JOHNSON CONTROLS
71
SECTION 5 – SEQUENCE OF OPERATION
FORM 100.50-NOM12
ISSUE DATE: 04/02/2019
5
4. Supply Fan VFD Speed
• This method uses built in logic that resets the
active SAT setpoint based on the current sup-
ply fan VFD speed.
• There is no VDC signal or BAS command
required to perform this sequence.
• The IPU board monitors the current supply
fan speed and resets the active SAT setpoint
as needed.
• A current supply fan speed that is equal to
or below the fan speed for high SAT causes
the active cooling SAT setpoint to be the SAT
high setpoint.
• A current supply fan speed that is equal to/
above the fan speed for low SAT causes the
active cooling SAT setpoint to be the SAT
low setpoint.
• A current supply fan speed that is between
the fan speed for high SAT and the fan speed
for low SAT causes the active cooling SAT
setpoint to be between the high SAT and low
SAT setpoints. See
.
SAT Reset Method Setpoint
• All setpoints for SAT reset method listed in the
above sequences can be found under the SET-
POINTS-COOLING menu.
• The reset method setpoints for RAT, OAT, or sup-
ply fan VFD speed are only shown if that SAT
reset method is the one selected.
• The heating SAT setpoint can be found under the
SETPOINTS-HEATING menu.
• These setpoints are also available on a BAS.
(Default = 55.0 °F)
(Default = 65.0
°
F)
Return Air Temp
(RAT)
Active SAT
Setpoint
Increasing RAT
SAT LOW SETPOINT
SAT HIGH SETPOINT
RAT SETPOINT
FOR HIGH SAT
RAT SETPOINT
FOR LOW SAT
LD10307A
FIGURE 29 -
ACTIVE SAT SETPOINT VERSUS RAT
Outside Air Temp
(OAT)
Active SAT
Setpoint
Increasing OAT
(Default = 65.0
°
F)
SAT HIGH SETPOINT
(Default = 55.0 °F)
SAT LOW SETPOINT
OAT SETPOINT
FOR HIGH SAT
OAT SETPOINT
FOR LOW SAT
LD12588
FIGURE 30 -
ACTIVE SAT SETPOINT VERSUS OAT