NEMA 4X instrument Front
Flow proportioning control
Residual control
Compound loop flow pacing control
Dechlorination with sulfur dioxide
Feed forward/feedback control
Available in new Field Mount case


The 555 1/4 DIN Chlorination Controller provides the water and wastewater treatment industry an automatic and accurate means to control chlorine in potable and wastewater applications. The 555 can be easily set up to handle flow proportional control, residual control, compound loop control with lag times, and dechlorination with sulfur dioxide.
Flow paced (or flow-proportioning) control positions a chlorine or sulfur dioxide valve in direct proportion to the water flow rate. For chlorine, a user-defined "dosage-setting" from 0% to 400% (the percentage of gas flow to water flow) increases or decreases the rate of gas feed dependent on water flow rate. Flow paced is well suited where the water flow rate varies but the disinfection/oxidation demand remains constant.
Residual control positions a chlorine valve based on chlorine residual measurement. With a user defined residual setpoint, the 555 increases or decreases the gas feed dependent on deviation from setpoint. Residual control is ideal for applications where the water flow rate is constant but the disinfection/oxidation demand varies.
Compound loop control positions a chlorine valve based on chlorine residual measurement and water flow measurement. The residual control signal trims the valve position signal generated by flow proportional control. Compound loop control is ideal for applications where water flow rate and disinfection/oxidation demand vary, or where tight control is required.
Feed forward dechlorination control positions a valve (typically sulfur dioxide) in direct proportion to the water flow rate and residual level. With a user-defined "dosage-setting" from 0% to 400% (the percentage of gas flow to water flow) the 555 increases or decreases the rate of gas feed dependent on changes in residual level or water flow rate.