Analog Differential Pressure VAV Controller-Actuator

The compact analog electronic CSP-4702 is a combination controller-actuator designed primarily for use on pressure-independent VAV (Variable Air Volume) terminal units. It also has applications as an electronic static pressure controller. Differential air pressure is sensed by an internal digital CMOS sensor connected via 1/4" FR tubing to an SSS-1000 series airflow sensor. The 0 to 2" wc (0 to 500 Pa) differential pressure sensor is internally linearized and temperature compensated for high accuracy down to very low pressures.

The CSP-4702 offers full-range flow control of VAV terminal units when used with the CTE-5202 electronic room thermostat. (For sample applications with that thermostat, see the CTE-5202 Applications Guide.) Air flow control limits may be set at the thermostat or internal to the CSP-4702. An adjustable mechanical stop is also included.

The CSP-4702 accepts a 2 to 10 VDC control signal from the thermostat. “Anti-jitter” circuitry significantly reduces hunting and needless wear on the actuator and damper components (from unnecessary miniscule position changes caused by undamped analog input signals). It also provides a 16 VDC output supply to power the thermostat and a 1 to 5 VDC voltage output that is proportional to the sensed differential pressure.

The CSP-4702 mounts directly to 1/4- to 5/8-inch (6 to 16 mm) round shafts or 1/4- to 7/16-inch (6 to 11 mm) square shafts, eliminating the need for expensive and complicated linkages. A non-rotation bracket, to prevent lateral movement, is included. For troubleshooting and setup, internal status LEDs (under the cover) indicate green for opening and red for closing. Factory-set clockwise rotation-to-close can be reversed by changing a jumper position. A gear disengagement button allows easy manual positioning of the actuator.

NOTE: Air flow volume is determined from the differential pressure by the formula Volume (in "cfm") = the K factor of the VAV box multiplied by the square root of the differential pressure (in "wc"). The K factor should be in the information supplied by the VAV box’s manufacturer.