Honeywell EXCEL 5000 User Manual page 158

ALPHABETIC REFERENCE
74-5577–33 (US)
EN2B-0184 GE51 R0518 (Europe)
Cool-Down Optimization WITH Room Sensor
Cool-down optimization with a room sensor operates with the same principles as
without a room sensor but it also takes into account room temperature:
• If the room temperature is higher than the setpoint (for example, through
isolation, body heat, etc), the characteristic set is steeper causing EOH to switch
off heating earlier (maximum 120 minutes).
• If room temperature is less than the setpoint, characteristic set is more gradual
causing EOH to leave the heating on longer (maximum time is until the switch
point set by the Time Program).
EOH calculates preheat time with room sensor (t VVR ) with the following formula:
Where t corr equals (X1 - X3) * P9, in other words, room temperature minus setpoint
times optimum stop factor.
If Parameter P9 is zero, the cool-down optimization procedure with room sensor is
the same as without a room sensor.
As an example, assume the following values:
Outdoor air temperature X2 = 42F (5.6C)
Minimum outdoor air temperature P7 = 32F (0C)
Factor for early switch-off P9 = 10 min/FDeg
Room temperature X1 = 70F (21.1C)
Target room temperature setpoint X3 = 68F (20C)
Advance preheat time with room sensor:
t VVR = 39 min (without a room sensor t VV = 36 min).
During this cool-down phase, EOH transmits a 1 to output YD3. This 1 overwrites
the supply temperature setpoint from the application program by the flow
temperature setpoint (Y1) from EOH.
At the end of the cool-down phase, EOH sets output YD3 to 0.
If room temperature X1 falls below the setpoint of the Time Program before the
target time occurs, EOH switches over to room control automatically. You must use
an internal PID controller which integral action time (P16) and room controller
multiplier (P15) can be set.
After reaching the target time, EOH still works with the supply temperature setpoint
from the heating curve. EOH set output YD2 to logical 0.
When preparing the Time Program, ensure that the switch point for cool-down is
always the latest possible time in the Time Program to avoid premature cool-down
and room temperatures outside the comfort zone.
Adaptation of Optimization
EOH calculates the times for the beginning of preheat and cool-down optimization in
advance. Because the time for optimized preheat varies from system to system
even with the same temperature conditions because of the behavior of the heating
system and the building, EOH maintains a "model" of the building. The dead time
and time constants for the building determine the dynamic behavior of the model.
EOH maintains two models for preheat because it is necessary to distinguish
between building characteristics after a short cool-down and after a lengthy cool-
down.
Dead time 1 (Parameter P10) and Time constant 1 (Parameter P11) define the first
model. This building model applies for a preheat that follows a short cool-down (less
than 24 hours).
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EXCEL CARE CONTROL ICONS