The Johnson Controls A19ABC-24C Remote Bulb Temperature Control is a specialist device used in HVAC systems to maintain exact temperature regulation between 30°F and 100°F. As a remote bulb temperature control with an 8-foot capillary tube, it detects temperature changes and regulates heating or cooling equipment using a Single Pole Double Throw (SPDT) switch. https://www.partshnc.com/a19abc-24c-johnson-controls-spdt-remote-bulb-temperature-control-30100f-8-cap-replaces-a19abc-24e-grain