The Walchem W900 Series controllers are designed for flexible control in water treatment applications. They feature four slots for various Input/Output Modules, offering unparalleled versatility.
Function Description
The W900 Series controllers provide comprehensive control over water treatment processes. They support a wide array of sensor inputs, including contacting conductivity, electrodeless conductivity, pH, ORP, Walchem disinfection sensors, and generic sensors with linear voltage output. Analog input modules are available for 2, 3, or 4-wire transmitters. The controllers also feature analog output modules for retransmitting sensor signals to chart recorders, dataloggers, PLCs, or other devices, and for linear proportional or PID control of valves, actuators, or metering pumps.
Eight Virtual Inputs can be configured for calculations based on two real inputs or for redundancy by comparing values from two sensors. The controllers offer eight relay outputs with a variety of control modes, such as On/Off set point, Time Proportional, Pulse Proportional, Flow Proportional, PID, Lead/Lag (up to 6 relays), Dual set point, Timer, Bleed or Feed based on water contactor/paddlewheel flow meter input, Feed and Bleed (with or without Lockout), Feed as a percent of Bleed or elapsed time, Daily/Weekly/2-week/4-week Biocide timers (with pre-bleed and post-add lockout), Intermittent sampling for boilers, Always on (unless interlocked), Probe Wash timer, Spike to alternate set point, Target PPM, PPM Volume, Dual Switch, and Boolean Logic. Diagnostic alarms can be triggered by high/low sensor readings, no flow, relay output timeout, or sensor errors. Relays are available in combinations of powered, dry contact, and pulse solid-state opto relays. Eight Virtual Outputs can also be configured using various control algorithms to interlock or activate actual control outputs.
Standard Ethernet connectivity allows remote access for programming, emailing datalog files (CSV format), and alarms to up to eight email addresses. Modbus TCP and BACnet options facilitate communication with PC-based applications, HMI/SCADA programs, Building Energy Management systems, and Distributed Control Systems (DCS). Optional WiFi cards enable simultaneous Ethernet and WiFi communications or increased security by disabling Ethernet when WiFi is active. WiFi can operate in Infrastructure Mode (for Ethernet functions) or Ad-Hoc Mode (for wireless programming access). USB features allow for software upgrades, saving/importing configuration files, and data logging of sensor readings and relay activation events.
Important Technical Specifications
- Measurement Performance:
- pH: Range -2 to 16 pH units, Resolution 0.01 pH units, Accuracy ± 0.01% of reading.
- ORP/ISE: Range -1500 to 1500 mV, Resolution 0.1 mV, Accuracy ± 1 mV.
- Disinfection Sensors: Range -2000 to 1500 mV (mV) or 0-2 ppm to 0-20,000 ppm (ppm), Resolution 0.1 mV (mV) or varies with range and slope (ppm), Accuracy ± 1 mV (mV) or varies with range and slope (ppm).
- RTD Temperature (100Ω & 1000Ω): Range 23 to 500°F (-5 to 260°C), Resolution 0.1°F (0.1°C), Accuracy ± 1% of Reading or ± 1°C (100Ω) / ± 0.3°C (1000Ω), whichever is greater.
- Thermistor Temperature (10k or 100k): Range 23 to 194°F (-5 to 90°C), Resolution 0.1°F (0.1°C), Accuracy ± 1% of Reading or ± 0.3°C, whichever is greater.
- Analog (4-20 mA): Range 0 to 22 mA, Resolution 0.01 mA, Accuracy ± 0.5% of reading.
- Corrosion: Ranges 0-2, 0-20, 0-200 mpy or mm/year, Resolutions 0.001, 0.01, 0.1 mpy or mm/year, Accuracy ± 0.5% of reading.
- Contacting Conductivity: Cell constants 0.01, 0.1, 1.0, 10.0, with ranges up to 300,000 µS/cm and accuracies of ± 1% of reading or 0.01/0.1/1/10 µS/cm, whichever is greater.
- Electrodeless Conductivity: Ranges from 500-12,000 µS/cm to 200,000-2,000,000 µS/cm, Resolution 1-100 µS/cm, Accuracy 1% of reading.
- Electrical Input/Output:
- Input Power: 100 to 240 VAC, 50 or 60 Hz, 13 A maximum.
- Sensor Input Signals: 0 to 8 depending on model code, supporting various sensor types with temperature inputs (100/1000 ohm RTD, 10K/100K Thermistor).
- Analog (4-20 mA) Sensor Input: 0 to 24 depending on model code, supporting 2, 3, or 4-wire transmitters, fully isolated channels with available 24 VDC power.
- Digital Input Signals (12 standard): Optically isolated, 12VDC power, nominal 2.3mA current when closed, response time < 2 seconds, supporting isolated dry contacts (relay, reed switch).
- Outputs: Powered mechanical relays (0-8), dry contact mechanical relays (0-8), pulse outputs (0, 2, or 4) (opto-isolated, solid-state relay, 200mA, 40 VDC Max.), 4-20 mA outputs (0-16) (internally powered, 15 VDC, fully isolated, 600 Ohm max resistive load).
- Mechanical:
- Enclosure Material: Polycarbonate, NEMA 4X (IP65) rating.
- Dimensions: 12.2” W x 13.8” H x 5.4” D (310 mm x 351 mm x 137 mm).
- Display: 320 x 240 pixel monochrome backlit display with touchscreen.
- Operating Ambient Temp: -4 to 122 °F (-20 to 50 °C).
- Storage Temperature: -4 to 176°F (-20 to 80°C).
- Humidity: 10 to 90% non-condensing.
Usage Features
The W900 Series controllers are operated via a touchscreen interface. The Home screen displays user-defined input readings or output statuses, with automatic or manual toggling between groups of items. Touching an item brings up its Details Screen for calibration and settings. The Main Menu provides access to Alarms, Inputs, Outputs, Configuration, HOA, and Graph menus.
- Changing Numeric Values: Use the Character Delete icon, numeric touchpad, and decimal point. Confirm with the Confirm icon.
- Changing Names: Use the Move Cursor icon, Make Character Higher/Lower icons, and Enter icon.
- Choosing from a List: Scroll through options using Page Up/Down icons, highlight the desired option, and confirm.
- Hand-Off-Auto Relay Mode: Select Hand (forced on for a specified time), Off (always off), or Auto (responds to control set points).
- Interlock and Activate with Channels: Select digital inputs or relays to interlock or force activation of a relay.
- Initial Startup: After mounting and wiring, plug in and power on. The display shows the model number, then the Home screen.
- Configuration: Set language, date, time, global units, and temperature units via the Configuration Settings menu.
- Input Programming: Configure settings for each sensor input (type, cell constant, units, alarms, smoothing factor, default temperature, cable length, gauge).
- Sensor Calibration: Perform one-point process, one-point buffer, or two-point buffer calibrations. For disinfection and generic sensors, start with Zero Calibration; for electrodeless conductivity, start with Air Calibration.
- Output Programming: Configure control mode, set points, timer values, and interlock channels for each output.
- Graph Menu: Display graphs of sensor or analog input values, or digital input/relay states over various time ranges. Data points can be downloaded as CSV files for finer resolution.
- Ethernet Operation: Access all settings via a web browser by connecting to a LAN or directly to a computer. DHCP or fixed IP address configurations are supported. Default username is "admin" and password is the 10-digit serial number.
- Software Upgrade: Upgrade controller software via USB or Ethernet connection (if enabled and connected to the internet).
- Notepad Menu: Store up to 10,240 bytes of notes for important process changes or events.
Maintenance Features
The controller requires minimal maintenance.
- Cleaning: Wipe with a damp cloth. Do not spray with water unless the enclosure door is closed.
- Electrode Cleaning: Electrodes should be cleaned periodically. The frequency depends on the installation. A cleaning procedure is provided, involving a cloth or paper towel with mild detergent, or dilute hydrochloric acid for scale. Abrasive paper can be used for coated electrodes. Recalibration is required after cleaning.
- Fuse Replacement: Instructions are provided for replacing the fuse protecting powered relays. Only Walchem-approved fuses (5 x 20 mm, 6A, 250V; P/N 102834) should be used to maintain safety certifications.
- Troubleshooting: A dedicated section provides guidance for calibration failures (contacting conductivity, electrodeless conductivity, pH, ORP, disinfection, analog inputs, temperature, corrosion inputs) and alarm messages (HIGH/LOW, DEVIATION, DI STATE, TOTAL, FLOW VERIFY, OUTPUT TIMEOUT, RANGE, EVENT SKIPPED, SENSOR FAULT, INPUT FAILURE, BATTERY POWER LOW, SYSTEM TEMP LOW/HIGH, DISPLAY ERROR, ETHERNET CARD FAILURE, WEB SERVER FAILURE, FLUENT DATA COMM ERROR, SENSOR CAL REQUIRED, CALCULATION ERROR, MESSAGE ERROR, BOOLEAN ALARM, DAILY MAX TIMEOUT, FRAM FILE SYSTEM ERROR, REPLACE ELECTRODES, WiFi MODULE FAILURE, WiFi CONNECTION ERROR, UPDATE TIMEOUT, INVALID SENSOR TYPE, INVALID CONTROL MODE, FLUENT LIVE CONNECT ERROR, DISABLED, RELAY OR ANALOG OUTPUT CONTROL FAILURE).
- Diagnostic Lights: Information on LED indicators for the controller board and I/O boards helps diagnose software and hardware issues.
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