A large fastened-in-place load is one that needs more than 50% of the circuit rating. That prevents you from putting lights or receptacle on the circuit. I would expect most well pumps to be in the 10 to 20 amp nameplate range at 120V or half that at 240V. But electricians tend to use the 250% rule for motors, so you end up with larger circuits than you need. Once over 20A, you can't use normal receptacles anymore. At 30A, you may only be allowed heavy duty lampholders.
The OP said a 30A circuit. The few wells I've seen had 30A circuits. Seems overkill for the typical size of a pump motor, but I haven't done any wells myself. I don't know if the OP's circuit was truely a single well pump circuit pushing the 250% breaker limit, or if a 20A circuit would work just as well plus allow regular lighting and receptacles. Depends on the size of the well pump. But I would consider a well pump to be fastened-in-place, and even a 10A pump is using up half the circuit so you can't add lights or receptacles to that circuit. A 240V pump and a 120/240V 20A multiwire circuit would probably solve the problem in many cases.
