128
JOHNSON CONTROLS
5276178-JIM-C-0118
Sequence of Operation
Figure 60 shows what the UNIT MODE would be, based
on the difference between the zone temperature and the
zone temperature set points.
The only difference between Hard Wired and
Communicated is the method the Unit Controller uses
to determine the
“ZONE TEMP”
. In the Hard Wired
mode the input is an analog input to the control. In the
Communicated mode the input is a serial input from a
BAS control system.
Variable Air Volume Mode
Occupied Cooling
In the OCCUPIED COOLING mode the Unit Controller
monitors the “
RETURN AIR TEMP”
and compares
it to the
“RAT COOLING SETPOINT”
. The
“RAT
COOLING SETPOINT”
is entered into the Unit
Controller through the SET POINT key, COOLING
subsection of the User Interface. If the
“RETURN AIR
TEMP”
is equal to or greater than the
“RAT COOLING
SETPOINT”
plus 0.5°F the Unit Controller will place
the unit in the OCCUPIED COOLING mode.
The unit will remain in the OCCUPIED COOLING
mode until the
“RETURN AIR TEMP”
is equal to or less
than the “
RAT COOLING SETPOINT”
minus 0.5°F.
Occupied Heating
In the OCCUPIED HEATING mode the Unit Controller
monitors the
“RETURN AIR TEMP”
and compares it to
the
“RAT HEATING SETPOINT”
. The
“RAT HEATING
SETPOINT”
is entered into the Unit Controller through
the SET POINTS key, HEATING subsection of the User
Interface. If the
“RETURN AIR TEMP”
is equal to or
LESS than the
“RAT HEATING SETPOINT”
minus
0.5°F the Unit Controller will place the unit in the
OCCUPIED HEATING mode.
The unit will remain in the OCCUPIED HEATING
mode until the
“RETURN AIR TEMP”
is equal to or
greater than the
“RAT HEATING SETPOINT”
plus
0.5°F.
Unoccupied Cooling
In the UNOCCUPIED COOLING mode the Unit
Controller will monitor the
“ZONE TEMP”
and compare
it to the
“UNOCC ZONE COOLING SETPOINT”
. The
“UNOCC ZONE COOLING SETPOINT”
is set through
the SET POINTS key, COOLING subsection of the User
Interface. If the
“ZONE TEMP”
is equal to or greater
than the
“UNOCC ZONE COOLING SETPOINT”
temperature plus 0.5°F. the Unit Controller will place
the unit in the UNOCCUPIED COOLING mode.
The unit will remain in the UNOCCUPIED COOLING
mode until the
“ZONE TEMP”
is equal to or less than
the “
UNOCC ZONE COOLING SETPOINT”
minus
0.5°F.
Unoccupied Heating
In order for the UNOCCUPIED HEATING to function,
the “
NIGHT SET BACK”
setting must be set to
ENABLE. This can be done through the PROGRAM
key, HEATING subsection of the User Interface.
In the UNOCCUPIED HEATING mode the Unit
Controller will monitor the
“ZONE TEMP”
and compare
it to the
“UNOCC ZONE HEATING SETPOINT”.
The
“UNOCC ZONE HEATING SETPOINT”
is set through
the SET POINTS key, HEATING subsection of the User
Interface. If
“ZONE TEMP”
is equal to or less than
the
“UNOCC ZONE HEATING SETPOINT”
minus
0.5°F, the Unit Controller will place the unit in the
UNOCCUPIED HEATING mode.
The unit will remain in the UNOCCUPIED HEATING
mode until the
“ZONE TEMP”
is equal to or greater
than the “
UNOCC ZONE HEATING SETPOINT”
plus
0.5°F.
Summary of Contents for 40 25 TON
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