TEC Zoning Control System for Stand-Alone and BACnet® MS/TP ...
TEC Zoning Control System for Stand-Alone and BACnet® MS/TP ...
TEC Zoning Control System for Stand-Alone and BACnet® MS/TP ...
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It is possible to adjust the system to completely eliminate heating <strong>and</strong> coolingequipment cycling based on the outside air limitations, if this type of systemoperation is desired. Figure 6 illustrates two ways to eliminate overlappingdeadb<strong>and</strong> <strong>and</strong> the associated equipment cycling. Note that eliminating overlappingdeadb<strong>and</strong> may impact the control per<strong>for</strong>mance of certain zones during otherperiods of system operation.Heating Lockout =72°F (22°C)No Overlapping Deadb<strong>and</strong>Cooling Lockout =72°F (22°C)Outside Air TemperatureHeating Lockout =70°F (21°C)5F° (3C°)Deadb<strong>and</strong>;No Heating<strong>and</strong>No CoolingCooling Lockout =75°F (24°C)FIG:no_ovrlppng_ddbndOutside Air TemperatureFigure 6: No Overlapping Deadb<strong>and</strong>Seasonal ChangeoverHeating <strong>and</strong> cooling equipment cycling during seasonal changeover is almostinevitable with a VAV zoning control system, if any degree of occupancy com<strong>for</strong>tis to be maintained. A properly set up system delivers com<strong>for</strong>t to conflicting zonedem<strong>and</strong>s during seasonal changeover by alternating between heating <strong>and</strong> coolingat the rooftop controller.Unwanted heating <strong>and</strong> cooling switchovers are eliminated by either using <strong>and</strong>authorizing terminal reheat, or by limiting the rooftop controller heating <strong>and</strong>cooling capacity throughput based on the outside air temperature (H lock <strong>and</strong>C lock parameters). Note that limiting the rooftop controller heating <strong>and</strong> coolingcapacity throughput based on the outside air temperature may impact the controlper<strong>for</strong>mance of certain zones in the system, since the required heating or coolingcapacity is no longer available due to the lockout conditions.40<strong>TEC</strong> <strong>Zoning</strong> <strong>Control</strong> <strong>System</strong> <strong>for</strong> <strong>St<strong>and</strong></strong>-<strong>Alone</strong> <strong>and</strong> <strong>BACnet®</strong> <strong>MS</strong>/<strong>TP</strong> Networked ApplicationsTechnical Bulletin