Table 4 - Vav Modes Of Operation - York J Series Manual

Unit Sequence of Operation
TABLE 4 – VAV MODES OF OPERATION
Control
Occupied
'stat uses its programmed
Thermostat
occupied htg. Setpoint,
controls SAT to "no heat-
ing" (W1=OFF), or "full
heating (W1=ON). During
heating, supply fan at
100%. All VAV boxes fully
open-box heat relays en-
ergized from Heat1 output.
If hydronic heat, SAT con-
trolled to 2 stage hydronic
nd
heat setpoint.
Similar to thermostat
Network operation above, 'stat W1
Commu- signal is replaced by a
network command.
nicated
Sensor
Space Control algorithm is same
Sensor as for Morning WarmUp
cycle. RAT is controlled
to a programmed setpoint
w/ 2°F deadband when
space temperature drops
2°F below "VAV setpoint
for SAT reset". During heat-
ing, supply fan at 100%. All
VAV boxes fully open-box
heat relays energized from
Heat1 output. If hydronic
heat, SAT controlled to
2 stage hydronic heat
nd
setpoint.
None
(standalone) Occupied heating is never
used.
28
Heating
Unoccupied
Same as occupied heat-
ing, except 'stat uses its
programmed unoccupied
heating setpoint, 'stat gen-
erates "unoccupied" output
that overrides ODA damper
min. position to 0%. Dur-
ing heating, supply fan at
100%.
Similar to thermostat
operation above, 'stat W1
signal is replaced by a net-
work command. Network
supplies an "unoccupied"
command.
An external "unoccupied"
signal initiates this mode.
Space temperature is
controlled to a programmed
unoccupied htg. Setpoint
by cycling unit On/Off. Full
heating (all stages) is ON
when space temperature
drops 0.3°F below the
setpoint, OFF when tem-
perature is 0.1°F or less
below the setpoint for at
least 60 sec.
During heating, supply fan
at 100%. All VAV boxes
fully open-box heat relays
energized from Heat1
output. If hydronic heat,
SAT controlled to 2 stage
nd
hydronic heat setpoint.
An external "unoccupied"
signal initiates this mode,
unit shuts down.
Cooling
Occupied
'stat uses its programmed oc-
cupied clg. setpoint, 'stat Y1, Y2
outputs control SAT to "no cooling"
(Y1=OFF), "cooling to High SAT
setpoint" (Y1=ON) and "cooling
to Low SAT setpoint" (Y1=ON,
Y2=ON). ODA damper at min.
position (damper may modulate
open if free cooling is being used)
Supply fan controlled during cool-
ing by supply duct static, supply
fan uses a "soft start".
Similar to thermostat operation
above, 'stat signals are replaced
by network commands requesting
cooling to High SAT setpoint
(Stage 1), or to Low SAT setpoint
(Stage 2).
Cooling SAT setpoint is reset
by space temperature vs. "VAV
setpoint for SAT reset". Low SAT
setpoint used if space temperature
2°F above the reset setpoint, High
SAT setpoint if space temperature
0.5°F below the reset setpoint.
ODA damper at min. position
(damper may modulate open if
free cooling is being used) Supply
fan controlled during cooling by
supply duct static, supply fan uses
a "soft start".
SAT is controlled to a "Low SAT
setpoint". Supply fan always run-
ning, controlled by supply duct
static.
FORM 100.50-NOM7 (808)
Unoccupied
Same as occupied cooling,
except 'stat uses its pro-
grammed unoccupied cool-
ing setpoint, 'stat generates
"unoccupied" output that
overrides ODA damper min.
position to 0% (damper may
modulate open if free cool-
ing is being used). Supply
fan controlled during cooling
by supply duct static.
Similar to thermostat opera-
tion above, 'stat signals are
replaced by network com-
mands requesting cooling
to High SAT setpoint (Stage
1), or to Low SAT setpoint
(Stage 2), network supplies
an "unoccupied" command.
An external "unoccupied"
signal initiates this mode,
overrides ODA damper min.
position to 0% (damper may
modulate open if free cool-
ing is being used). Space
temperature is controlled to
programmed unoccupied
clg. Setpoint by cycling unit
On/Off. When space temper-
ature increases 0.3°F above
the setpoint, cooling runs
at programmed High SAT
setpoint, when temperature
is 0.1°F or less above the
setpoint for at least 60 sec,
unit turns OFF. During cool-
ing, supply fan is controlled
by supply duct static, supply
fan uses a "soft start".
An external "unoccupied"
signal initiates this mode,
unit shuts down.
JOHNSON CONTROLS