The primary difference between Class F and Class H insulation is their maximum permissible operating temperature. Class H is designed for extreme duty, offering higher thermal endurance and better resistance to heat compared to Class F.
Neither insulation class is universally "better"; it depends on your operating environment.
Class F insulation is rated to withstand temperatures up to 155°C. This means the motor's winding insulation can handle higher thermal stress compared to lower classes, which makes it ideal for running in demanding environments.
With modern designs, a 'Class B' temperature rise is readily achievable. Therefore Class F insulation with a Class B temperature rise gives us a thermal margin of 25°C, potentially increasing the life of the motor by up to 5 times.
Class H insulation consists of materials such as silicone elastomer and combinations of materials such as mica, glass fibre, asbestos etc., with suitable bonding, impregnating or coating substances such as appropriate silicone resins.
- Class F • Suitable for many standard industrial applications • Limited thermal margin under continuous heat • More sensitive to repeated thermal cycling - Class H • Designed for severe operating environments • Higher thermal endurance • Better resistance to heat, load variations, and long duty cycles In applications ...
Typical recommendations for exterior walls are R-13 to R-23, while R-30, R-38 and R-49 are common for ceilings and attic spaces.
Four primary types of electrical insulators used in overhead power lines are pin insulators (low-to-medium voltage), suspension insulators (high voltage), strain insulators (high tension/sharp turns), and shackle insulators (low voltage distribution). These materials prevent current leakage by separating conductors from structures.
Class H: Insulation systems in Class H need to tolerate temperatures up to 180°C, with a minimum wire temperature rating of 150°C. Class R: Class R insulation systems are designed for extreme conditions, requiring a minimum insulation temperature of 220°C.
F-factors for concrete slabs-on-grade are determined via computer analyzes and depend on such design variables as soil thermal conductivity, soil thermal mass, insulation thermal resistance, insulation location, whether the slab is heated or unheated, slab position with respect to grade, location of the ground water ...
Class F is encapsulated Nylon coil. Class H is encapsulated Phenolic coil (types H1 and H2 are open wound (not encapsulated)).
The main difference is that the class designations refer to the withstand temperature of the insulation material in Tricast cast resin dry type transformers. Thus, H class has a wihstand temperature level of 180 ⁰C for the coils and F class of 155 ⁰C for ambient design temperature of 40 ⁰C.
In terms of temperature, a 200g insulated winter boot will keep your feet warm down to about 0-10 degrees (F), while a 400g winter boot will keep them warm down to -20 degrees (F) and possibly lower. Generally speaking, you can wear a pair of 200g winter boots in 20-30 degree Fahrenheit temperatures quite comfortably.
Key features and benefits
Ceramic fiber products are not only versatile, but they also offer significant cost savings. They are offered for various oil and gas applications at temperatures up to 2800°F (1540°C).
5 Most Common Thermal Insulation Materials
There are five categories of insulation used by the different classes of equipment; functional, basic, supplementary, double and reinforced: Functional insulation - basic level that is required for the supply to function. This does not prevent electric shock if touched.
Three effective insulators that restrict the flow of heat or electricity are rubber, glass, and plastic. These materials are widely used because they have high resistance to electron flow and poor thermal conductivity.
Closed cell spray foam is rigid once set. It is a better thermal insulator and was previously sold to stabilise failing roofs. But if it has been used inappropriately or installed poorly, it might put stress on timbers, restrict air circulation and put them at risk of decaying.
The "best" home insulation material depends on your budget, project type, and goals. There is no single universal choice, but rather four standout materials that dominate modern construction.
The Environmental Protection Agency banned spray-on asbestos insulation in 1973, certain types of pipe and block insulation in 1975 and new asbestos insulation products in 1989. In 2024, the EPA banned most uses of chrysotile asbestos products, including imports.
Fiberglass is the most common type of insulation, making up over half of all residential installations. Made of finely woven glass fibers, it is highly cost-effective, easy to install, and readily available.
Injection Foam. USA Premium Injection Foam® Insulation is a proprietary product we manufacture in-house and used only by our trained technicians. This product can be used on both exterior and interior walls where it is injected into a close wall cavity (eg: a finished wall).