JOHNSON CONTROLS
100
FORM 145.05-NOM7
ISSUE DATE: 10/31/2019
SECTION 5 – SEQUENCE OF OPERATION
shipped loose in the control enclosure and must be field
installed and wired to the Unit Controller. The sensor
is supplied with 25-foot leads terminated to plug onto
the Unit Controller. If a longer length is required, in-
line butt splices can be used to increase the length. It is
important the return air sensor be located so it senses
the true Return Air Temperature (RAT). The sensor is
connected at the J9 terminal strip, terminals 3 and 4.
Occupied Standby
The Unit Controller determines there is no demand
for cooling or heating based on the Current Zone
Temperature, through either a WIRED ZONE TEMP
(Hardwired) or COMM ZONE TEMP (Communi
-
cated) connection to the unit. The cooling or heating
operation starts to stage on or off depending on the set-
points shown in
.
Unoccupied Standby
The Unit Controller determines there is no demand
for cooling or heating based on the Current Zone
Temperature, through either a WIRED ZONE TEMP
(Hardwired) or COMM ZONE TEMP (Communi
-
cated) connection to the unit. The cooling or heating
operation starts to stage on or off depending on the set-
points shown in
.
Constant Volume Mode
A Constant Volume unit is controlled by one of two
“CONTROL METHODS.”
•
WIRED ZONE TEMP (Hardwired)
•
COMM ZONE TEMP (Communicated)
The “CONTROL METHOD” is entered into the Unit
Controller through the PROGRAM key, UNIT DATA
subsection of the User Interface.
Supply Fan Operation In Constant Volume
Operation
The Supply Fan is turned ON if the Supply Fan is OFF
for at least 60 seconds and one of the following condi-
tions apply:
• The UNIT MODE is OCCUPIED
• Or the unit is in the MORNING WARMUP mode
The Supply Fan is turned OFF if all of the following
conditions are met.
• The Supply Fan is ON for at least 60 seconds,
and the unit is in the UNOCCUPIED STANDBY
mode.
• 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 Sup-
ply Fan by checking the status of a digital input from
an air proving switch. After 120 seconds of operation,
the Unit Controller looks for a high state (24 volt input)
from the air proving switch circuit at terminal block
J13 pin 2 of the Unit Controller. It examines the current
state for 10 seconds. If the input does not go to a high
state during this time frame, the Unit Controller sets a
SUPPLY FAN LOCKOUT and shut down all unit sys-
tem operation.
Zone Temperature Control
(Hardwired or Communicated)
The unit compares the analog WIRED ZONE TEMP
or COMM ZONE TEMP input to the “OCC ZONE
COOLING,” “OCC ZONE HEATING,” “UNOCC
ZONE COOLING,” or “UNOCC ZONE HEATING”
setpoints to determine the sub-mode of operation. The
following parameters must be programmed through the
User Interface:
• SETPOINTS key, COOLING subsection:
• “OCC ZONE COOLING SETPOINT”
• “UNOCC ZONE COOLING SETPOINT”
• SETPOINTS key, HEATING subsection:
• “OCC ZONE HEATING SETPOINT”
• “UNOCC ZONE HEATING SETPOINT”
shows what the UNIT MODE
would be based on the difference between the zone
temperature and the zone temperature setpoints.
The only difference between Hardwired and Commun-
nicated is the method the Unit Controller uses to deter-
mine the ZONE TEMP. In the HARDWIRED mode,
the input is an analog input to the control. In the COM-
MUNICATED mode, the input is a serial input from a
Building Automated control system.