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EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER
57 74-2958—1
DestB
y
pass - Has possible states: B
y
pass On,
B
y
pass Off or Not Assi
g
ned
(
not active
)
.
This input places the controller in an
untimed
b
y
pass state or turns off the
b
y
pass mode. This source is second in
priorit
y
to DestManOcc under the same
arbitration schemes mentioned above.
Override Button -The wall module Override pushbutton
can command status of B
y
pass,
Continuous Unoccupied and Not
Assi
g
ned. This source has the lowest
priorit
y
status in the above mentioned
schemes. The above mention sources
of override must be either Not Assi
g
ned
or Off before the Override pushbutton
affects the manual override status in the
Network Wins scheme. All actions, in
this case, taken from the Override
pushbutton are locked out.
B
y
pass status is a controller-timed
event whose duration is set in B
y
pTime.
Upon expiration of the timer, the status
returns to Not Assi
g
ned. The status of
this input can be overridden with the
receipt of Not Assi
g
ned from
DestManOcc. This, in effect, cancels a
timed b
y
pass or a continuous
unoccupied mode.
The Override pushbutton can be
confi
g
ured as Normal
(
all of the above
mentioned states are possible
)
, B
y
pass
Onl
y
(
B
y
pass and Not Assi
g
ned onl
y)
or
None
(
effectivel
y
Disablin
g
the Override
pushbutton
)
.
TIME CLOCK (Occ_Time_Clock)
OccTimeClock is the state of the di
g
ital input confi
g
ured and
wired to a time clock. When the di
g
ital input is detected to be
Closed
(
Occupied
)
, the scheduled occupanc
y
will be
OC_OCCUPIED. If the detected state of the di
g
ital input is
Open
(
Unoccupied
)
, then the scheduled occupanc
y
will be
OC_UNOCCUPIED. If the Occ_Time_Clock is not confi
g
ured,
then either the DestSchedOcc network input received from a
central control or the time clock that is broadcast from a
Sched_Master confi
g
ured W7750, controls the occupied
mode.
SCHEDULE MASTER (Sched_Master)
Sched_Master is the state of a di
g
ital input that is confi
g
ured
and wired to the W7750. If the Sched_Master input is closed
(
input shorted
)
, the node is the schedule master and the state
of the locall
y
connected time clock will be broadcast out over
the L
ON
W
ORKS
Bus to the other W7750 controllers. If the
Sched_Master input is open, then the node is not a schedule
master and the local time clock will not be sent out over the
L
ON
W
ORKS
Bus even if the time clock input is confi
g
ured.
However, the DestSchedOcc network input received from a
central control has a hi
g
her priorit
y
than the local time clock,
and therefore overrides the local time clock. The W7750
controllers automaticall
y
bind without the need for a
confi
g
uration tool.
SETPOINT RAMPING
The W7750 Controller incorporates a rampin
g
feature that
g
raduall
y
chan
g
es the space setpoints between occupanc
y
modes. This feature is onl
y
operational if the network variable
inputs DestSchedOcc, TodEventNext, and Time Until Next
Chan
g
e Of State
(
TUNCOS
)
are bein
g
used to chan
g
e the
W7750 Occupanc
y
mode. The applicable Setpoints are
OaTempMinHtRamp, OaTempMaxHtRamp, MinHtRamp and
MaxHtRamp
(
for HEAT mode operation
)
, and
OaTempMinClRamp, OaTempMaxClRamp, MinClRamp and
MaxClRamp
(
for the COOL mode operation
)
. See Fi
g
. 46 for a
pictorial representation of how these setpoints interact.
Durin
g
recover
y
operation, the setpoint chan
g
es at a rate in
de
g
rees per hour dependin
g
on the outdoor air temperature. If
there is no outdoor air temperature sensor available, then
MinHtRamp is used as the recover
y
rate.
Fig. 46. Setpoint ramping parameters with ramp rate
calculation.
NOTE: Recover
y
rampin
g
applies between scheduled
heatin
g
or coolin
g
setpoint chan
g
es from
UNOCCUPIED to STANDBY, UNOCCUPIED to
OCCUPIED, and STANDBY to OCCUPIED.
Scheduled setpoint chan
g
es from OCCUPIED to
UNOCCUPIED or OCCUPIED to STANDBY do not
use a ramped setpoint but instead use a step chan
g
e
in setpoint. Recover
y
ramps be
g
in before the next
scheduled occupanc
y
time and are ramped from the
setpoint for the existin
g
scheduled occupanc
y
state
to the setpoint for the next occupanc
y
state.
RECOVERY RAMPING FOR HEAT PUMP SYSTEMS
When the node is controllin
g
heat pump e
q
uipment, durin
g
the
recover
y
ramps, the heatin
g
setpoint is split into a heat pump
setpoint
(
for compressors
)
and an auxiliar
y
heat setpoint
(
for
auxiliar
y
heat sta
g
es
)
. The heat pump setpoint is a step
chan
g
e at the recover
y
time prior to the OCCUPIED time.
Recover
y
time is computed from the confi
g
ured heat recover
y
ramp rate. The recover
y
time is calculated:
Recover
y
time =
(
OCC setpoint - current setpoint
)
/ramp rate
See Fi
g
. 47 for the various setpoints.
HEAT RECOVERY
RAMP RATE
(DEGREES/HOUR)
MaxHtRam
MinHtRam
OaTempMinHtRa OaTempMaxHtRam
OUTDOOR AIR
TEMPERATURE
M10109