A SERVICE OF

logo

Open as PDF
next previous
EXCEL 10 W7750A,B,C CONSTANT VOLUME AHU CONTROLLER
55 74-2958—1
than Intermittent Fan
(
see Fan Operation in this Appendix
)
,
and the mode is Occupied when the RmTemp value becomes
invalid, the fan continues to run.
REMOTE SETPOINT (RmtStptPot)
This is the Setpoint Potentiometer contained in the T7770 or
the T7560A,B Wall Module. When confi
g
ured, this occupant
value is set to calculate the actual coolin
g
or heatin
g
Occupied Setpoint. There are two options for how to calculate
the actual setpoint to be used b
y
the temperature control
al
g
orithm:
(
Offset
)
and
(
Absolute Middle
)
. When SetPtKnob is
set to Offset, the Wall Module setpoint knob represents a
number from -9° to +9°F
(
-5° to +5°C
)
which is added to the
software occupied setpoints for the heat and the cool modes
(
CoolOccSpt and HeatOccSpt
)
. When SetPtKnob is set to
Absolute Middle, the setpoint knob becomes the center of the
Zero Ener
gy
Band
(
ZEB
)
between the coolin
g
and heatin
g
occupied setpoints. The size of the ZEB is found b
y
takin
g
the
difference between the software heatin
g
and coolin
g
occupied
setpoints; therefore, for Absolute Middle, the actual setpoints
are found as follows:
ActualCoolSpt
=
RmtStptPot +
(
CoolOccSpt - HeatOccSpt
)
/ 2
ActualHeatSpt
=
RmtStptPot -
(
CoolOccSpt - HeatOccSpt
)
/ 2
Durin
g
Standb
y
and Unoccupied times, the remote setpoint
pot is not referenced, and the software setpoints for those
modes are used instead.
SETPOINT LIMITS (LoSetptLim AND HiSetptLim)
Remote setpoint pot limits are provided b
y
LoSetptLim and
HiSetptLim. The occupied setpoints used in the control
al
g
orithms are limited b
y
these parameters. When the setpoint
knob is confi
g
ured to be of t
y
pe Absolute Middle, the lowest
actual setpoint allowed is e
q
ual to LoSetptLim, and the
hi
g
hest actual setpoint allowed is e
q
ual to HiSetptLim. When
the setpoint knob is confi
g
ured to be an Offset t
y
pe, the lowest
actual setpoint allowed is e
q
ual to HeatOccSpt - LoSetptLim,
and the hi
g
hest allowed is e
q
ual to CoolOccSpt + HiSetptLim.
BYPASS MODE (StatusOvrd AND StatusLed)
Durin
g
Unoccupied periods, the facilit
y
occupant can re
q
uest
that Occupied temperature control setpoints be observed b
y
depressin
g
the B
y
pass pushbutton on the wall module. When
activated, the controller remains in B
y
pass mode until:
1.
B
y
pass Duration Settin
g
has timed out
(
B
y
pTime
)
, or
2.
User a
g
ain presses the Wall Module pushbutton to
switch off B
y
pass mode, or
3.
Occupanc
y
schedule
(
DestSchedOcc network input or
TimeClckOcc di
g
ital input
)
switches the mode to
Occupied.
4.
User sets the DestManOcc network point to Not
Assi
g
ned.
The LED on the T7770 Wall Module
(
Override LED
)
indicates
the current b
y
pass mode status
(
see the T7770C,D Wall
Module B
y
pass Pushbutton and Override LED section
)
. The
LCD on the T7560 Di
g
ital Wall Module indicates the current
b
y
pass mode status
(
see the T7560A,B Di
g
ital Wall Module
B
y
pass Pushbutton and LCD Occupanc
y
S
y
mbols section
)
.
BypassTime
B
y
passTime is the time between the pressin
g
of the override
button at the wall module
(
or initiatin
g
OC_BYPASS via
nviManOcc
)
and the return to the ori
g
inal occupanc
y
state.
When the b
y
pass state has been activated, the b
y
pass timer
is set to B
y
passTime
(
default of 180 minutes
)
.
OverrideType
OverrideT
y
pe specifies the behavior of the override button on
the wall module. There are three possible states that have the
followin
g
meanin
g
s:
NONE disables the override button.
NORMAL causes the override button to set the OverRide
state to OC_BYPASS for B
y
passTime
(
default 180
minutes
)
, when the override button has been pressed
for approximatel
y
1 to 4 seconds, or to set the OverRide
state to UNOCC when the button has been pressed for
approximatel
y
4 to 7 seconds. When the button is
pressed lon
g
er than approximatel
y
7 seconds, then the
OverRide state is set to OC_NUL
(
no manual override is
active
)
.
BYPASS_ONLY causes the override button to set the
OverRide state to OC_BYPASS for B
y
passTime
(
default
180 minutes
)
, on the first press
(
1 to 7 seconds
)
. On the
next press, the OverRide state is set to OC_NUL
(
no
manual over ride is active
)
.
OverridePriority
OverridePriorit
y
confi
g
ures the override arbitration between
nviManOcc, nviB
y
pass.state, and the wall module override
button. There are two possible states which have the followin
g
meanin
g
s:
LAST specifies that the last command received from either
the wall module or nviManOcc determines the effective
override state.
NET specifies that when nviManOcc is not OC_NUL, then
the effective occupanc
y
is nviManOcc re
g
ardless of the
wall module override state.
CYCLES PER HOUR (ubHeatCph AND ubCoolCph)
ubHeatCph specifies the mid-load number of on / off c
y
cles
per hour
(
default is 6
)
, when the mode is HEAT. ubCoolCph
specifies the mid-load number of on / off c
y
cles per hour
(
default is 3
)
, when the mode is COOL. This is to protect the
mechanical e
q
uipment a
g
ainst short c
y
clin
g
causin
g
excessive wear. In addition the c
y
cle rate specifies the
minimum on and off time accordin
g
to Table 17.
T7770C,D OR T7560A,B WALL MODULE BYPASS PUSHBUTTON
OPERATION
The Wall Module B
y
pass pushbutton is located on both the
T7770C,D or the T7560A,B Wall Modules, see Fi
g
. 43 and 44.
The b
y
pass pushbutton can chan
g
e the controller into various
occupanc
y
modes, see Table 16.
Table 16. Bypass Pushbutton Operation.
NOTES: If the pushbutton is held down for lon
g
er than seven
seconds, the controller reverts back to No Override
and repeats the c
y
cle above. See Fi
g
. 45.
Continuous Occupied override mode can onl
y
be
initiated remotel
y
; that is, over the L
ON
W
ORKS
Bus
network.
If the pushbutton is
held down for
But for not
more than The resulting mode is
Less than 1 second — No Override is active
1 second 4 seconds B
y
pass
(
a timed Occupied
Override
)
4 seconds 7 seconds Continuous Unoccupied
Override