Honeywell EXCEL 5000 User Manual page 175

EXCEL CARE CONTROL ICONS
To allow an optimum stop to save a significant amount of energy without losing
comfort, the room temperature can drop by P7 below the actual room temperature
setpoint TSet – P7. In this moment the EOH3 switches to room control mode with
the room temperature setpoint equal to actual TSet – P7 and keeps this setpoint
until the start time of the next lower TSet. The room temperature control uses an
internal controller of which integral action time (P17) and room controller P-band
(P14) can be set.
optimum stop with room sensor
°C
room temperature
actual Tset
next lower Tset
early start room
off time control switchpoint
After reaching the target time, EOH3 still works with the supply temperature setpoint
from the heating curve. EOH3 sets the output Stop (YD2) to logical 0.
When preparing the Time Schedule, ensure that the switch point for cool-down is
always the latest possible time in the Time Schedule to avoid premature cool-down
and room temperatures outside the comfort zone.
Adaptation of Optimization
EOH3 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 behaviour of the heating
system and the building, EOH3 maintains a "model" of the building. The dead time
and time constants for the building determine the dynamic behaviour of the model.
EOH3 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 short (parameter P8) and Time constant short (parameter P9) define the
first model. This building model applies for a pre-heat that follows a short cool-down
(less than 24 hours).
Dead time long (parameter P10) and Time constant long (parameter P11) define the
second model. This building model applies for a pre-heat that follows a lengthy cool-
down (greater than 24 hours).
After a lengthy cool-down phase, the building walls are also cooled down and must
be heated if the room is to be heated.
When operating EOH3 without a room sensor, you must determine dead times and
time constants manually.
The following diagram shows how you can determine dead time (Tu) and time
constant (Tg) from the building characteristic curve.
177
ALPHABETIC REFERENCE
P7
room temperature
day setpoint
– next switch point
next
EN2B-0184 GE51 R0518 (Europe)
time
74-5577–33 (US)