Honeywell EXCEL 5000 User Manual page 157

EXCEL CARE CONTROL ICONS ALPHABETIC REFERENCE
You can influence the type of optimization procedure that EOH uses by adjusting
Parameter P4, minimum preheat time. For very small values of P4, for example,
zero minutes, EOH only uses the variable time preheat (rapid preheating) because it
is never possible to reach the setpoint in zero minutes regardless of maximum
supply temperature. Large values of P4, such as several hours, have the opposite
effect. Large values cause variable temperature preheat with moderate supply
temperatures. During the preheat phase, EOH sends a logical 1 to output YD2.
During this time, EOH overwrites supply temperature setpoint in the application
program with the flow temperature setpoint (Y1). See previous diagrams.
If room temperature (X1) reaches the setpoint of the Time Program (X3) before the
target time point, EOH switches over to room control automatically. You must use an
internal PID controller whose integral action time (P16) and room control multiplier
(P15) can be set. After reaching the target point, EOH still works a half an hour
longer as a room controller. EOH then writes a logical 0 to output YD2 to allow the
application program to take control. This extended control by EOH compensates for
the cool-down effect from the walls and furniture after a rapid preheating so that an
almost constant room temperature is guaranteed with the transfer to temperature-
dependent control after ending the preheat optimization.
If the parameter "room sensor" is set to 2 (continuous room control), then room
control takes place all the time.
159 74-5577–33 (US)
EN2B-0184 GE51 R0518 (Europe)