NEMA motor frame

NEMA motor frame codes are standardized dimensional designations published in NEMA MG 1. The frame number fixes the bolt pattern, shaft height (D dimension), shaft diameter, keyway, and mounting features. Two motors with the same frame number from any compliant manufacturer are mechanically interchangeable.

What it is

A “215T” motor has a 5-3/8 inch shaft height (the “21” times 1/4 inch), the T-frame shaft diameter (1-3/8 inch for 215T), and the T-frame mounting pattern. Larger numbers mean larger frames. A trailing “TS” denotes a short shaft for direct drive applications, distinct from “T” which is the long-shaft / belt-drive variant. “U” frames predate “T” frames and are encountered in equipment from before the 1960s frame size revision.

Why it matters

When a compressor motor fails, the replacement must match frame and mounting type. A right-frame-but-wrong-type replacement (e.g., TS instead of T) will not bolt up to a belt-driven compressor. Service techs reading the failed motor’s nameplate go first to the frame designation, then to the HP, speed, voltage, and bearing arrangement.

How it is used in our catalog

Motor frame size is reported in the spec table of each compressor entry where the manufacturer publishes it. For motor-only replacements, contact a listed installer who can verify NEMA frame compatibility against your existing mount.

Common questions

What is the difference between T-frame and IEC frame?

T-frame is the North American NEMA standard. IEC frame (used in Europe and most of the rest of the world) uses a different numbering system (e.g., IEC 100L, IEC 132M). Cross-references exist but are not exact; mounting adapters are sometimes required.

How do I find the frame on my existing motor?

The motor nameplate lists FRAME or FR. If the nameplate is illegible, measure shaft height and use a NEMA MG 1 cross-reference table.