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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 b
y
the W7750
and an alarm issued when the filter media needs replacement.
The two methods of monitorin
g
the filter are:
1.
A differential pressure switch whose contacts are con-
nected to a di
g
ital 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 analo
g
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 ran
g
e: 0 to 5 inw
(
0 to 1.25 kPa
))
, and the Dirt
y
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
.
Durin
g
START_UP_WAIT, the analo
g
and di
g
ital
inputs are bein
g
read for the first time, no control al
g
orithms
are active, and the ph
y
sical outputs
(
fan and heat/coolin
g
sta
g
es
)
are in the de-ener
g
ized position. The node remains in
the START_UP_WAIT mode for a pseudo-random period
(
dependin
g
on neuron_id
)
between 12 and 22 seconds and
then transitions to one of the operatin
g
modes, dependin
g
on
the inputs that are read from the ph
y
sical and network inputs
.
The pseudo random period prevents multiple controllers from
simultaneousl
y
startin
g
ma
j
or electrical loads when power is
restored to a buildin
g
.
NOTES: After a controller download via Care/E-Vision, the
dela
y
ed reset time is b
y
passed and the controller
starts after a 40-second initialization.
Not all network inputs can be received durin
g
the
START_UP_WAIT period because man
y
network
variables are updated at a slower rate; therefore
some control decisions can be considered tempo-
raril
y
inappropriate.
Temperature Control Operations
See Fi
g
. 49 for a dia
g
ram of a t
y
pical W7750 Unit.
Fig. 49. Schematic diagram for a typical W7750B Unit.
WINDOW CONTACT
OCCUPANCY
SENSOR
M
OA TEMP
FILTER
FAN
COOL
COIL
HEAT
COIL
DA TEMP
RA TEMP
EXCEL 10
W7750
CVAHU
T7770 OR T7560A,B
RETURN
AIR
DISCHARGE
AIR
OUTDOOR
AIR
CEILING
ROOF
-
+
M17488