Honeywell EXCEL 10 W7752D - Manual (Page 6)

EXCEL 10 FCU CONTROLLER LNS PLUG-INS USER GUIDE
EN2B-0285GE51 R0909 4
Fig. 3. Control sequence diagram
Setpoints
Setpoint Knob
The Excel 10 FCU Controllers may be hardwired to an Excel
10 wall module equipped with a setpoint knob. When the
Excel 10 FCU Controller has been configured (using the LNS
plug-in tool) to read input from the wall module's setpoint
knob, the value from the setpoint knob is used to calculate the
"occupied" setpoint for the heating and the cooling modes.
There are two configurations which determine how the
setpoint used by the control algorithm is calculated: "relative"
(or "offset") and "absolute middle". When configured for
"relative", the Excel 10 wall module setpoint knob represents
a number from -9...+9 DDF(-5...+5 K) which is added to the
configured "occupied" and "standby" setpoints for the heating
and the cooling modes. When configured to "absolute
middle", the setpoint knob becomes the mid-point of the Zero
Energy Band (ZEB) extending between the "occupied" or
"standby" setpoints for the heating and the cooling modes.
The range of the ZEB is found by taking the difference
between the "occupied" or "standby" setpoints configured for
the heating and the cooling modes; in the case of "absolute
middle", the current "occupied" and "standby" setpoints are
therefore found as follows:
When the Excel 10 FCU Controller is in the "occupied" mode:
nvoActiveSetPt (in cooling mode) =
nvoSensor.remote_set_point + (Cooling Occupied
Setpoint - Heating Occupied Setpoint) / 2
nvoActiveSetPt (in heating mode) =
nvoSensor.remote_set_point - (Cooling Occupied
Setpoint - Heating Occupied Setpoint) / 2
for Standby:
nvoActiveSetPt (in cooling mode) =
nvoSensor.remote_set_point + (Cooling Standby
Setpoint - Heating Standby Setpoint) / 2
nvoActiveSetPt (in heating mode) =
nvoSensor.remote_set_point - (Cooling Standby
Setpoint - Heating Standby Setpoint) / 2
When the Excel 10 FCU Controller is in the "unoccupied"
mode, the remote setpoint knob is ignored, and the con-
figured setpoints for this mode are used instead.
Setpoint Limits
Setpoints are limited to the range of 50...95°F (10...35°C).
The value of the setpoint knob is limited to the range provided
by the configuration parameters Maximum Limit Setpoint pot
and Minimum Limit Setpoint pot. In the case of absolute
"occupied" and "standby" setpoints, the setpoint knob still
represents the mid-point of the ZEB, even when set to either
of these limits. The actual setpoints are given by the
equations shown above. When the setpoint knob is configured
to be "relative", the lowest actual "occupied" setpoint allowed
is equal to SptHeatOcc - SptKnobLowLim, and the highest
allowed is equal to SptCoolOcc + SptKnobHiLim. The lowest
and highest "standby" setpoints are found in an analogous
fashion.
Setpoint from Network
When the Excel 10 FCU Controller is not configured to be
hardwired to a wall module, nviSetPoint must be bound to
another node that provides a setpoint. When bound and when
a valid update is received, nviSetPoint is used with the
appropriate ZEB:
• ZEBoccupied = Cooling Occupied Septoint - Heating
Occupied Setpoint
• ZEBstandby = Cooling Standby Setpoint - Heating
Standby Setpoint
The "unoccupied" setpoint does not depend on nviSetPoint at
all.
Setpoint Offset
Third-party nodes may be bound to nviSetPtOffset to shift the
setpoint in the range of -18 to 18 DDF (-10 K to 10 K).