While the NFPA allows the use of MTW or THHN wire inside control panels, MTW is often preferred for its flexibility and easier handling. Type TFFN (stranded) wire is primarily used as fixture wire as specified by the National Electrical Code (NEC). Type THHN wire is intended for general purpose applications. Type DLO is ideal for heavy duty wet/dry power connections requiring flexing capability.
Type MTW conductors are primarily used in control cabinets, in machine tool applications and appliance wiring applications at temperatures -25°C to 105°C. MTW wire complies with the National Electrical Code (NEC) and NFPA Standard 79. Voltage rating for all applications is 600 volts. Now available spiral striped MTW wire (NFPA Standard 79).
Type TFFN (stranded) conductors are primarily used as fixture wire as specified by the National Electrical Code (NEC), at temperatures not to exceed 90°C in dry locations. Voltage rating is 600 volts.
Type THHN building wire is intended for general purpose applications. It is appropriate for new construction or rewiring for 600 volt applications. When used as type THHN, the conductor is suitable for use in wet or dry locations at temperatures not to exceed 90°C or not to exceed 75°C in oil or coolants.