Insulation components are grouped into several classes according to NEMA classifications. They are primarily distinguishable by maximum temperature ratings. Two common insulation classes are Class N and Class F. Class N has a maximum temperature rating of 392ºF. Class F insulation has a maximum temperature rating of 311ºF. NEMA performance ratings assume an ambient temperature of 40ºC. However, the ambient temperature used in an actual application may be slightly lower or higher. The actual rating affects the degree of temperature rise that an insulation system may experience without exceeding the tolerance limitations of its prescribed class.