What is the maximum ampacity of #12 rated wires THWN?

The maximum ampacity of #12 gauge THWN wire is indeed 20 amps. Ampacity refers to the maximum amount of electrical current a conductor or device can carry before sustaining immediate damage or heating excessively.

In the case of THWN (Thermoplastic Heat and Water resistant Nylon-coated) wire, which is commonly used in residential and commercial electrical systems, it has a specified ampacity based on its gauge, which corresponds to the size of the wire. According to the National Electrical Code (NEC) guidelines, #12 gauge wire is typically rated for up to 20 amps in standard residential applications, provided it is appropriately installed and protected.

This rating assumes a standard operating condition and might vary under different circumstances, such as the type of insulation, ambient temperature, and installation conditions. However, for general purposes and under typical conditions, the established maximum ampacity for #12 THWN wire is confirmed to be 20 amps, making it suitable for a range of common electrical tasks.