According to NFPA 70, what determines the type of insulation used on conductors in an installation?

The type of insulation used on conductors in an installation is primarily determined by the environment in which the conductors will be operating. This includes factors such as temperature, moisture, exposure to chemicals, mechanical stresses, and potential exposure to sunlight or other degrading conditions. Different environments require specific types of insulation to ensure the conductors operate safely and reliably under those conditions.

For instance, conductors used in wet locations require insulation rated for moisture resistance, while those exposed to harsh chemicals need insulation designed to withstand such exposure. This approach ensures that the installed conductors will have the necessary protection against possible damage, reducing the risk of electrical failures or hazards.