I just had my 24x24 garage built last month. The electrician who installed everything installed a 10-30r in my garage for my 60gallon air compressor. He then hooked up a 10-30p to to the compressor so I could plug it in. After doing some more research, I don't think he used the right NEMA type plug and receptacle. The compressor has 2 hot leads and a ground. The 10-30 is meant for 2 hot and a neutral. Is this even legal to use 10-30 on a new construction, or does that only pertain to stoves and dryers? Shouldn't he have used the 6-30 which is meant for 2 hots and a ground? It still works but I'm thinking he must of hooked the ground wire to neutral. The inspector just opened the breaker panel, looked around and said all good.