However, engineering practice says motors should operate at temperatures much less than this. Motors must now meet the new NEMA operating efficiency standard. Efficiently operating motors reduce energy consumption costs as well as help increase motor life. Larger conduit box. The 1994 specification calls for a conduit box that is at least twice the size of the NEMA standard box.
Many manufacturers already comply, as a part of good engineering practice.
The increase in size ensures enough room for termination of cabling. Low vibration in conjunction with a good installation, alignment, and base design provides a smooth operating system, as well as helps prevent premature bearing failure from mechanical stress. This limit does not apply to roller bearings. Motor manufacturers will test vibration at no load on an elastic mounting, or when the motor is bolted to a heavy, flat base. Manufacturers must add a ground connection point on the motor frame, external to the terminal box.