Chemtrol CH255 PPM/pH Digital Controller – Free Chlorine & pH Control

The Chemtrol CH255 PPM/pH Digital Controller offers accurate and dependable automation of free chlorine (PPM) and pH levels for pools, spas, cooling towers, and industrial water systems. Its unique solid-state chlorine sensor measures true free chlorine directly (including HOCl, OCl⁻, and stabilized isocyanurates), and operates independently of cyanuric acid levels—unlike amperometric or colorimetric systems that require chemical reagents or high-pressure cells.

Built for ease of use and long-term performance, the CH255 features dual digital control channels for precise pH and sanitizer regulation, and includes adjustable setpoints, proportional feed, alarms, calibration menus, and full front-panel operation. The unit supports programmable 4–20 mA dual-channel output and includes Ethernet/Internet communication capability for remote support.

Installation is simple thanks to its included low-pressure flow cell, pH and PPM sensors (with 10-ft cables), and rotary paddle safety flow switch. The CH255 is housed in a splash-resistant polystyrene cabinet and carries an industry-leading 5-year electronics warranty.

Key Features

• True Free Chlorine control: 0.1–10.0 ppm standard (0.02–2.0 ppm optional)

• Solid-state PPM sensor unaffected by CYA or oxidizers

• 0.0–14.0 pH control via glass electrode

• Manual, automatic, or proportional feed modes

• Fully adjustable: setpoints, calibration, limits, and feed rate

• Front panel operation with LED readouts and status indicators

• Overfeed protection, out-of-range alarms, acid/base selector

• Dual 4–20 mA programmable output (PID ready)

• Rotary paddle flow switch for feed safety

• Ethernet port for remote communication and support

• 5-year electronics warranty / 2-year PPM sensor / 1-year all other parts

• UL and NSF 50 approved

What’s Included

• CH255 digital controller unit

• Free Chlorine PPM sensor with 10-ft (3 m) cable

• pH sensor with 10-ft (3 m) cable

• Rotary flow switch

• Flow cell assembly (low-pressure type)

• Installation and operation manual

Chemical feed pumps and mounting backboard sold separately.

Specifications

• Free Chlorine Control Range: 0.1–10.0 ppm (0.02–2.0 ppm optional)

• pH Control Range: 7.0–8.0 (adjustable)

• Feed Modes: Manual, automatic, proportional

• Display: LED – 3-digit PPM, 2-digit pH

• Sensors:

  • PPM: Solid-state sensor with selective membrane

  • pH: Glass electrode, 10-ft (3 m) cable

• Electrical: 110 V, 230 V, or 24 VAC (specify at order)

• Cabinet Dimensions: 9″ × 7″ × 4″ (22 × 18 × 10 cm)

• Shipping Dimensions: 12″ × 12″ × 12″ (30 × 30 × 30 cm)

• Weight: 9 lbs (4 kg) without pumps; 18 lbs (8 kg) with pumps

• Certifications: UL Listed, NSF 50 Approved

• Warranty:

  • Electronics: 5 years

  • PPM Sensor: 2 years

  • All Other Parts: 1 year

Visit Chemtrol for complete information.