Honeywell W7750A User Manual
EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER
59
74-2958—1
DIRTY FILTER MONITOR
The air filter in the air handler can be monitored by the W7750
and an alarm issued when the filter media needs replacement.
The two methods of monitoring the filter are:
and an alarm issued when the filter media needs replacement.
The two methods of monitoring the filter are:
1.
A differential pressure switch whose contacts are con-
nected to a digital input on the W7750A or W7750B,C;
and
nected to a digital input on the W7750A or W7750B,C;
and
2.
A 2-to-10V differential pressure sensor wired to a
current input on the W7750B,C. If the analog input
sensor is used, its measured value 0 to 5 inw
(0 to 1.25 kPa) is compared to a user-selectable
setpoint (FltrPressStPt—valid range: 0 to 5 inw
(0 to 1.25 kPa)), and the Dirty Filter alarm is issued
when the pressure drop across the filter exceeds the
setpoint.
current input on the W7750B,C. If the analog input
sensor is used, its measured value 0 to 5 inw
(0 to 1.25 kPa) is compared to a user-selectable
setpoint (FltrPressStPt—valid range: 0 to 5 inw
(0 to 1.25 kPa)), and the Dirty Filter alarm is issued
when the pressure drop across the filter exceeds the
setpoint.
START-UP
START_UP_WAIT is the first mode after application restart or
power-up. During START_UP_WAIT, the analog and digital
inputs are being read for the first time, no control algorithms
are active, and the physical outputs (fan and heat/cooling
stages) are in the de-energized position. The node remains in
power-up. During START_UP_WAIT, the analog and digital
inputs are being read for the first time, no control algorithms
are active, and the physical outputs (fan and heat/cooling
stages) are in the de-energized position. The node remains in
the START_UP_WAIT mode for a pseudo-random period
(depending on neuron_id) between 12 and 22 seconds and
then transitions to one of the operating modes, depending on
the inputs that are read from the physical and network inputs.
The pseudo random period prevents multiple controllers from
simultaneously starting major electrical loads when power is
restored to a building.
(depending on neuron_id) between 12 and 22 seconds and
then transitions to one of the operating modes, depending on
the inputs that are read from the physical and network inputs.
The pseudo random period prevents multiple controllers from
simultaneously starting major electrical loads when power is
restored to a building.
NOTES: After a controller download via Care/E-Vision, the
delayed reset time is bypassed and the controller
starts after a 40-second initialization.
starts after a 40-second initialization.
Not all network inputs can be received during the
START_UP_WAIT period because many network
variables are updated at a slower rate; therefore
some control decisions can be considered tempo-
rarily inappropriate.
START_UP_WAIT period because many network
variables are updated at a slower rate; therefore
some control decisions can be considered tempo-
rarily inappropriate.
Temperature Control Operations
See Fig. 49 for a diagram of a typical W7750 Unit.
Fig. 49. Schematic diagram for a typical W7750B Unit.
WINDOW CONTACT
OCCUPANCY
SENSOR
SENSOR
M
OA TEMP
FILTER
FAN
COOL
COIL
COIL
HEAT
COIL
COIL
DA TEMP
RA TEMP
EXCEL 10
W7750
CVAHU
W7750
CVAHU
T7770 OR T7560A,B
RETURN
AIR
AIR
DISCHARGE
AIR
AIR
OUTDOOR
AIR
AIR
CEILING
ROOF
-
+
M17488