Condensate pumps usually run intermittently and have a tank in which condensate can accumulate. Eventually, the accumulating liquid raises a float switch energizing the pump. The pump then runs until the level of liquid in the tank is substantially lowered. Some pumps contain a two-stage switch. As liquid rises to the trigger point of the first stage, the pump is activated. If the liquid continues to rise (perhaps because the pump has failed or its discharge is blocked), the second stage will be triggered. This stage may switch off the HVAC equipment (preventing the production of further condensate), trigger an alarm, or both.