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R7426 Temperature Control
Depending on the deviation signal, the control output (O1)
value is calculated and converted to a floating signal. Select
direct or reverse action using the DIR/REV parameter (cooling
is Dir, heating is Rev). The throttling range setting (Xp1)
controls the output span.
The startpoint O
determines the midrange shift of the
start
output (O1) from the calculated setpoint (CTRP1).
Limit Control (W
, Xp2 and tr2)
lim
The R7426 controller offers limit control (W
the deviation signals of the main and limit control loops. The
lowest (low limit control) or highest (high limit control)
deviation signal is selected and fed to the output stage.
High limit control is performed when parameter LimTyp is 1.
Low limit control is performed when parameter LimTyp is 0.
During limit control, throttling range (Xp2) and reset time (tr2)
are active.
NOTES: Limit control is active only if either:
—
I02 temperature sensor (parameter I02ext is 0) is
connected, or
—
I01 sensor (control parameter I02ext is 1)
supplies the control loop.
Cascade Control (W
The R7426 provides cascade control using two control loops
(master and submaster) to maintain setpoint (CTRP1).
At zero room temperature deviation (X
temperature (I02) is controlled by the programmed setpoint
(W
= CTRP2). If room temperature deviates, submaster
cas
setpoint (CTRP2) is altered. See Fig. 4.
— Reset span adjustment (R
effect.
— Integral reset time and throttling range of submaster P+I
control can be adjusted with tr2 and X
— CTRP2 high limit is performed if LimTyp is 1.
— CTRP2 low limit is performed if LimTyp is 0.
IO1
Xp/2
Offs
CTRP1
Offs
Xp/2
CTRP2
SUBMASTER
W
LIM
1
W
2x
CAS
R
CAS
2
W
LIM
1
WHEN LimTyp IS 1.
2
Fig. 4. Cascade control.
NOTES: Offs varies depending on the control mode:
—
Occupied: Offs is 0. (See Fig. 6.)
—
Unoccupied: Offs is SOFFS.
—
Night: Offs is NOFFS.
R7426A,B,C,D TEMPERATURE AND UNIVERSAL INPUT CONTROLLERS
) by comparing
lim
, R
and tr2)
cas
cas
Master), discharge
W
) determines degree of reset
cas
p
2 .
MASTER
0
Xw MASTER
0
Xw MASTER
WHEN LimTyp IS 0.
M17450
R7426B,C Control with Heating, Mixed Air
Dampers and Cooling
Sequence Control
This application will be active with the R7426B,C controllers
when I02 is not connected. It can be used for sequence
control of a heating valve, an energy recovery system or a
mixed air damper and a cooling valve.
The characteristic of each output can be selected via the
parameters DIR/REVx (where x is O1, O2 or O3). Fig. 5 shows:
• Dir characteristic for all outputs.
• Control of damper signal within the range Xp1.
NOTE: If no cooling actuator is available, the parameter Xpc
can be set to Off and damper output is maintained at
100 percent above control point (CTRP1).
If damper output should be descreased to MINPOS level
above CTRP1 (see Fig. 5), or if no cooling actuator is
available, parameter Xpc must be adjusted to a value
between 2°F and 72°F.
O1
REV
100%
0
Fig. 5. R7426B,C direct/reverse action.
Temperature Cascade Control
This application will be active with the R7426B,C controllers if
parameter W
is set to any value other than Off. It can be
cas
used for sequence control of: a heating valve, an energy
recovery system, or mixed air damper and cooling valve.
Three cascade control modes are available:
• With occupied (contact closed) mode. (See Fig. 6.)
• With unoccupied (contact open) mode. See Cascade
Control section (Fig. 4).
• With night mode. See Cascade Control section (Fig. 4).
Each output characteristic can be selected via parameters
DIR/REVx (where x is O1, O2 or O3). Fig. 5 shows:
• Dir characteristic for all outputs.
• Control of damper signal within the range Xp2.
NOTE: If no cooling actuator is available, the parameter Xpc
can be set to Off.
If parameter Xpc is Off, the cooling signal is set to 0 percent
and damper output is maintained at 100 percent above control
point (CTRP1).
5
DIR
0
Xw
IO1
CTRP1
Y
START
M17447
Xp1
63-2565
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