Walchem W900 Series Operating instructions

W900 Quick Programming Guide
Programming the W900 for Cooling Tower control (using keypad):
Conductivity sensor
Bleed Relay (Intermittent Proportional Control)
Feed Relay
Flow switch to lockout controls when no flow
To Confirm your controller is in HVAC mode.
1. From the Home screen, press Config
2. Select Global Settings
3. Press the DOWN Arrow until HVAC Modes is highlighted.
4. Press Enabled, and then .
Programming the Conductivity Sensor
1. From the Main Menu, press INPUTS
2. Select the sensor input that the conductivity sensor is wired to
3. Press
4. Press the DOWN Arrow until Type is displayed
5. Press Type
6. Use the DOWN Arrow to select Contacting Conductivity, and press the Check
Programming the relay for Bleed
1. From the Main Menu, press Outputs
2. Choose the relay for the blowdown valve
3. Press Configuration
4. Press the DOWN Arrow until Mode
5. Press Mode and choose On/Off and press the Check
6. Press Configuration again
7. Press the DOWN arrow until you see Input
8. Press Input, and then select the Conductivity sensor. Press Check
9. Press UP or DOWN Arrow, then HOA Setting. Select AUTO
You’ve now programmed the relay for the blowdown valve, and programmed the sensor, and assigned
it to that relay.

W900 Quick Programming Guide
Programming Inhibitor Feed
1. From the main menu, press Outputs
2. Select the relay you want to use for the inhibitor feed pump
3. Press Configuration
4. Press the DOWN Arrow until you get to MODE
5. Choose the feed mode you want, and then Check
6. Press Configuration again.
7. If you set the mode for Bleed and Feed, press the Down Arrow until you get to Bleed
8. Press Bleed, and then select the relay that has been programmed for the bleed valve.
9. Press Check
10. Press the UP or DOWN Arrow, then HOA setting. Select Auto
Programming Biocide Additions
1. From the main menu, press Outputs
2. Select the relay you want to use for the biocide pump.
3. Press Configuration
4. Press the Down Arrow until you get to Mode
5. Select Biocide Timer, and Check
6. Press Configuration
7. Press Event 1
8. Screen should say Repetition None. Press this.
9. Using the Down arrow, you can choose Daily, 1 Week, 2 Week or 4 Week.
10. When you press Daily, you will be prompted to enter a Start Time, and the Duration. This event will
repeat every day. If you want more than one event per day you can add additional events. Just press
Event 2 to Event 10 to program. When you press 1 Week you will be prompted to enter a day of the
week, start time and duration. Again, you can repeat this on events 2-10 if you want more events
repeating every week. You can also enter events based on a 2 week and 4 week timer.
11. After the events have been programmed, you can press the down arrow to program a pre-bleed,
bleed lockout, as well as interlocking other channels.

W900 Quick Programming Guide
Programming a flow-switch interlock (digital input)
1. From the Main Menu press Inputs
2. Press the DOWN arrow until you get to the desired digital input
3. Press
4. DOWN Arrow until Type
5. Press Type, then DI state
6. Press again. In this menu you choose when to interlock: Open or Closed. You can also
choose a custom message for when the switch is open and closed.
7. In each relay menu, you can choose which inputs you want to interlock with.