Product Specifications

Moisture Resistant Temperature Control

The 39T series of 1/2” (13mm) bimetal disc temperature controls from Therm-O-Disc® offers proven reliability in a moisture resistant sealed design. The snap action of the bimetal disc provides high-speed contact separation resulting in excellent life cycle characteristics. The sealed design provides moisture resistance for moisture prone environments. A variety of lead wire and mounting configurations are available to provide maximum design flexibility. The 39T has been specifically designed to permit easy mounting onto copper or aluminum tubing with excellent retention and thermal response. The stainless steel mounting bracket has been designed to accommodate a wide range of tubing sizes without the need to modify the control platform. The most popular applications include: refrigeration defrost termination and ice cube maker control. It is also applied in a range of heat pump and air conditioning applications.

Features and Benefits:

• Sealed construction provides moisture resistance for moisture prone environments.

• High-speed contact separation ensures long contact life.

• A variety of lead wires and mounting options provide excellent design flexibility.

• All materials have been selected to pass the refrigeration industry’s odor and taste tests.

• Statistical process control of manufacturing assures high product quality levels.

• Controls are 100% operation tested.

Switch Actions and Typical Applications:

The 39T is an automatic reset (SPST) switch. The switch can be built to either open or close its electrical contacts on temperature rise or fall. Once the temperature in the application has returned to the specified reset temperature, the contacts automatically return to their original state. Open on rise contact design is typically used for refrigeration defrost termination and ice cube maker control. The type 39TR includes an internal resistor wired in parallel with the contacts which serves as an aid to factory circuit testing where the contacts are open at room temperature.

Mounting Configurations:

The 39T has been specifically designed to permit easy mounting onto copper or aluminum tubing with excellent retention and thermal response. The stainless-steel mounting bracket has been designed to accommodate a wide range of tubing sizes without the need to modify the control platform or worry about thermal response. To assure compatibility with other materials, the 39T can be provided with either an aluminum or tin-plated copper sensing surface. The rugged design of the sensing surface permits carefree handling regardless of the sensing material chosen.

Thermal Response:

The temperature sensitive bimetal disc is located at the bottom of the disc cup adjacent to the surface to be monitored. Aluminum and tin plated copper cups are available for calibrations not exceeding 221°F (105°C) and temperature overrides not exceeding 250°F (121°C).

Lead Wire and Terminal Configurations:

Standard Lead Wire – The standard leads for the 39T controls are 12” (305mm) #18 AWG, 16/30 standard copper wire with 1/32” (0.8mm) thick 105°C PVC odorless insulation stripped 1/2” (13mm). Non Standard Lead Wire – Leads longer than 12” (305mm) are available for all 39T controls at added cost. The standard lead wire can also be supplied with tracer or with 1/16” (1.6mm) insulation. In addition, #16 AWG wire can be supplied with either 1/32” (0.8mm) or 1/6” (1.6mm) thick insulation. The maximum wire size available is #14 AWG with 1/32” (0.8mm) insulation. Lead wire insulation, along with other materials in the 39T, all meet the refrigeration industry’s taste and odor tests.