DAMPER ACTUATOR (MOTOR) WITH POSITIVE POSITIONING RELAY Damper actuators with no positive positioning (pilot positioner) relay often position the damper at a different degree of opening for the same pressure when the pressure is increasing to that pressure or decreasing to that pressure. As the damper increases its frictional impact with dirt and age, positioning will be different for the same pressure relative to when the damper was new. Positive positioners present three benefits: -1- The throttling range of the controller is adjustable. On the old Honeywell the six screws under the round cap allowed selection of three, five or ten pound ranges. The position of the spring connected to the linkage from the shaft allows span adjustment for Johnson Controls, Barber Colman and SIEMENS positive positioners. The feedback springs can be changed to have three, five and ten pound spans on the new Honeywell, Kreuter and Robertshaw positive positioners. -2- The feedback spring allows the positioner to “know” the percentage of stroke, regarding the actuator’s shaft, at all times. The positive positioner will apply air pressure to the actuator’s diaphragm from main air pressure to zero PSIG maintaining the damper exactly at the percentage of stroke demanded by the controller. The start point for the stroke is adjustable. -3- Positive positioners boost a low volume signal to a high volume signal. DIAPHRAGM CUP ACTUATOR HOUSING CAP ACTUATOR HOUSING RETURN SPRING SHAFT AIR CONNECTION DIAPHRAGM POSITIVE POSITIONER POSITIVE POSITIONER’S FEED BACK SPRING SIGNAL MAIN AIR CONTROLLER SIGNAL 2.11
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