Barber-Colman TC-5131 Low Temp Duct Thermostat SPDT 2-Pos Auto Reset 34-60F

Barber-Colman TC-5131 Low Temp Duct Thermostat SPDT 2-Pos Auto Reset 34-60F

The Barber-Colman TC-5131 is a low temperature duct thermostat — commonly called a freeze stat — designed to sense air temperature inside an HVAC duct or air handling unit and switch a control circuit when the temperature drops to a preset level. It uses a 2-position, SPDT (single-pole, double-throw) switching action with automatic reset, meaning the contacts return to their normal position automatically once the temperature recovers above the setpoint. The unit features a long capillary sensing element that spans across the duct to average temperature across the air stream rather than sensing a single point.

Specifications & What's Included

• Model: TC-5131
• Manufacturer: Barber-Colman Co.
• Type: Low Temperature Duct Thermostat (Freeze Stat)
• Switch Action: 2-Position, SPDT (Single-Pole, Double-Throw)
• Reset Type: Automatic Reset
• Temperature Range: 34–60°F (0–16°C)
• Element: 20°F capillary sensing element
• Mounting: Duct-mounted via capillary bulkhead fitting
• Setpoint Dial: Graduated in both °C and °F, adjustable pointer visible on front panel
• Includes: Long coiled capillary sensing element and bag of metal duct mounting clips

Applications

Low temperature duct thermostats like the TC-5131 are a standard component in commercial and industrial HVAC systems. They are typically installed in the supply air duct downstream of a heating coil or heat exchanger to protect against freeze-up — if the air temperature drops below the setpoint (indicating coil freezing conditions), the thermostat trips the control circuit to shut down the air handler, close dampers, or trigger an alarm. The 20°F averaging element threads back and forth across the duct cross-section so the device responds to the coldest zone in the air stream rather than a single spot. Barber-Colman (later acquired by Invensys and now part of Schneider Electric's building controls portfolio) was a major supplier of HVAC controls and thermostats from the mid-twentieth century through the 1990s; their TC-series duct stats were widely specified in commercial building projects of that era and are still found in legacy building automation systems requiring replacement parts.