The Walchem WCT400-5NNU controller is now obsolete and the closest equivalent is the WCT600 controller. The new WCT600 series has upgraded features; for reference, here is the description of the old model:
Cooling tower controller – bleed & feed, hardwired, cable glands, no 4-20 mA output, no electrode, integrated datalogging and config file import/export via USB flash stick.