Float Switch R Wiring Stops Overflow Damage Wiring a thermostat R terminal through a float safety switch prevents drain pan overflow by cutting twenty four volt power to the HVAC system when a float detects high condensate, protecting homes from water damage and costly repairs. This guide explains float switch installation tips, low voltage wiring best practices, thermostat safety interlock placement, and how to test the float and control board response. Common search terms included are float sw