What must be avoided according to NEC when using dissimilar metals in electrical installations?

When using dissimilar metals in electrical installations, it's crucial to avoid corrosion. The National Electrical Code (NEC) highlights this concern because different metals can react with each other through galvanic corrosion when they are in contact in the presence of an electrolyte, such as moisture. This type of corrosion can lead to the deterioration of the metal surfaces, which results in compromised electrical connections. Over time, corrosion can create increased resistance, which can lead to overheating, voltage drops, and ultimately, equipment failure or safety hazards.

Although heat generation and electrical discharge may be factors to consider when managing electrical installations, they are not directly related to the selection and use of dissimilar metals. Additionally, the size of the conductors, while important for ensuring proper current carrying capacity and preventing overheating, does not address the concerns stemming from corrosion between different metal types. Thus, the focus of the NEC on corrosion ensures the longevity and safety of electrical installations where dissimilar metals are present.