What triggers a condensate pump?

A residential HVAC condensate pump is triggered and activated mechanically by an internal floating switch mechanism located inside the plastic collection reservoir tank. As moisture drips continuously from your indoor evaporator coil down into the reservoir tank, the water level rises gradually until it reaches a specific, engineered activation fill line. This rising water lifts a small, lightweight plastic float arm upward along a vertical shaft; once the float reaches the designated threshold, it trips an internal electrical microswitch that closes the circuit, immediately powering on the electric motor to pump the accumulated water out through the discharge tubing before dropping back down to shut the motor off. You can troubleshoot float movement easily. You can verify that the trigger mechanism is healthy when manual water tests cause the float to rise and engage the motor smoothly.