High-Temperature Ceramic Fiber Thermocouple Wire

Series 350 and 355
Zesta Thermocouple Wire Series 350
Zesta Thermocouple Wire Series 350
The SERIES 350 uses the ultimate high-temperature flexible insulating system. The ceramic fiber yarn’s upper temperature limit often exceeds the melting point of the material it insulates.

When an application requires flexible insulation, while pushing Type K or Type N to extreme limits, ceramic fiber insulation is the only choice.

Watlow supplies standard SERIES 350 without color coding or impregnations to minimize contaminating the pure ceramic fiber yarn. Because this insulation has no binders or impregnations, it may “flower” when stripped. Laboratory testing indicates impregnation can decrease the upper use temperature by as much as 1000°F (540°C).

The SERIES 355 construction is a cost-effective, medium insulation build of the popular SERIES 350 heavy-duty construction.
If application temperatures exceed SERIES 350 construction, specify XACTPAK® mineral-insulated, metal-sheathed cable.

Watlow: Your Heat Solutions Resource Brochure (EN)
Watlow: Vos Solutions de Chauffage Brochure (FR)
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Product Features

Performance Capabilities
  • Continuous temperature rating: 1205°C (2200°F)
  • Ceramic fiber braided yarn insulation
  • Available with an optional metallic overbraid for additional abrasion resistance


Ceramic fiber braided yarn
Continuous use temperature:
2200°F (1205°C)
Single use temperature:
2600°F (1430°C)
Resistance properties:
  • Moisture: Fair
  • Chemical: Good
  • Abrasion: Good


  • Heat treating
  • Oven and furnace survey
  • Load thermocouple