Asahi US-118 Hermetic Thermostats

Asahi US-118 hermetically-sealed thermostats offer the ultimate in moisture-resistant temperature control.  Unlike other epoxy-sealed disc thermostats, the US-118s are true hermetic products with a glass-to-metal seal around the terminal posts.  This ensures complete protection against moisture ingress in those high-specification applications which demand it.

The US-118 is available with both normally-open (break-on-rise) and normally-closed (make-on-rise) contacts, so they can be used to control temperature as well as switch on alarms or fan control circuits.  Temperature tolerances down to ±3K and typical differentials of 15K means close energy-efficient control – special tolerances and differentials available for volume applications.

Various mounting flanges offer both surface and through-hole temperature monitoring and several terminal options are also available.  Gold-plated contacts are a further option for very low-voltage circuits where minimum contact impedance is essential.


  • Vacuum impregnation applications
  • Gas pilot-light circuits
  • Marine heater applications


  • Hermetically sealed disc thermostats
  • Temperature set-points; From 0°C to 250°C
  • Contact ratings; 3A/125VAC (1A/24VDC)
Asahi Keiki US-118 Hermetically sealed 1/2 Asahi US 118 Hermetic Thermostat Dimensional Drawing