Nameplate OCPD max

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ParagonBuilder

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Is there a code that states that we must follow nameplate data. I wired a 2-1/2 ton furnace yesterday, and my boss wanted to know why I didn't run 12 gauge. He says, "We always run 20 amp circuits for dedicated runs, and besides motors require a min of 20 circuits per NEC."
I showed him the nameplate which was 11 amp minimum ampacity and 15 amp maximum over current device.
He said manufacturers cannot overrule the NEC.
He is supposed to show me this 20amp motor rule...
I find nothing other than the standard 125 percent calcs.
As far as I understand it, if he wants to run 20 amps to the furnace it would need an ssu or equivalent.
Am I off base here?
 
There is no code that requires a minimum of 20 amps. Your boss is off base with that but if he wants a 20 amp circuit then that is what you should run. If you run a 20 amp circuit you would need a fused disconnect to fuse it down to 15 amps or you could just use an unfused disconnect and install a 15 amp breaker on the 12 gauge wire
 
Dennis Alwon said:
There is no code that requires a minimum of 20 amps. Your boss is off base with that but if he wants a 20 amp circuit then that is what you should run. If you run a 20 amp circuit you would need a fused disconnect to fuse it down to 15 amps or you could just use an unfused disconnect and install a 15 amp breaker on the 12 gauge wire
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Ok thanks. That's how I understand it. Does the code state that the maximum over current device must meet the nameplate specs. Ive always just done that, but can't find it actually written in the NEC.
 
ParagonBuilder said:
Ok thanks. That's how I understand it. Does the code state that the maximum over current device must meet the nameplate specs. Ive always just done that, but can't find it actually written in the NEC.
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Here is the section

110.3(B) Installation and Use. Listed or labeled equipment
shall be installed and used in accordance with any instructions
included in the listing or labeling.
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ParagonBuilder said:
Ok thanks. That's how I understand it. Does the code state that the maximum over current device must meet the nameplate specs. Ive always just done that, but can't find it actually written in the NEC.
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No, if the MCA were say 18 amps and the maximum OCPD size is 25 amp you could use a 20 amp OCPD. The MCA is just that the minimum circuit ampacity. You are correct you must follow the nameplate.
 
infinity said:
No, if the MCA were say 18 amps and the maximum OCPD size is 25 amp you could use a 20 amp OCPD. The MCA is just that the minimum circuit ampacity. You are correct you must follow the nameplate.
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Right thanks, I knew you could go smaller, but my boss wants to use a 20 amp circuit with no additional fusing. So this is clearly wrong in this case.
I will spar with him on this Monday morning. I just wanted to be sure before I pushed.
 
ParagonBuilder said:
Right thanks, I knew you could go smaller, but my boss wants to use a 20 amp circuit with no additional fusing. So this is clearly wrong in this case.
I will spar with him on this Monday morning. I just wanted to be sure before I pushed.
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Hey it's his money so if he wants you run larger conductors that's fine but you would still need an OCPD no larger than 15 amps.
 
14 AWG is smallest conductor you can use as a general rule, with some special cases where you can go even smaller - but usually limited to control wiring. Makes no sense to me in some instances to run 12 AWG when 14 AWG is more then enough to handle the load - say a 1/2 hp 480 volt motor that only has a NEC stated FLA of 1.1 amps. You can even put that on a very long 14 AWG run and still not even have a voltage drop issue.
 
ParagonBuilder said:
That was what i told him yesterday and he through the 20 amp min on a motor at me. He said he would show me in the code. I'll be waiting...
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You may be waiting a long time...

More likely is that he worked somewhere that had an INTERNAL standard of a 20A circuit for all motor loads. When I worked at a steel mill, that was our standard. All single pole breakers (other than in the office areas) were 20A minimum run with 12ga wire. If a machine had an MOP rating of 15A, it still got a 20A circuit in the panelboard, then a 15A fuse at the local disconnect for it.
 
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