JOHNSON CONTROLS
109
SECTION 5 – SEQUENCE OF OPERATION
FORM 145.05-NOM7
ISSUE DATE: 10/31/2019
5
The unit remains 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
To operate in the UNOCCUPIED COOLING mode,
“NIGHT SET BACK” must be set to USER ENABLE
using the PROGRAM key, HEATING subsection of
the User Interface. In the UNOCCUPIED COOL-
ING mode, the Unit Controller monitors the ZONE
TEMP and compare it to the “UNOCC ZONE COOL-
ING SETPOINT.” The “UNOCC ZONE COOLING
SETPOINT” is set through the SETPOINTS key,
COOLING subsection. If the ZONE TEMP is equal
to or greater than the “UNOCC ZONE COOLING
SETPOINT” temperature plus 0.5°F. the Unit Control-
ler places the unit in the UNOCCUPIED COOLING
mode.
The unit remains 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
To operate in the UNOCCUPIED HEATING mode,
“NIGHT SET BACK” must be set to USER ENABLE
using the PROGRAM key, HEATING subsection. In
the UNOCCUPIED HEATING mode, the Unit Con-
troller monitors the ZONE TEMP and compare it to
the “UNOCC ZONE HEATING SETPOINT” of the
User Interface. The “UNOCC ZONE HEATING
SETPOINT” is set through the SETPOINTS 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 Con-
troller places the unit in the UNOCCUPIED HEAT-
ING mode.
The unit remains in the UNOCCUPIED HEATING
mode until the ZONE TEMP is equal to or greater than
the “UNOCC ZONE HEATING SETPOINT” plus
0.5°F.
A zone temperature signal must be pres-
ent for the unit to function. If the unit is
set for "NIGHT SET BACK" and goes
unoccupied without a zone temperature
signal, it shuts down.
Variable Air Volume
The “SUPPLY AIR TEMP ACTIVE SP” is always de-
rived from three programmed parameters: “SAT HIGH
SETPOINT,” “SAT LOW SETPOINT,” and the “SAT
RESET METHOD.” The Unit Controller determines
the “SUPPLY AIR TEMP ACTIVE SP” value to use
based on the reset command sent to the controller.
There are four options available to select from for the
reset command method. “SAT RESET METHOD” can
be set for NONE, OUTSIDE AIR, RETURN AIR, or
SUPPLY FAN SPEED. If NONE is used and no input
is available, the Unit Controller controls to the “SAT
HIGH SETPOINT.” The following parameters are pro-
grammed through the User Interface:
• PROGRAM key, COOLING subsection: “SAT
RESET METHOD”
• SETPOINTS key, COOLING subsection:
• “SAT LOW SETPOINT”
• “SAT HIGH SETPOINT”
• “OAT SETPOINT FOR LOW SAT”
• “OAT SETPOINT FOR HIGH SAT”
• “RAT SETPOINT FOR LOW SAT”
• “RAT SETPOINT FOR HIGH SAT”
• “FAN SPEED SETP FOR LOW SAT”
• “FAN SPEED SETP FOR HIGH SAT”
(SAT = Supply Air Temperature)
(SP = Setpoint)
Communicated SAT Reset
When the “SAT RESET METHOD” is set to “NONE,”
the Unit Controller monitors the communicated input,
SAT_RST_BAS, AV28, to determine the value of the
“SUPPLY AIR TEMP ACTIVE SP.” If SAT_RST_BAS
is set to 0.0, the “SUPPLY AIR TEMP ACTIVE SP”
is the “SAT HIGH SETPOINT.” If SAT_RST_BAS
is set to 5.0, the “SUPPLY AIR TEMP ACTIVE SP”
is “SAT LOW SETPOINT.” When SAT_RST_BAS is
between 0.0 and 5.0, the “SUPPLY AIR TEMP AC-
TIVE SP” is linearly interpolated between the “SAT
HIGH SETPOINT” and the “SAT LOW SETPOINT”
(see
).
