Self-Hold Thermal Protectors Prevent Contact Breakage in High Voltage Applications


Selco Products new UB8P and UB81P Self-Hold Thermal Cut-Out and Thermal Protectors are designed to provide overheat protection in high voltage applications. With a high 16 Amp capability, the new models are well suited for thermal overload protection in a broad range of applications, including space heaters, dishwashers, mixers, blenders, grinders and other electronic appliances. The body of these surface mount devices are manufactured of phenolic resin and feature a new patent pending partition wall design that isolates the switch from the main body. This design effectively controls arcing that can cause a break in voltage contact (particularly in 250V applications), ensuring continuous operation to setpoint. The UB81P features a reinforced PBT enclosure for dust-proof applications; the UB8P has an exposed bi-metallic element for high accuracy and fast response to ambient air temperature. Both models incorporate a “self-hold” non-self resetting function that provides a high level of operational safety, especially in appliances with moving parts. The “self-hold” function ensures that after the element reaches its pre-set open temperature, the internal heater activates to maintain a self-regulating temperature, preventing the switch from resetting until the user disconnects the power. Measuring 31.5 mm x 6.5 mm x 4.2 mm, the UB8P and UB81P feature an operating temperature set range from 75 to 145°C. Temperature tolerances are ± -5, ± -7, and ± -10°C with a standard differential of 30°C±15°C. Contact ratings are 16 Amps at 125V and 10 Amps at 250VAC to 6,000 cycles. The UB8P and UB81P Models are manufactured with a built-in ceramic PTC (positive temperature coefficient) self-regulating heating element, which is positioned directly next to the bimetal-sensing switch. This design provides efficient insulation and fast thermal response time compared to units where the heater is mounted externally to the thermostat. Agency approvals include a UL rating of 16 Amps at 125VAC, 6,000 cycles resistive down to 125°C and a European rating of 10 Amps (5A) at 250VAC, 6,000 cycles resistive (inductance) down to 125°C.
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