Honeywell AUTOMATIC CONTROL, Engineering Manual

Page: 123 / 518

ENGINEERING MANUAL OF AUTOMATION CONTROL
ELECTRIC CONTROL FUNDAMENTALS
113
W R B
W R B
T1
T2
ACTUATOR
DPDT
SWITCH,
RELAY, OR
THERMOSTAT
THERMOSTAT
TRANSFORMER
LINE
VOLTAGE
C2531
HEATING
COOLING
W R B
W R B
T1
T2
COOLING
ACTUATOR
SPDT SWITCH
CONTROLLER
TRANSFORMER
LINE
VOLTAGE
W R B
T1
T2
HEATING
ACTUATOR
TRANSFORMER
LINE
VOLTAGE
C2532
H
C
LINE
VOLTAGE
TRANSFORMER
W R B
W R B
T1
T2
W R B
T1
T2
W R B
T1
T2
CONTROLLER
SHUNTING
RESISTOR
ACTUATOR ACTUATOR ACTUATOR
C2533
LINE
VOLTAGE
W R B W R B
W R B
T1
T2
MINIMUM POSITION
POTENTIOMETER
135 135
CONTROLLER
DAMPER
ACTUATOR
TRANSFORMER
C2534
Fig. 30. Circuit Used for Reversing
Heating and Cooling Control.
Transferring Controller from
One Actuator to Another
Figure 31 illustrates a circuit which allows a single controller
to control two Series 90 actuators, one at a time. With the 3pdt
switch in the Cooling (C) position, the circuit connects the
controller to the cooling actuator with B to W and W to B. The
cooling actuator operates under normal control of the controller.
At the same time, the manual switch causes R to W to connect
at the heating actuator, positively closing it. With the switch in
the Heating (H) position, the controller is connected B to B
and W to W to the heating actuator which operates normally
and the cooling actuator is positively closed by a R to W
connection at the actuator.
Fig. 31. Circuit for Transferring Controller from One
Actuator to Another.
UNISON CONTROL
Figure 32 illustrates a circuit for controlling up to six
Series 90 actuators in unison from one Series 90 controller.
The B to W terminals of the controller are shunted with the
appropriate value resistor, depending on the number of
actuators in the circuit. This method can control a large bank
of dampers requiring more torque than can be provided from
a single actuator.
Fig. 32. Actuators Controlled in Unison
from One Controller.
MANUAL MINIMUM POSITIONING OF OUTDOOR
AIR DAMPER
Figure 33 illustrates a circuit for a typical outdoor air damper
control system with a manual potentiometer for minimum
positioning. Adjusting the potentiometer so that the wiper is at
W shorts the potentiometer coil out of the circuit and the outdoor
air damper actuator operates normally. The damper closes
completely if commanded by the controller. Moving the
potentiometer wiper toward B increases the resistance between
B on the controller and W on the actuator to limit the travel of
the actuator toward closed. The damper remains at the set
minimum position even though the controller is trying to close
it completely.
Fig. 33. Manual Minimum Positioning
of Outdoor Air Damper.