Honeywell EXCEL 5000 User Manual page 171

EXCEL CARE CONTROL ICONS ALPHABETIC REFERENCE
During this preheat phase, EOH3 transmits a 1 to the output Start (YD2). You can
use this output to determine to overwrite the supply temperature setpoint from the
normal application program by the flow temperature setpoint (Y1) from EOH3.
If the target time point of the switching program occurs in this time, EOH3 sets the
output Start (YD2) to logical zero, meaning that the requirements of the normal
applications program again apply. EOH3 calculates the supply temperature setpoint
(Y1) in accordance with the heating curve. Parameter P16 provides the curvature.
Parameter P17 provides the slope which is displaced in accordance with the room
temperature setpoint including the increase (see "HCA Icon" section for further
explanations of the heating curve).
Heating Optimization with Room Sensor
EOH3 can calculate the residual heat in a building and the exact preheat points only
if there is a room sensor TRm (X2).
In order not to boost always with the maximum flow temperature P16, we will boost
with the value defined in the heating curve using the next TSet – see equation
below:
T2boost = HC (next TSet + P22 * (next TSet - actual TSet), TOat, P16, P17)
Parameters P16 (curvature) and P17 (Slope) belong to the heating curve.
Parameter P15 limits the supply temperature setpoint (TSet) to the maximum
permissible flow temperature.
During the setback period, the outdoor temperature, the current room temperature,
and the T2boost are used to decide the start time of the preheating phase. First the
heating curve equation is used to calculate the asymptotic room temperature limit
T1lim (reverse heating curve).
T2boost = HC (T1lim, TOat, P16, P17)
During the preheating period, TSup is repeatedly updated by the heating curve to
allow variations of the outdoor temperature. The estimate of T1lim remains
unchanged from the value calculated at the beginning of the pre-heat.
If the room temperature setpoint is reached earlier than the target point in time,
room temperature control takes over.
After the target point in time is reached, room temperature control is enabled for
another 30 minutes. The room temperature control is meant to compensate for
cooling effects caused by walls and furniture after boost heating so that after switch
over to weather responsive control, the room temperature remains nearly constant.
Output Start (YD2) has a value of 1.0 between the start of the preheat time and
programmed time. For all other times, Start (YD2) = 0.
Variable Time Preheat
During the pre-heat period, the supply water temperature used will be T2boost (see
equation above) except if less than the minimum preheat time (P1) would then be
required. In this case the minimum time is used and the supply water temperature is
re-calculated accordingly.
These two complementary ways of preheating are called time-variable and
temperature-variable optimization respectively and the correct method will be
selected.
During the setback period, the outdoor temperature, the current room temperature,
and the T2boost are used to decide the start time of the preheating phase. First the
heating curve equation is used to calculate the asymptotic room temperature limit
T1lim (reverse heating curve).
T2boost = HC (T1lim, TOat, P16, P17)
Then the building model is used to predict what the room temperature would be at
the time of the next switchpoint if the heating would be switched on immediately.
When this predicted temperature is less than the next TSet (room temperature
setpoint), then it is time to begin the pre-heat period and switch on the heating.
173 74-5577–33 (US)
EN2B-0184 GE51 R0518 (Europe)