Honeywell EXCEL 5000 User Manual page 155

EXCEL CARE CONTROL ICONS
program again apply. EOH calculates the supply temperature setpoint (Y1) in
accordance with the heating curve. Parameter P18 provides the curvature.
Parameter P19 provides the slope which is displaced in accordance with the room
temperature setpoint including the increase. See the HCA Icon section for further
explanations of the heating curve.
Cool-Down Optimization WITHOUT Room Sensor
In cool-down optimization, EOH only looks at the outdoor air temperature to define
the time point for early setback. The maximum advance of the switch-off point is 2
hours. EOH advances the switch-off point of the Time Program by this time interval
when the momentary outdoor air temperature (X2) corresponds exactly to the room
temperature setpoint of the Time Program (X3). If outdoor air temperature is less
than the limit defined by Parameter P7, no early switch-off occurs. Between these
two points, EOH uses the following linear interpolation to advance switch-off point
t VV :
t VV = 120 min * (X2 - P7) / (X3 - P7)
The following diagram illustrates this action:
As an example, given the following values:
Outdoor air temperature X2 = 43F (6C)
Minimum outdoor air temperature P7 = 32F (0C)
Momentary room temperature setpoint X3 (Time Program value) = 68F (20C)
t VV = 120 min * (6 - 0) / (20 - 0)
t VV = 36 min
During this total setback phase, EOH transmits a 1 to output YD3. This value
overwrites the supply temperature setpoint from the normal application program by
flow temperature setpoint (Y1) from EOH.
CAUTION
During the total setback phase, EOH transmits a supply temperature demand
of 32F (0C) to Y1. You must implement any freeze protection functions
required for the total setback phase outside of EOH.
After the cool-down phase, EOH resets output YD3 to zero so that the normal
application program is again in control.
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ALPHABETIC REFERENCE
74-5577–33 (US)
EN2B-0184 GE51 R0518 (Europe)