EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER
27 74-2958—1
Dirty Filter Monitor
The air filter in the air handler can be monitored b
the W7750
and an alarm is issued when the filter media needs
replacement. The two methods of monitorin
the filter are:
1.
Connectin
a differential pressure switch to a di
ital
input on the W7750A or W7750B,C.
2.
Wirin
a 2 to 10V differential pressure sensor to a
volta
e input on the W7750B,C. If the analo
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
e: 0 to 5 inw
0 to 1.25 kPa
,
and the Dirt
Filter alarm is issued when the pressure
drop across the filter exceeds the setpoint.
Indoor Air Quality (IAQ) Override
The Excel 10 W7750 Controller provides IAQ ventilation
control usin
one of two different methods of detectin
poor
air
ualit
. The first is with an IAQ switch device connected to
a di
ital input on the W7750 Controller, where a contact
closure indicates poor air
ualit
, and initiates the IAQ
Override mode. The device can detect poor air
ualit
usin
an
desired measure such as CO
2
, VOC, CO, etc. The
second method, which is onl
available on the W7750B,C, is
throu
h an analo
input that connects to a CO
2
sensor
2 to
10V
. The measured value of CO
2
from this sensor
0 to 2000
PPM
is compared to the setpoint
IAQSetpt
. When the CO
2
level is hi
her than the setpoint
800 PPM
adjustable
, the
IAQ Override is initiated. The IAQSetpt h
steresis is 50 PPM,
IAQ Override is deactivated at a CO
2
level less than 50 PPM
below setpoint.
The effect of initiatin
the IAQ Override mode is that the
economizer dampers are allowed to open above the standard
minimum position settin
to allow more fresh air to enter the
buildin
. See Appendix B—Se
uences of Operation, for
further control details.
Smoke Control
The Excel 10 W7750 Controller supports smoke-related
control strate
ies that are initiated either via a network
command
DestEmer
Cmd
or from a local
ph
sicall
connected
smoke detector di
ital input. The details of the
W7750 smoke-related control operation are described in
Appendix B—Se
uences of Operation.
Freeze Stat
A freeze stat can be monitored b
the W7750 and issue a
freeze stat alarm indicatin
the CVAHU is in dan
er of
freezin
its coil. The details of the W7750 freeze stat related
control operation are described in Appendix B—Se
uences of
Operation.
Modes of Operation
The possible modes of operation for the W7750 Controller are
listed in Table 5.
Table 5. Modes Of Operation For The Excel 10 W7750 Controller .
Mode Description Events causing a controller to switch to this mode
Effective Occupancy (User Address: StatusOcc)
OCCUPIED
Controller is in Occupied mode An
of the followin
: Network input
DestSchedOcc
containin
a
time-of-da
schedule fla
from either the Excel 10 Zone Mana
er or an
L
ON
W
ORKS
Bus Controller; Time Clock DI, Occupanc
Sensor DI; or
from Network input
DestManMode
for manual override to OCC mode.
DestManMode has the hi
hest priorit
, followed b
the Time Clock DI,
and then DestSchedOcc.
STANDBY
Controller is in Standb
mode Either:
A
Network input
DestSchedOcc
containin
a time-of-da
schedule fla
from the Excel 10 Zone Mana
er or other L
ON
W
ORKS
Bus node is STANDBY, or
B
Network input
DestSchedOcc
is
OCCUPIED and the Occupanc
Sensor DI is UNOCCUPIED.
UNOCCUPIED
Controller is in Unoccupied mode Network input
DestSchedOcc
containin
a time-of-da
schedule fla
from the Excel 10 Zone Mana
er or L
ON
W
ORKS
Bus, or the network
input DestManOcc has a value of UNOCCUPIED.
BYPASS
OCCUPIED
Controller is in Occupied mode throu
h
a B
pass command
This mode is derived from the schedule occupanc
DestSchedOcc
havin
a state of UNOCCUPIED and a manual re
uest for occupanc
from one of three sources. Two of these are si
nals ori
inated external
to the unit, and received b
DestManOcc and DestB
pass. The third
source for an occupanc
re
uest is from an override button located on
a wall module. These three sources are arbitrated in a scheme
determined b
the confi
uration parameter
Network Wins or Last-in
Wins from OvrdPriorit
.
Override Modes (User Address: StatusOvrd)
OCCUPIED
Controller occupanc
mode was
overridden to Occupied mode
Network input
DestManOcc
containin
a time-of-da
schedule
override si
nal of OCCUPIED from the Excel 10 Zone Mana
er or
other L
ON
W
ORKS
Bus device.
STANDBY
Controller occupanc
mode was
overridden to Standb
mode
Network input
DestManOcc
containin
a time-of-da
schedule
override si
nal of STANDBY from the Excel 10 Zone Mana
er or other
L
ON
W
ORKS
Bus device.
