Spectra
Pure
®
Inc.
215 S. Industrial Drive, Suite 2A Tempe, Arizona 85281-2941 480.894.5437 Fax us toll-free 1.877.527.7873
Call us toll-free 1.800.685.2783 E-mail [email protected] Visit us on the web www.spectrapure.com
13
Theory of Operation: Electronic Control System
The Reverse Osmosis System Controller (27) is the grey box on the front of the system.
Inside this box is a 24 VAC transformer, a power relay, and a microprocessor-based control
board. The transformer provides a safe voltage level for all control system functions. On
the front of the controller is the main power switch, system fuse (15 amp, slo-blow), and
two LEDs. The green LED blinks at a 1 second rate and indicates proper operation of the
control board. The red LED indicates error conditions. Currently, error conditions indicated
by the blinking red LED include: 1- fl oat switch faults and, 2- low feed water input pressure.
When water is withdrawn from the tank to a point below the low-level fl oat (or pressure
switch) (12) and the carbon fi lter cut-out switch is closed, the input solenoid (2) is activated.
When suffi cient feed-water input pressure is sensed by the input pressure switch (5), the
control board will activate the power relay which in turn will apply power to the main pump
(6) and motor (7). The pump / motor will boost the recirculating system pressure to 100-
110 psi.
If, at any time during a fi ll cycle, the input pressure drops enough to de-activate the input
pressure switch, the main pump and motor will be powered down. The control board will
then attempt two more start sequences. If low input pressure is detected two more times,
the system will shut down completely and indicate the condition by the red blinking LED.
The controller will need to be powered down and a determination as to the cause of the
persistent low pressure condition will have to be made.
A normal fi ll cycle will terminate when the water reaches the high-level fl oat (or pressure
switch) (13). A fl ush cycle will begin with the input solenoid and main pump continuing to
operate while opening the concentrate bypass solenoid (25). The fl ush cycle will terminate
after 45 seconds; the bypass solenoid is turned off and the pump and motor will spin down
before the input solenoid is turned off, protecting the pump from a starvation / cavitation
condition. For the next six minutes, the pure water fl ush pump (9) is activated, fl ooding the
membrane with a pure-water bath until the fi ll cycle starts over again.
