I am looking at a plan for an auto parts store, it calls for lighting to be 20A ckts and gen outlets to be 15A, along with exhaust fans, printer ckt. Isn't there a code requiring all commercial lighting and plugs ckts to be 20 Amps? Or is that just how I've always done it?
Thanks guys,
H20

H2O:
There are no NEC requirements for 'general purpose' comm receptacles, spacing or ampacity.

However, you may have something in your local codes. Otherwise this is a design issue.

Now, talking about what I call "normal trade practices" comm work would be all #12 & 20 amp circuits; that's how I did it, but that's not NEC for GP circuits.

I would add to what John has said that using 15a. circuits for receptacles you will be looking at no more than 10 receptacles on a circuit (assume non-continuous), continuous load would only allow 8 receptacles on a 15a. circuit.

With my AHJ...

#12 is the smallest conductor permitted in Commercial Construction -- to include Romex -- and to include motor loads.

With such a local rule -- no commercial design uses 15 Amp breakers normally. No cost savings are to be had -- instead you end up using more breakers and circuits to handle the total load.