on and off based on a simple schedule or based on the occupancy of a single zone or all the zones on the system.
Scheduled
The schedule can be chosen from the schedules library.
Cycle with occupancy in controlled zone
Fans will remain on when a particular zone is occupied and will cycle on and off when that zone is unoccupied. Note, the control zone can only be selected in the project, not in the library.
Cycle with occupancy based on all zones
Fans will remain on when any zone on the system is occupied and will cycle on and off when all zones on the system are unoccupied.
Optimum Start
The optimum start availability manager allows the heating and cooling equipment to start operating before the building becomes occupied so that by the time the building becomes occupied, the building is no longer at the drift point temperature but has been brought to the set point temperature for occupant comfort.
Schedule
The schedule defines during which hours this availability manager may be applied.
Control Type
Optimum Start Based on Control Zone: The optimum start controls will be controlled to one specific zone. This field is only available in the project and only after zones have been assigned to the system. Note, in the project this field will be shown even before zones have been assigned but cannot be edited until after zones have been assigned to the system. By default, the first zone assigned to the system will be set as the control zone but any zone assigned to the system can be selected from this dropdown.
Optimum Start based on fan schedule: This control will turn on the system based on the fan schedule.
Optimum Start Based on All Zones: The control will look at all the zones on the system and determine the earliest time that the equipment needs to start to serve all zones.
Maximum Value for Optimum Start Time
Default: 6 hours
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Min Max: - infinity to infinity
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Units: hours
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The start time can be limited to a certain number of hours before the building becomes occupied.
Control Algorithm
Constant Temperature Gradient: The temperature gradient entered by the user will be held constant throughout the year.
Adaptive Temperature Gradient: The temperature gradient will be modified throughout the year based on an average of the actual temperature gradient for a number of days before the currently calculated day.
Constant Start Time: The equipment will start at the same time every day.
Constant Temperature Gradient - Cooling
Default: blank
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Typical Range: 75 to 140°F; 24 to 60°C
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Min Max: - infinity to infinity
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Units: delta °F/hr; delta °C/hr
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This field is used if the Control Algorithm is set to Constant Temperature Gradient. This entered temperature gradient will be held constant throughout the year.
Constant Temperature Gradient - Heating
Default: blank
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Min Max: - infinity to infinity
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Units: delta °F/hr; delta °C/hr
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This field is used if the Control Algorithm is set to Constant Temperature Gradient. This entered temperature gradient will be held constant throughout the year.
Initial Temperature Gradient - Cooling
Default: blank
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Min Max: - infinity to infinity
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Units: delta °F/hr; delta °C/hr
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This field is used if the Control Algorithm is set to Adaptive Temperature Gradient. This value is used as an initial guess but according to the Adaptive Temperature Gradient, this value will change throughout the year.
Initial Temperature Gradient - Heating
Default: blank
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Min Max: - infinity to infinity
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Units: delta °F/hr; delta °C/hr
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This field is used if the Control Algorithm is set to Adaptive Temperature Gradient. This value is used as an initial guess but according to the Adaptive Temperature Gradient, this value will change throughout the year.
Constant Start Time
Default: blank
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Min Max: - infinity to infinity
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Units: hour
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This field is used if the Control Algorithm is set to Constant Start Time. This is the number of hours before occupancy that the equipment will start. The equipment will start at the same time each day.
Number of Previous Days
Default: 0
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Typical Range: 2 days to 5 days
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Min Max: 2 days to 5 days
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Units: days
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This field is used if the Control Algorithm is set to Adaptive Temperature Gradient. This value is the number of previous days that are averaged in order to calculate the temperature gradient for the currently calculated day.
High temperature turn on
Above this temperature, the system will turn on.
Sensor Location
This is the location in the system where the temperature sensor is located and the local temperature is compared to the high temperature turn on value.
High Temperature
Default: blank
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Typical Range: N/A
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Min Max: - infinity to infinity
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Units: °F; °C
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High temperature turn off
Below this temperature the system will turn off.
Sensor Location
This is the location in the system where the temperature sensor is located and the local temperature is compared to the high temperature turn off value.
High Temperature
Default: blank
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Typical Range: N/A
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Min Max: - infinity to infinity
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Units: °F; °C
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Low temperature turn on
Below this temperature the system will turn on.
Sensor Location
This is the location in the system where the temperature sensor is located and the local temperature is compared to the low temperature turn on value.
Low Temperature
Default: blank
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Typical Range: N/A
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Min Max: - infinity to infinity
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Units: °F; °C
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Low temperature turn off
Above this temperature the system will turn off.
Sensor Location
This is the location in the system where the temperature sensor is located and the local temperature is compared to the low temperature turn off value.
Low Temperature
Default: blank
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Typical Range: N/A
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Min Max: - infinity to infinity
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Units: °F; °C
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Night Purge
This control is used to precool the building during unoccupied hours by increasing the outdoor airflow.
Schedule
The schedule defines during which hours night purge may be applied.
Ventilation Maximum Limit Type
If the ventilation maximum limit type is set to constant, then the ventilation maximum limit will be a single temperature. If this is set to variable, then the ventilation maximum limit will vary throughout the day based on a schedule.
Ventilation Maximum Limit
This field defines either the ventilation maximum temperature if the limit type is set to constant or the ventilation maximum schedule if the limit type is set to variable.
Ventilation Temperature Difference
Default: 2°F
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Typical Range: N/A
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Min Max: - infinity to infinity
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Units: °F; °C
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This is the difference between the indoor and outdoor temperature above which night purge can occur. If the difference between the indoor and outdoor temperature is lower than this value, the night purge will turn off.
Ventilation Minimum Limit
Default: 15°F
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Typical Range: N/A
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Min Max: - infinity to infinity
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Units: °F; °C
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If any zone on this system is at a temperature lower than the ventilation temperature low limit, night purge will be turned off.
Ventilation Flow
Default: 1
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: dimensionless
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This is the fraction of the design supply airflow that can be admitted as outside air during night purge. This can be greater than 1.
Control Zone Name
This is the zone used to compare the indoor air temperature to the outdoor air temperature to calculate the ventilation temperature difference. This field is only available in the project and only after zones have been assigned to the system. Note, in the project this field will be shown even before zones have been assigned but cannot be edited until after zones have been assigned to the system. By default, the first zone assigned to the system will be set as the control zone but any zone assigned to the system can be selected from this dropdown.
Fan Performance Modifier
This allows the fan to use different performance parameters when running in night purge mode.
Fan Cycling
This availability manager defines the conditions under which the fans will cycle. Note, to cycle the fans based on occupancy, go to the Schedule tab of the Availability Manager properties and select Cycle with occupancy in control zone or Cycle with occupancy based on all zones from the dropdown.
Schedule
The schedule defines during which hours this fan cycling may be applied.
Control Type
● No Fan Cycling: This availability manager will have no affect and the fans will follow the operation dictated by the fan schedule.
● Cycle with all loads: The system will cycle on if any of the spaces on the system are outside the temperature setpoints.
● Cycle with loads in controlled zone: The system will cycle on only if a particular zone on the system is outside the temperature setpoints.
● Cycle with zone fans on load: The zone fans (not system fans) will cycle on if any of the spaces on the system are outside the temperature setpoints.
● Cycle with cooling load: The system will cycle on if any of the spaces on the system are outside the cooling temperature setpoint.
● Cycle with heating load: The system will cycle on if any of the spaces on the system are outside the heating temperature setpoint.
● Cycle zone fans on heating load: The zone fans (not system fans) will cycle on if any of the spaces on the system are outside of the heating temperature setpoint.
Thermostat Tolerance
Default: 1°F
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Typical Range: N/A
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Min Max: - infinity to infinity
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Units: °F; °C
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This is the number of degrees outside the temperature set points at which the system will cycle on.
Cycling Run Time
Default: 3600 seconds
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Typical Range: N/A
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Min Max: - infinity to infinity
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Units: seconds
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This is the number of seconds that the system will run after it has cycled on.