R7426A,B,C TEMPERATURE CONTROLLER
19
63-2564—1
Start Point: O
start
(P.15)
O
start
determines the output O1 midrange shift from the
calculated control point.
O
start
is available on the single output R7426A and the
R7426B when the three floating outputs are configured for
OMode = 1.
Calibrate O
start
in degrees Fahrenheit. It is equal to the offset
(plus or minus) from the set values or calculated control points
at which O1 is at 50 percent.
NOTE: In P+l control, the start point should be set at zero.
Occupied/Unoccupied Function: SOFFS (P.16)
A potential free contact can be used between terminals 1 and
4 to switch between occupied (contact closed) and
unoccupied (contact open) modes.
Control point calculation:
• Occupied mode: Use temperature setpoint (W1).
• Unoccupied mode: SOFFS parameter value is added to
(cooling) or subtracted from (heating) the calculated control
point.
• Heating and cooling sequence applications: SOFFS value
is added to cooling control point (CTRPC) and subtracted
from heating control point (CTRPH). See Fig. 21.
IMPORTANT
Set R7426A parameter O1CTRF to 0 or 1 to match
the required application. If parameter O1CTRF is 2
(summer/winter changeover), SOFFS is ignored.
Fig. 21. Sequence control occupied/unoccupied function.
Return Air Offset: RetOffs (P.20)
Parameter RetOffs is available on R7426B,C controllers
only
.
For mixed air damper or energy recovery system control, it
activates
Economizer
mode when On.
NOTE: With the main temperature sensor (I01) installed in
the return air, set RetOffs to 0.
With the main sensor installed in the room and with a constant
offset between room and return air conditions, this offset value
can be adjusted from 0°F to 10°F using RetOffs. This value is
added to the measured room temperature to simulate return
air conditions.
When RetOffs is programmed to Off, or with no OAT sensor
connected,
Economizer
mode is disabled.
RuntimeO1, O2, O3 (P.21,P.22,P.23)
Parameters RuntimeO1,O2,O3 are available on R7426A,B
controllers
only
.
For three-position floating actuator control, the controller
converts the deviation signal to a proportional output pulse.
This pulse drives the actuators based on the Runtime value.
An automatic synchronization function ensures correct
actuator positioning. Synchronization run time is derived by
multiplying Runtime by 1.25.
By selecting pwm mode for output O1 or O3, the pwm output
(suitable for driving electric heat current valves) is controlled
from the heating signal. Interval and total cycle time is set by
the parameter RuntimeO1 or RuntimeO3.
Night Cycle: NightLow and NightHigh (P.24/P.25)
Parameters NightLow and NightHigh are used by the night
cycle program (controller mode is Off).
NOTE: Disable this function by setting these parameters Off.
Night Mode Offset: NOFFS (P.26)
This control parameter is used to set the night mode offset.
During night mode, freeze protection is active and the
occupied/unoccupied function is disabled.
• Night Mode: NOFFS parameter value is added to (cooling)
or subtracted from (heating) the calculated control point.
• Heating and cooling sequence applications: NOFFS value
is added to cooling control point (CTRPC) and subtracted
from heating control point (CTRPH). See Fig. 21.
O(%)
T
100
M17454
OFFS
OFFS
CTRPH
CTRPC
UNOCCUPIED
OCCUPIED
XpC
XpH
XpH
XpC