Electrical Cable Insulation Class: Complete Guide to Identify and Apply It

When it comes to the reliability and safety of electrical cables, the insulation class is a fundamental parameter.
However, this term can be confusing, because it has two main meanings:

• Electrical insulation class, related to protection against electric shock (classes 0, I, II, III).
• Thermal insulation class, instead related to the resistance of the insulating material to high temperatures.

What “thermal insulation class” means in electrical cables

The thermal insulation class is a classification defined by international standards (IEC, CEI, UL) to identify the ability of an insulating material to withstand heat over time.
Each class corresponds to a maximum temperature beyond which the material degrades or loses its insulating properties.

This classification is mainly used for:

• electric motors and transformers;
• industrial equipment;
• high-temperature electrical cables, such as those produced by Caviterm.

To learn more about how to protect a conductor from heat and choose the most suitable material, you can also read our guide on how to insulate electrical cables from heat.

Thermal insulation classes: table and maximum temperatures

Class	Maximum operating temperature (°C)	Typical insulating materials
A	105	Paper, cotton, materials impregnated with natural resins or varnishes
E	120	Polyester, synthetic resins
B	130	Mica, treated glass, epoxy resins
F	155	High-performance polyester, silicone resins
H	180	Silicone, fiberglass, mica-silicone
C	> 180	PTFE, mica, ceramic, glass, mineral materials

In Caviterm cables, operating temperatures exceed 250 °C, a value that goes beyond Class C, which is not yet formally standardized.

These cables use special insulating materials such as mica, polyimide, PTFE (Teflon), and fiberglass types “E” and “R/S”, capable of ensuring thermal stability, consistent insulation, and long service life even in extreme environments.

For more details about the techniques and materials used, see the section dedicated to electrical cable insulation.

Why thermal insulation class is important

Knowing the thermal insulation class of a cable is essential for:

• Ensuring safety and reliability: an unsuitable insulation can overheat, lose efficiency, or cause failures.
• Extending system lifespan: choosing materials with a higher thermal margin reduces aging and maintenance.
• Complying with technical standards: CEI and IEC regulations define maximum operating temperatures for each class.

For Caviterm cables, designed for ovens, heaters, sensors, and industrial machinery, the choice of insulating material is a key design factor.

High-temperature insulating materials in Caviterm cables

High-temperature Caviterm cables use insulations and jackets that maintain their properties well above 250 °C, thanks to materials such as:

• Fiberglass “E”: excellent heat and flame resistance, self-extinguishing;
• Mica: exceptional thermal and dielectric insulation, ideal for high temperatures and demanding voltages;
• PTFE (Teflon): excellent mechanical and chemical stability, resistant up to 260 °C;
• Silicone: flexible, resistant to thermal shocks and mechanical stress;
• Fiberglass “R/S”: used in extreme conditions, even up to 700 °C.

Thanks to these solutions, Caviterm cables maintain consistent performance even in environments where traditional insulating materials cannot be used.

To properly evaluate the thermal performance of a system, it may also be useful to understand electrical cable temperature calculation, in order to correctly size the installation.

How to choose a cable based on insulation class

The selection of the correct cable depends on:

1. Operating temperature of the system or environment;
2. Type of thermal and/or mechanical stress;
3. Installation conditions (in air, conduit, near heat sources, etc.);
4. Expected operating cycle duration.

For standard applications, Class F or H cables may be sufficient, but in most industrial applications, it is necessary to use higher-class cables (above 250 °C), such as those designed by Caviterm.

Conclusion

The insulation class of electrical cables is an essential parameter for ensuring safety, durability, and compliance.

In the case of Caviterm cables, the concept of insulation goes beyond traditional classifications: special materials and dedicated manufacturing processes allow operating temperatures above 250 °C, ensuring reliable performance even in the most extreme conditions.