Final answer:
According to the NEC, there is a general limit of 1.8 meters (6 feet) for using flexible metal conduit, but there is no set limit for trade size 12 (3/8") conduit as it can vary depending on the application and local amendments. Always consult the current NEC or a professional electrician for exact requirements.
Step-by-step explanation:
The question is concerning the electrical installation guidelines for flexible conduit. According to the National Electrical Code (NEC), particularly in Article 348, there are specified limits to the length of flexible conduit that may be used in certain situations. When flexible metal conduit (FMC) is used to connect to moving equipment or for vibration isolation, or when it is used to make difficult bends, the maximum length of FMC permitted is 1.8 meters (6 feet) unless otherwise permitted by other sections of the Code. However, when referencing trade size 12 (3/8") conduit specifically, the Code does not set a standard length and it can vary based on the application and specific local amendments to the Code.
It is important to consult the most current NEC or a qualified electrician to confirm the allowable length for your specific application, including any local code amendments that may impose additional restrictions or allow for specific exemptions.