Honeywell T991A1012 Proportional Temperature Control 0°F-100°F 20' Capillary

The Honeywell T991A1012 is a proportional temperature controller designed to regulate water or air temperature in a variety of HVAC applications. It contains a 20-foot-long capillary tube for remote temperature detection with a temperature range of 0 to 100 degrees Fahrenheit. This control operates by the use of a capillary loaded with liquid. The liquid expands in response to rising ambient temperature, applying pressure to a diaphragm inside the control. Depending on the application, this pressure change prompts the control to modify the hot water or airflow to maintain the appropriate temperature setting. The Honeywell T991A1012, which is commonly found in radiant heating panels, boilers, and hydronic heating systems, has several advantages.