Chemtrol a Division of Santa Barbara Control Systems

- Model 255 - PPM/pH Controller



The Chemtrol 255 PPM/pH Digital Controller introduces the new sensor for Free Chlorine control in automated water treatment.A microprocessor-based digital controller, it is designed to maintain both free chlorine PPM and water pH in high-end residential pools, small commercial pools and spas and light industrial applications.Unlike other chlorine sensors on the market, these sensors are easy to installl and maintain, very precise and so reliable that they are covered by a full 2-year warranty.For better water management results, it is recommended to use ORP control of chlorine oxidizing activity and PPM monitoring of free chlorine. Alternatively, PPM control can be used for control of the sanitizer and ORP control for an oxidizing agent, such as ozone.

A simple and inexpensive controller for:

  • Residential Pools and Spas
  • Commercial Pools and Spas
    • Hotels, Motels
    • Health Clubs
    • Apartments Buildings
    • Condo Associations.
  • Industrial Water Treatment.


The new Free Chlorine Sensor is a solid state sensor with a selective membrane that provides direct readings of Free Chlorine in water at concentrations ranging from 0.1 to 10 ppm (parts per million) or mg/l (milligrams per liter).

These are true readings of Free Chlorine corresponding to the DPD #1 test.

A significant advantage of this sensor is that it's not affected by cyanuric acid (CYA) stabilizer and/or oxidizers, thereby assuring constant Free Chlorine levels at all times. Extensive laboratory and field tests have shown it to be very accurate and reliable.

As shown on the graphic data log on the right, the new sensor gives the operator precise and reliable control of Free Chlorine under the most difficult conditions.

The CHEMTROL® 255 is the only easy-to-use controller offering Free Chlorine and pH control for pools, spas, cooling towers, industrial water treatment, etc.

Designed for affordability, simplicity of installation, ease of use and long-term reliability, it includes features normally not found on this type of controller, such as:

• adjustable setpoints,

• adjustable high and low alarms,

• adjustable overfeed safety timers and

• adjustable proportional feed control.

  • Easy to install
  • Simple to use
  • All Control Functions on Front Panel
  • Separate Adjustable Setpoints
  • Separate Adjustable Alarms
  • Acid/Base Selector
  • Proportional Feed with Adjustable Bandwidth
  • Separate Adjustable Overfeed Safety Timers
  • Waterproof Cabinet with Clear Window Cover
  • 5-year Electronics Warranty
  • Toll-Free Technical Support


Unlike conventional amperometric or colorimetric sensors, the PPM sensor is easy to install and operate. It does not require a special pressure flow cell and/or expensive and expendable chemical reagents. And best of all, it’s maintenance free.

Installation of the CHEMTROL® 255 is as easy as 1-2-3.

  1. CONTROLLER - Connect the controller to the 110 or 230V output of the Timer in parallel to the recirculation pump.  This will prevent accidental feeding of chemicals when the pump is not running. Make sure to follow the electrical code.
  2. SENSORS - Install the PPM and pH sensors on the recirculation line or on the optional bypass line.  The two sensors can be mounted directly on the main recirculation line with 2' PVC tees, as shown on the schematic.  For recirculation lines over 2' in diameter lines, the sensors should be mounted on a 1/2' bypass line.
  3. CHEMICAL FEEDERS - Connect the chemical feeders to the 110 or 230V controller outputs, according to the manufacturer's instructions, making sure to inject the chemicals downstream of the sensors.  For a bromine or chlorine erosion feeder, install a corrosion-resistant solenoid valve on the intake line of the feeder.  The controller is compatible with most ozonators and electrolytic generators.

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