The General 800 humidifier is a whole house bypass style humidifier designed for residential and light commercial applications. It is mounted on the supply plenum. Since it is a very basic low capacity unit there is no humidistat. To control it you merely turn the water off in the spring and back on in the fall. Annual maintenance on the General 800 humidifier consists of replacing the humidifier plates two or more times per year and washing out the humidifier.