PHOTOHELIC SWITCH:
For applications that require a Photohelic switch to monitor filter loading and control the operation of
auto-cleaning, additional wiring must be performed.
1. An optional Photohelic switch is made available for the CAB unit. Additional electrical installation is
required for this option in order to allow the switch to control the automatic cleaning system while
monitoring the pressure drop across the cartridge filters. Before wiring may begin, first locate the
Photohelic switch kit and mount it to a suitable location. Run air lines from the Photohelic switch ports to
the CAB unit. (Refer to Photohelic switch installation instructions, Page 13).
2. Once the Photohelic switch has been physically installed, route electrical conduit from the electrical box
enclosure to the Photohelic switch.
3. Next, route 2 wires (16 AWG min.) from the Photohelic switch to the electrical box enclosure. Allow
adequate length of wire to reach the upper left corner of the timer circuit board terminal strip labeled
PRESSURE SWITCH (See PAGES 14-22 for Wiring Diagrams).
IMPORTANT: Solid state circuits are sensitive to electrostatic shock. Take measures to ensure
that minimal static charge is discharged before making adjustments or changes to wire
connections on the timer board.
4. Prior to making connections to the PRESSURE SWITCH terminal, disconnect the two wires connected
to the terminal and also disconnect the other ends of the red wires that are connected to an auxiliary
contact (switch) located on a motor starter relay. Discard wires for this installation.
5. Connect each wire from the Photohelic switch to each terminal on the timer board indicated as
PRESSURE SWITCH. Be certain that only one wire is connected to each terminal.
6. Move the enable/disable switch on the timer board to the DISABLE position. This will inactivate the off-
line cleaning feature of the timer circuit, which is more common when only demanding automatic
cleaning when filters reach a certain static pressure level.
7. After all wiring connections have been completed; close the electrical box enclosure, securing the
enclosure cover with screw clamps provided. By hand, turn the safety switch disconnect to the ON
position.
8. Photohelic settings are to be adjusted for optimized cleaning performance. Typically, a low setting at 2”
w.c. and a high setting at 3” or 4” is a recommended starting point. Once the pressure drop across the
cartridge filters reaches the upper limit of the gauge, the automatic cleaning system will engage and
continue to run until the static pressure drops below the lower setting.
NOTE: If the after-pulse (off-line pulse) switch is enabled, the cleaning system will continue to clean for
the duration of pulses upon reaching the lower limit setting noted above.
TIMER BOARD ONLY:
1. For applications that do not include a factory wired electrical box assembly (which includes timer, motor
starter(s), disconnect, etc.) a multi-channel timer PCB is supplied within a NEMA enclosure. Motor
starters and controls to start and stop the entire system are supplied by other means.
2. Before wiring, locate the timer board and enclosure in an appropriate mounting location that will allow
access for timer adjustments.
3. Run electrical conduit from solenoid valves located on the CAB unit(s) to the timer board enclosure.
4. Run wires from the timer board output channels to the solenoid valves (refer to Wiring Diagram,
PAGES 14-22).
IMPORTANT: Solid state circuits are sensitive to electrostatic shock. Take measures to ensure
that minimal static charge is discharged before making adjustments or changes to wire
connections on the timer board.
