135
JOHNSON CONTROLS
5276178-JIM-C-0118
5
SUPPLY FAN OPERATION
Constant Volume Operation
The Supply Fan will be turned ON if the following
conditions are met:
•
The Supply Fan has been OFF for at least 60 sec-
onds and one of the following conditions apply.
The FAN (G) digital input is high, 24V is present
at terminal “G” of the unit low voltage terminal
block.
Or the
“UNIT MODE”
is
other than
OCCUPIED
STANDBY OR UNOCCUPIED STANDBY.
Or the unit is in the MORNING WARMUP
mode.
Or the unit modes of operation are CONTINU-
OUS VENT and OCCUPIED.
“CONTINUOUS
VENT”
is ENABLED through the PROGRAM
key, VENTILATION subsection of the User
Interface. This energizes the Supply Fan on a
CONSTANT VOLUME unit any time the operat-
ing mode is Occupied.
The Supply Fan will be turned OFF if all of the following
conditions are met:
•
The Supply Fan has been ON for at least 60 sec-
onds.
•
The unit is in the OCCUPIED OR UNOCCUPIED
STANDBY mode.
•
The FAN (G) digital input is low, 24V is not pres-
ent at “G” of the low voltage terminal block.
•
The INACTIVE HEATING TIME is greater than
or equal to 60 seconds.
•
The INACTIVE COOLING TIME is greater than
or equal to 60 seconds.
•
The SUPPLY AIR TEMP is less than or equal to
85.0°F.
•
And either
“CONTINUOUS VENT”
is OFF or
the CURRENT OPER MODE is set to UNOC-
CUPIED.
The Unit Controller monitors the operation of the Supply
Fan by checking the status of a digital input from an
air proving switch. After 45 seconds of operation, the
Unit Controller looks for a high state (24V input) from
the air proving switch circuit at terminal block TB7 pin
10 of the Unit Controller. It then examines the current
state for 10 seconds. If the input does not go to a high
state during this time frame the Unit Controller will set
a SUPPLY FAN LOCKOUT and shut down all unit
system operation.
Variable Air Volume (VAV)
The Supply Fan will be turned ON if
the Supply Fan
has been OFF for at least 60 seconds and one of the
following conditions apply:
•
The FAN (G) digital input is high, 24V is present
at terminal “G” of the unit low voltage terminal
block.
•
Or the CURRENT OPER MODE is set to OC-
CUPIED.
•
Or the unit is in the MORNING WARMUP
mode.
•
Or the UNIT MODE is UNOCCUPIED HEAT-
ING OR UNOCCUPIED COOLING.
The Supply Fan will be turned OFF if all the following
conditions are met:
•
The Supply Fan has been ON for at least 60
seconds.
•
The unit is in the UNOCCUPIED STANDBY
mode.
•
The FAN (G) digital input is low, 24V is not
present at “G” of the unit low voltage terminal
block.
•
The INACTIVE HEATING TIME is greater than
or equal to 60 seconds.
•
The INACTIVE COOLING TIME is greater
than or equal to 60 seconds.
•
The SUPPLY AIR TEMP is less than or equal
to 85.0°F.
The Unit Controller monitors the operation of the
Supply Fan by checking the status of a digital input
from an air proven switch. After 45 seconds of
operation, the control looks for a high state (24V input)
from the air proving switch circuit at terminal block
TB7 pin 10 of the Unit Controller. It then examines
the current status for 10 seconds. If the input does
not go to a high state during this time frame the Unit
Controller will set a SUPPLY FAN LOCKOUT and
shut down all unit system operation.
The Unit Control uses a proportional-integral control
algorithm to maintain the
“DUCT STATIC PRESSURE”
by varying the speed of the supply fan. As the pressure
goes up, the speed goes down.
Summary of Contents for 40 25 TON
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