Why should millivolt wiring be isolated from line voltage wiring?

Millivolt wiring should be isolated from line voltage wiring primarily because line voltage can induce a voltage into the millivolt wiring. This is important to understand because millivolt systems are designed to operate with very low voltage levels and can be sensitive to interference from higher voltage systems. When line voltage wiring is in close proximity to millivolt wiring, the electromagnetic fields generated by the line voltage can couple with the low voltage millivolt systems and induce an unwanted voltage. This induced voltage can lead to inaccurate readings, malfunctioning of sensors, and unpredictable behavior of the devices relying on the low voltage system.

Maintaining isolation between these two types of wiring ensures that the millivolt system operates reliably and accurately without being affected by fluctuations or interference from the line voltage. Such precautions are critical in installations where both types of wiring may share the same conduits or spaces, as it protects the integrity and functionality of the millivolt systems.