Fit and mounting — what to check before you swap
The G12E4F50: Fixed mount on a backplate (not DIN rail). 100 mm wide, 130 mm tall, 60 mm deep — that's a compact footprint for a 4-pole 50 A MCCB. Screw terminals up top and down below, both front-accessed, so you can land cables without reaching around the back. Connection pitch is 25 mm, standard for this class. Neutral is on the left when viewed from the front. IP20 finger-safe terminals, fine for enclosed panels; not for washdown.
The TM-D trip unit gives you LI protection: thermal overload (L) and magnetic short-circuit (I). The thermal element tracks heating in the conductor, so you can size it for a feeder or a moderate motor load — but this is a distribution breaker (Category A), not a motor-protective device with adjustable overload curves. The magnetic trip is fixed, not adjustable. 8000 electrical cycles at 415 V at full rated current; 30000 mechanical cycles. That's service life for a panel feeder that sees a few operations a year, not a switching-duty contactor.