Zone Setpoint with Demand
 Control microblock
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The Zone Setpoint with Demand microblock calculates effective setpoints and zone colors for single zone equipment.
You can determine a zone's setpoints for both occupied and unoccupied periods; however, because of factors such as local overrides, demand level, or optimal start routines, the zone's effective setpoints may be calculated differently by the microblock. The color generated by the microblock represents the status of the control program to WebCTRL and can be used by other microblocks in the control program (such as the If Color = microblock) to perform additional control.
NOTE Do not use the Zone Setpoint with Demand microblock in combination with the Set Color or Set Color If True microblocks in the same control program. There cannot be more than one Zone Setpoint microblock in a control program.
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Properties
Property
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Notes
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occ
for
dem
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The microblock's occ, for, and dem inputs provide information used during Learning Adaptive Optimal Start. The dem input indicates the current electrical demand level (obtained from a Read Analog Property microblock). The occ input indicates whether or not the zone is currently occupied, and the for input indicates the amount of time remaining until the occupancy status changes.
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Occupancy
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Occupancy is normally determined by a BACnet Time Clock or BACnet Time Clock with TLO. If some other method is used to determine occupancy, attach a Binary Status microblock to the wire that leads into the Zone Setpoint's occ input.
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zone input
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The zone input receives the current zone temperature. The color broadcast by the microblock is based on the zone temperature in relation to the effective setpoints. The ht and cl outputs on the microblock contain the effective heating and cooling setpoints, respectively.
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Design Temperature
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The Design Temp section of the microblock dialog indicates the extreme outside temperatures at which equipment must run constantly in order to maintain comfort. Design temperatures are based on the geographic area of the building and are available from ASHRAE publications and most design references. On the Properties page, use the Heating Design Temp and Cooling Design Temp settings to change these values.
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Capacity
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The Capacity section of the microblock dialog indicates the maximum rate (in °F per hour) at which the heating and cooling equipment can change the temperature if the outside air temperature is 65°F. The accuracy of these values affects the ability of the equipment to bring the zone temperature to the occupied setpoint exactly at occupancy time, rather than too early or too late. On the Properties page, use the Heating Capacity and Cooling Capacity settings to change these values.
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RefName
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Use the default reference name unless you want a more descriptive name for this microblock for graphics, source tree rules, or network links. All reference names in a control program must be unique.
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Colored Band Settings on Microblock Dialog
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In the microblock dialog box, the settings on the colored bands determine the width (in degrees) of the colored bands on the Setpoint graph in WebCTRL for each level of electrical demand (0, 1, 2, or 3). The occupied band represents demand level zero. For each increase in the level of demand, you can offset the width of the color bands on the Setpoint graph by the number of degrees indicated on the appropriate band. Actual occupied and unoccupied setpoint values can be entered in the heating setpt and cooling setpt fields beneath the graph (the Heating and Cooling settings on the Properties page). When the zone is occupied, these values, adjusted for demand level, are the effective setpoints. When the zone is unoccupied, the microblock calculates effective setpoints using the Optimal Start routine. For example, set the dem1 band's cooling offset to 1.00, and the occupied cooling setpoint to 76.00. When the building is occupied and operating under demand level 1, the effective cooling setpoint is then 77.00. This effective setpoint is further adjusted by the value of the microblock's cadj input. This strategy allows the total building demand to be lowered, often without shutting off any equipment.
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Band Settings
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On the Properties page, the Bands settings determine the width of the color bands on the Setpoint graph. The Free setting determines the width of the green band (which allows free cooling from the outside air dampers when appropriate). If free cooling is not available, this property should be set to 0.00. The Stg1 setting determines the width of the yellow band for cooling and the light blue band for heating, and the Stg2 setting determines the width of the orange band for cooling and the dark blue band for heating. These settings for Free, Stg1 and Stg2 are used when the demand level is zero. The Offset settings allow you to enter an amount (in degrees) by which the Free, Stg1, and Stg2 settings will be adjusted for each level of demand.
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Color Change Hysteresis
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The Color Change Hysteresis is represented by the Hyst setting on the Properties page. When returning to normal, it is the number of degrees required to exceed the setpoint before the microblock's color changes. An appropriate hysteresis prevents equipment from "chattering" when the temperature is very close to and oscillating around the setpoint.
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Editing Privilege
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Preset (the default Editing Privilege) indicates that each property in a microblock has an appropriate privilege assigned to it.
If you change the Editing Privilege, all the properties in that microblock are assigned to that one editing privilege, which is not always desirable.
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NOTE Alt+click any value in WebCTRL to view property details, including its expression and editing privilege.
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