How to tell if a motor is overloaded?

Tell if a motor is overloaded by measuring its running current with a clamp meter and comparing it to the nameplate FLA. Sustained current above nameplate is the definition of overload.

The supporting symptoms: a case too hot to hold a hand on, overload relays or breakers tripping after minutes rather than instantly, sluggish starts, a burnt-varnish smell, and hum under load.

The cause is almost always the driven load, not the motor: a dragging bearing, an overtightened belt, a pump pushing more than designed, or low voltage forcing current up to deliver the same power.

A motor should not live at exactly its FLA all day; that is its ceiling, not its cruise.

Compare your clamp reading against spec with the max motor amperage calculator.