Where I work there's two rated 30 amp receptacles and two 20 amp receptacles on one 208 VAC /20 amp breaker. I was told by senior mechanics that because the circuit's wired with 10 AWG and only one milling machine is used at any given time it's acceptable. None of the machines can draw 30 amps but some have the 30A plugs for whatever reason put there by mechanics who already retired. The code book (in my understanding) states that a 30A receptacle can only be wired to a 30A breaker. This to me means it cannot be wired to a 20A breaker. Am I missing something here? Suggestions were made to change plugs or use adaptors and remove the 30A receptacles. Or we could rewire another separate 30A circuit for the 30A receptacles or change the circuit to 30A with a 20A disconnect to the 20A receptacles. Some say leave it as is and it's not against code. Thanks in advance for any input.