Johnson Controls LSWU025, Manual

Page: 110 / 210

JOHNSON CONTROLS
110
FORM 145.05-NOM7
ISSUE DATE: 10/31/2019
SECTION 5 – SEQUENCE OF OPERATION
SAT HIGH SETPOINT
(Default = 65.0 °F)
Active SAT
Setpoint
SAT LOW SETPOINT
(Default = 55.0 °F)
Supply Air Temp Rst
0.0 5.0
FIGURE 65 - ACTIVE SAT SETPOINT VS. SUPPLY
AIR TEMP RST VOLTAGE
LD13961
Outside Air Based SAT Reset
When the “SAT RESET METHOD” is set to OUTSIDE
AIR, the Unit Controller monitors the OUTSIDE AIR
TEMP and sets the “SUPPLY AIR TEMP ACTIVE SP”
to a value between the “SAT HIGH SETPOINT” and the
“SAT LOW SETPOINT.” If the OUTSIDE AIR TEMP
is equal to or less than the “OAT SETPOINT FOR
HIGH SAT,” the “SUPPLY AIR TEMP ACTIVE SP”
is the “SAT HIGH SETPOINT.” If the OUTSIDE AIR
TEMP is equal to or greater than the “OAT SETPOINT
FOR LOW SAT,” the “ACTIVE SAT SP” is the “SAT
LOW SETPOINT.” When the OUTSIDE AIR TEMP
is between the “OAT SETPOINT FOR HIGH SAT”
and the “OAT SETPOINT FOR LOW SAT,” the “SUP-
PLY AIR TEMP ACTIVE SP” is linearly interpolated
between the “SAT HIGH SETPOINT” and the “SAT
LOW SETPOINT” (see Figure 55 on page 110 ).
SAT HIGH SETPOINT
(Default = 65.0 °F)
SAT LOW SETPOINT
(Default = 55.0 °F)
Outside Air Temp
(OAT)
OAT SETPOINT
FOR HIGH SAT
OAT SETPOINT
FOR LOW SAT
Active SAT
Setpoint
Increasing OAT
FIGURE 66 - ACTIVE SAT SETPOINT VS. OUTSIDE
AIR TEMP
LD12588
Supply Fan Speed Based SAT Reset
When the “SAT RESET METHOD” is set to “SUP-
PLY FAN SPEED,” the Unit Controller monitors the
“
SUPPLY FAN VFD SPEED” command and set the
“SUPPLY AIR TEMP ACTIVE SP” to a value between
the “SAT HIGH SETPOINT” and the “SAT LOW
SETPOINT.” If the “SUPPLY FAN VFD SPEED” is
equal to or greater than the “FAN SPEED SETP FOR
LOW SAT,” the “SUPPLY AIR TEMP ACTIVE SP”
is the “SAT LOW SETPOINT.” If the “SUPPLY FAN
VFD SPEED” is equal to or less than the “FAN SPEED
SETP FOR HIGH SAT,” the
“
SUPPLY AIR TEMP
ACTIVE SP” is the “SAT HIGH SETPOINT.” When
the “SUPPLY FAN VFD SPEED” is between the
“FAN SPEED SETP FOR LOW SAT” and the “FAN
SPEED SETP FOR HIGH SAT,” the “SUPPLY AIR
TEMP ACTIVE SP” is linearly interpolated between
the “SAT HIGH SETPOINT” and the “SAT LOW
SETPOINT” (see Figure 56 on page 110 ).
FIGURE 67 - ACTIVE SAT SETPOINT VS. SUPPLY
FAN SPEED
SAT HIGH SETPOINT
(Default = 65.0 °F)
SAT LOW SETPOINT
(Default = 55.0 °F)
Supply Fan Speed
%
FAN SPEED
FOR HIGH SAT
FAN SPEED
FOR LOW SAT
Active SAT
Setpoint
Increasing Supply Fan Speed
LD10308A
Return Air Based SAT Reset
This is the most popular operation. When the “SAT
RESET METHOD” is set to “RETURN AIR,” the con-
troller monitors the RETURN AIR TEMP and sets the
“ SUPPLY AIR TEMP ACTIVE SP” to a value between
the
“
SAT HIGH SETPOINT” and the “SAT LOW
SETPOINT.” If the RETURN AIR TEMP is equal to
or greater than the “RAT SETPOINT FOR LOW SAT,”
the “SUPPLY AIR TEMP ACTIVE SP” is the “SAT
LOW SETPOINT.” If the RETURN AIR TEMP is
equal to or less than the “RAT SETPOINT FOR HIGH
SAT,” the “ SUPPLY AIR TEMP ACTIVE SP” is the
“SAT HIGH SETPOINT.” When the RETURN AIR
TEMP is between the “RAT SETPOINT FOR HIGH
SAT” and the “RAT SETPOINT FOR LOW SAT,” the
“SUPPLY AIR TEMP ACTIVE SP” is linearly inter-
polated between the “SAT HIGH SETPOINT” and
the “SAT LOW SETPOINT” (see Figure 57 on page
111).