Thermal protectors

The thermal switches or temperature limiter of Alpha Therm found everywhere in applications where a reliable protection against over temperature is required. When reaching the switching temperature, the bimetal snaps in temperature switches over, breaking a contact system and thereby interrupting the electrical circuit of the device to be protected. After cooling and after reaching the reset temperature, automatically reset and thus the closing of the contact system. The circuit is thus closed again.


They are frequently used in transformers, power supply units, heaters, electric motors, solenoid valves, fan, water heater, ballasts, alarm systems, electronic circuits, power transistors, and many more.

Thermal protector UK series


surface mount,

plastic case,

lead or lead wire,

50°C to 145°C

AC 250V / 2A


Thermal protector ST01 U3 series


without insulation, impregnation resistant, current insensitive,

NC or NO

60°C to 180°C

AC 250V / 5,0A


Thermal protector ST01 U4 series


with epoxy cover, impregnation resistant, current insensitive,

NC or NO

60°C to 150°C

AC 250V / 5,0A


Thermal protector ST01 U5 Serie


Transparent shrink cap insulation, impregnation resistant, current insensitive,

NC or NO

60°C to 180°C

AC 250V / 5,0A


Thermal protector ST-22 series


surface mount,

plastic case,

lead or lead wire,

50°C to 145°C

AC 250V / 7A


Thermal protector ST01 U2 series


without insulation, impregnation resistant, current insensitive,

NC or NO

60°C to 180°C

AC 250V / 5,0A


Thermal protector ST01 U6 series


plastic case for screw-on, impregnation resistant, current insensitive,

NC or NO

60°C to 180°C

AC 250V / 5,0A


Thermal protector ST01 U8 series


plastic case for screw-on, impregnation resistant, current insensitive,

NC or NO

60°C to 180°C

AC 250V / 5,0A


Thermoschalter UK Serie Thermoschalter ST22 Serie

Thermal protector B12 series


surface mount,

NC or NO

70°C to 190°C

AC 250V / 10A (max. 30A)


Thermal protector ST12 series


screw on,

60°C to 150°C

AC 250V / 13A (max. 30A)


Disc thermostats AT-T23 series


screw-in or screw-on mounting,

AC 250V / 16A

50°C to 175°C


Thermal protector Q series


surface mount,

plastic case,

with electrical self-hold,

wire or lead wire,

40°C to 150°C

AC 250V / 2,5A


Disc thermostats TK24HT series


screw-in or screw-on mounting,

AC 250V / 10A

250°C to 425°C


Disc thermostats TK24 series


screw-in or screw-on mounting,

AC 250V / 10A

-45°C to 250°C


Mounting bracket


Mounting brackets for thermal protectors


Thermoschalter Q Serie Thermoschalter TK24HT Serie Thermoschalter B12

Thermal protector ST01 U9 series


plastic case,

impregnation resistant, current insensitive,

NC or NO

60°C to 180°C

AC 250V / 5,0A


Thermal protector ST01 U1 series


shrink cap insulation, impregnation resistant, current insensitive,

NC or NO

60°C to 180°C

AC 250V / 5,0A


Thermoschalter Q Serie Thermoschalter Q Serie Thermoschalter Q Serie Thermoschalter Q Serie Thermoschalter Q Serie Thermoschalter Q Serie Thermoschalter Q Serie Thermoschalter Q Serie Thermoschalter Q Serie

Thermal protector ST01 U7 Serie


with M4x6mm thread for screw-in mounting, imprägnierbeständig, current insensitive,

NC or NO

60°C to 180°C

AC 250V / 5,0A



α Therm


Alpha Therm GmbH - Your specialist for temperature-limiting

safety components, sensor elements or sensors

© 2017 Alpha Therm GmbH

v 2.4

Home Products Contact About us Shop Imprint

Phone: +49 6202 / 575688 - 0

Temperature protection

Temperature Protection

Temperature sensors

Temperature sensors

Overload protection

Overload protection

Surge protection

Surge protection

Temperature sensor elements

Temperature sensor elements

Temperature controller

Temperature controller

Mechanical switches

Mechanical switches

Online shop

Download product overview