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R7426A,B,C,D TEMPERATURE AND UNIVERSAL INPUT CONTROLLERS
IO1
Xp
CTRP1
CTRP2
SUBMASTER
W
LIM
1
2x
W
CAS
R
CAS
2
W
LIM
1
WHEN LimTyp IS 1.
2
Fig. 6. Occupied Cascade Control.
— CTRP2 high limit is performed if parameter LimTyp is 1.
— CTRP2 low limit is performed if parameter LimTyp is 0.
Economizer Modes
Economizer modes are suitable for installations where the
main temperature sensor (I01) is installed in either exhaust air
or the room with a constant offset between room and exhaust
air conditions. The offset value is programmable within 0°F to
9°F with parameter RetOffs which will be added to the actual
room temperature value to simulate exhaust air conditions.
NOTE: Economizer mode is disabled if parameter RetOffs is
programmed Off, or no OAT sensor is connected.
By comparing the conditions of outside air with exhaust air,
the O1 output on the three-output controller operates using
Mixed Air Dampers or an Energy Recovery System:
Economizer Mixed Air Damper Mode
Economizer mixed air damper mode is active when:
• RetOffs is not Off.
• DIR/REVO1 is Dir.
NOTE: See Table 3 for control logic.
Table 3. Economizer Mixed Air Damper Mode.
Outside Air Temperature
Greater than exhaust air
temperature
Less than exhaust air
temperature
NOTE: A fixed hysteresis of 2°F is used to switch between
MINPOS and O1.
Economizer Energy Recovery System
Economizer mixed air damper mode is active when:
• RetOffs is not Off.
• DIR/REVO1 is Rev.
63-2565
MASTER
0
Xw MASTER
0
Xw MASTER
WHEN LimTyp IS 0.
M17448
O1
MINPOS
Included in direct acting
heating sequence control
NOTE: See Table 4 for control logic.
Table 4. Economizer Energy Recovery System Mode.
Outside Air Temperature
Greater than exhaust air
temperature
Less than exhaust air
temperature
NOTE: A fixed hysteresis of 2°F is used to switch between
100 percent and O1.
Controller Functions
Outside Air Temperature Compensation
Outside air temperature compensation is performed when I03
is connected. The parameter W
winter compensation changeover point. Parameters Wi and
Su define the degree of summer and winter compensation.
CTRP1
W1+XOFFS+CPA
M17451
Fig. 7. OAT Compensation.
When Dir/RevO1 = Rev (heating control):
When Dir/RevO1 = Dir (cooling control):
• Winter compensation is performed if
• Summer compensation is performed if
SMOOTHING FILTER FOR OUTSIDE AIR TEMPERATURE INPUT
A smoothing filter for OAT input I03 is incorporated to
eliminate sudden temperature variations. This provides more
stable control system operation.
Summer/Winter Changeover Function
Occupancy input can alternatively be used for summer/winter
changeover. Activate the summer/winter changeover function
by setting the control parameter DIR/REVO1 to Cho .
NOTE: This is provided only on the R7426A controller.
A potential free contact can be used between terminals 1 and
4 to switch the controller mode to heating (contact open) or
cooling (contact closed).
Freeze Protection
See Table 5 for actions executed when the contact connected
to the freeze protection input is opened. A closed contact
performs frost recovery (see Table 6).
NOTE: Freeze protection operation takes priority over all
other control operations.
6
O1
100 percent
Energy Recovery System
included in heating sequence
control. MINPOS is not active.
defines the summer and
comp
Wi
Su
W comp
IO3
XOFFS
=
–
OFFS
XOFFS
=
OFFS
<
I03
W
.
COMP
>
I03 W
COMP
.
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