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R7426A,B,C TEMPERATURE CONTROLLER
63-2564—1
6
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.
Fig. 5. R7426A cooling or heating control output.
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
cas
, R
cas
and tr2)
The R7426A provides cascade control using two control loops
(master and submaster) to maintain setpoint (CTRP1).
At zero room temperature deviation (X
W
Master), discharge
temperature (I02) is controlled by the programmed setpoint
(W
cas
= CTRP2). If room temperature deviates, submaster
setpoint (CTRP2) is altered. See Fig. 6.
— Reset span adjustment (R
cas
) determines degree of reset
effect.
— Integral reset time and throttling range of submaster P+I
control can be adjusted with
tr2
and
X
p
2
.
—
CTRP2
high limit is performed if
LimTyp
is 1.
—
CTRP2
low limit is performed if
LimTyp
is 0.
Fig. 6. Occupied cascade control.
R7426B,C Control with Heating, Mixed Air
Dampers or Energy Recovery and Cooling
Standard 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.
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) (see Fig. 8).
If damper output should be reduced to MINPOS level above
CTRP1 (see Fig. 8), and if no cooling actuator is available,
parameter Xpc must be adjusted to a value between 2°F and
72°F.
CAUTION
Equipment Damage Hazard.
Can damage the controller beyond repair.
Keep floating output load below 450 mA.
On the R7426C controller the characteristic of each output
can be selected via the parameters DIR/REVx (where x is O1,
O2 or O3). See Fig. 8 for Dir characteristic for all outputs.
Temperature Cascade Control
This application will be active with the R7426B,C controllers if
parameter W
cas
is set to any value other than Off. It can be
used for sequence control of a heating valve, an energy
recovery system, or mixed air damper and cooling valve.
Two cascade control modes are available:
• With occupied (contact closed) mode. (see Fig. 6).
• With unoccupied (contact open) mode. (See Fig. 7.)
— CTRP2 high limit is performed if parameter LimTyp is 1.
— CTRP2 low limit is performed if parameter LimTyp is 0.
Fig. 7. Unoccupied cascade control.
NOTES:
• The Offs value varies with the control modes:
— Occupied: Offs is 0.
— Unoccupied: Offs is SOFFS.
— Night: Offs is NOFFS.
• See Fig. 8 for damper control signal within the range
Xp1 or Xp2 for cascade control.
M17735
CTRP2
MASTER: C MODE = OCCUPIED
P/P+I CONTROL
CTRP1
I01
1
1
2
3
3
IF LimTyp IS 1.
IF LimTyp IS 0.
CTRP1 = W1 – SOFFS (HEATING); CTRP1 = W1 + SOFFS (COOLING).
2
W
2x
R
W
CAS
CAS
LIM
W
LIM
Xp1
M17737
CTRP2
MASTER: C MODE = UNOCCUPIED
P CONTROL
1
2
W
2x
R
W
CAS
CAS
LIM
W
LIM
SOFFS SOFFS
CTRP1
I01
1
2
IF LimTyp = 1.
IF LimTyp = 0.
Xp1/2
Xp1/2