Greenheck RL147 Positioner Relay - Manual (Page 2)

Technical Instruction Landis & Gyr, Inc.
RL 147-2 Page 2
APPLICATION
The Positioning Relay is recommended for damper actuator
and valve applications where rapid speed of response and/or
repeatability of stem position is needed to obtain good system
operation. It can be used to reduce the span of controlled
devices to permit sequencing. It can also be used to increase
the close-off force of a normally open actuator without
affecting its spring span. This happens because the positioner
uses full supply air pressure to position the actuator.
The spring range of the actuator does not effect the operation
of the positioner. Therefore, it is recommended that an
actuator with a high spring range, such as 8 to 13 psig (55 to
90 kPa), be selected. This combination has the high return
force of the actuator spring plus the high forward force
available from the positioner.
A positioning relay can be connected to handle up to four
identical No. 6 damper actuators or up to six identical No. 4
damper actuators provided the following conditions are met.
All actuators must operate the same damper, and no more
than 100 feet of 1/4” (6.4 mm) O.D. tube is used to connect
them. Remember all actuators connected this way must be
identical (i.e., same size, spring range, stroke, etc.).
The positioning relay is single acting and is primarily intended
for use on actuators with an integral spring to return the
actuator shaft to the normal position. Applications with a
double acting (spring-less) actuator require a reversing relay to
provide the additional control signal.
OPERATION
A rise in thermostat pressure will unbalance the lever
assembly. Refer to Figure 2. The shaft movement, through the
spring arm, increases tension on the feedback spring to bring
the lever assembly again into balance. A drop in thermostat
pressure will unbalance the lever assembly in the opposite
direction to exhaust air from the actuator until a new balance
position is reached.
The positioning relay start point is adjustable. The start point
adjustment nut shown in Figure 2 is used to set the start point
pressure. The span adjustment screw tab location on the
feedback arm and the feedback spring location on the spring
guide determine the span setting of the relay.
Figure 2. Operation Schematic.