Honeywell EXCEL 5000 User Manual page 240

ALPHABETIC REFERENCE
74-5577–33 (US)
EN2B-0184 GE51 R0518 (Europe)
When the ZEB/Load reset mode (P8) in the internal parameters dialog box is equal
to 1 (ZEB), 3 (Cooling control), or 4 (Heating and cooling), the ZEB energy
management function calculates a cooling setpoint as follows.
If the warmest temperature sensor value goes above the ZEB upper limit,
mechanical cooling is enabled. Cooling is then controlled to maintain the cooling
setpoint, Y4. To calculate the cooling setpoint, the maximum zone temperature (the
highest value of all the configured zone sensors), Input X1, is required. Then the
cooling setpoint is calculated based on a linear relationship with X1 and is sent to
output Y4.
If the highest zone temperature is at or above the upper limit of the cooling band,
then the minimum (lowest) cooling setpoint, P5, is used. This upper cooling band
limit is specified by adding 3 times the comfort range, P3 (typically set to 4FDeg), to
the room temperature setpoint (Input X5):
Y4=P5, if X1 > X5 + (3*P3)
If the highest zone temperature is at or below the lower limit of the cooling band, an
offset called the "cooling reset range" (P12) is added to the minimum cooling
setpoint, P5, and this sum is used for the cooling setpoint, Y4. The lower cooling
band limit is specified by adding the comfort range, P3, to the room temperature
setpoint, X5:
Y4 = P5 + P12, if X1 < X5 + P3
When the highest zone temperature is inside the cooling band, the cooling setpoint,
Y4, is calculated with the following formula:
If the highest zone temperature sensor value is in the cooling band area (or higher),
mechanical cooling is enabled, that is, YD2 is set to 1.
Example:
Maximum zone temperature X1 = 75
Minimum zone temperature X2 = 66
Average zone temperature X3 = 68
Room temperature setpoint X5 = 68
Comfort range P3 = 4FDeg
Min. cooling setpoint P5 = 55
Cooling reset range P12 = 10FDeg
ZEB Heating Operation
When the ZEB/Load reset mode in the internal parameters dialog box is equal to 1
(ZEB), 2 (Heating control), or 4 (Heating and cooling), the application also includes
heating setpoint management as follows.
If the zone temperature falls below the zero energy range, ZEB implements a linear
release of the heating energy through a continuous increase of the heating setpoint
(Y3). The minimum zone temperature (X2) is the determining factor for the release
of heating and the calculation of the heating setpoint (Y3).
Y3=P6, if X2 < X5 - (3*P3)
This relationship means that the maximum heating setpoint (P6) is demanded when
the lowest zone temperature is at or below the lower end of the heating range.
Y3 = P6 -P11, if X2 = X5 - P3
This relationship means that the maximum heating setpoint (P6) minus the heating
reset range (P11) is demanded when the lowest zone temperature just falls below
the zero energy range.
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EXCEL CARE CONTROL ICONS