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Appendix A: RTU Open Points/Properties
Point Name/Description
Heating Capacity
– Used for Optimal Start, this is the rate at which the zone temperature
changes when the heating system runs at full capacity to maintain designed occupied heating
setpoint.
Heating Design Temp
– The geographically-based outdoor air temperature at which the heating
system must run constantly to maintain comfort. This information is available in ASHRAE
publications and most design references.
Cooling Capacity
– Used for Optimal Start, this is the rate at which the zone temperature
changes when cooling system runs at full capacity to maintain designed occupied cooling
setpoint.
Cooling Design Temp
– The geographically-based outdoor air temperature at which the cooling
system must run constantly to maintain comfort. This information is available in ASHRAE
publications and most design references.
Hysteresis
– The desired difference between the temperature at which the zone color changes
as the zone temperature departs from the acceptable range between the heating and cooling
setpoints (green) into the Cooling 1 (yellow) or Heating 1 (light blue) and the temperature at
which the zone color changes back to the acceptable range between the heating and cooling
setpoints.
For example, the following graph shows the zone color that results as the zone temperature
departs from and returns to the acceptable range in a zone with the following settings:
•
Color Change Hysteresis = .5° (applies as the temperature returns to the acceptable
range)
•
Occupied cooling setpoint = 76°
•
Occupied heating setpoint = 70°
Temp
Occupied cooling setpoint: 76°
75.5°
70.5°
Occupied heating setpoint: 70°
Effective Setpoints
The Effective Setpoints graph shows the current occupied or unoccupied setpoints. If occupied, these values are the current
programmed setpoints plus the offset of any setpoint adjustment that may be in affect. If unoccupied, the values are the
programmed unoccupied setpoints.
64
.5° hysteresis
.5° hysteresis
Time
Default/Range
D:
5°F/hr
R:
0 to 120°F/hr
D:
0°F
R:
-100 to 150°F
D:
5°F/hr
R:
0 to 140°F/hr
D:
100°F
R:
-100 to 150°F
D:
0.5°F
R:
0 to 120°F
RTU Open
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