Question about equipment power cords

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Aleman

Aleman

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Southern Ca, USA
Does the NEC specify regarding power cords for machinery that plug into a receptacle? What brought this up is a compressor being put back into service. It draws about 15 amps at 208V 3P. The plug on the compressor was a 30 amp and the wire was 14-4 SO cable. So even though the 14 awg wire is ok for 15 amps, it can be plugged into a 30amp circuit. So, should the wire be sized according to the supply or the load? I would think if the load has over current protection it would be ok, otherwise the wire would need to be sized for the supply.

I looked and couldn't find an answer. But it is possible I am being blind. My wife tells me that all the time.
 
Read 406.8 non interchangeability. Also check table 210.24 Summary of branch-Circuit requirement
 
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guschash said:
Read 406.8 non interchangeability. Also check table 210.24 Summary of branch-Circuit requirement
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Thanks for the pointers. The 406.8 appears to make the case that using 14awg for the power cord is ok; it doesn't specify that the wire has a certain ampacity, only that the plugs and receptacles cannot be mismatched. And that the 'device' should not be able to connect to a circuit with current or voltage that it wasn't intended for. In this case the compressor doesn't specify an amperage requirement other than what the motor uses.


The 210.24 chart shows that a 14awg tap on a 30amp circuit is ok. I looked in the definitions to see 'tap' but it's not there. Is a tap the wiring that the load uses to connect to a branch circuit?
 
jusme123 said:
Is the cord part of a UL listed piece of equipment (cord comes attached to equipment)?
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No UL listing, it just has a power box with a contactor and an overload switch. Right now it has an SO cord and plug. When it gets to where we will use it I will pipe it in. It also has a cool sticker on it...Assembled in America by Americans. Haven't seen that one before.
 
Minor point in real-ville, and with a load of "about 15 amps" one can't be too difinitive, but if it is a 15 amp motor load, and type SO cord, it would be undersized.
 
augie47 said:
Minor point in real-ville, and with a load of "about 15 amps" one can't be too difinitive, but if it is a 15 amp motor load, and type SO cord, it would be undersized.
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Hi Augie,

I am looking at the chart under 400.5 and I interpret it to read that 14awg is ok for 15 amps. This is a 4 wire circuit, 3 phases and 1 ground. Let me know where I am going wrong please.

In any case, for testing of this compressor I used 12-4 to hook it up. It did have 14-4 on it but the cord was short and I didn't think it was right. It's a 5hp motor running on 208V 3P, about 15 amps. Can't be exact, it's at work and I'm off till next wed.
 
NEC (430.6) says "use Tables" 5 HP 208 16.7 FLA X 1.25 = 21 400.5(A) #10
just sayin.......:)
 
Aleman said:
Ok, thanks for clearing that up for me. So, if I were to add a circuit for a motor of this size it would need to be 30 amp and wired with #10.
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Normally, You would select your conductor based on 430.22 and your Short-Circuit protection on 430.52
In the case of a 5 HP 208v 3 phase motor, your conductor would need a minimum ampacity of 21 amps and your SCGF protection could be a maximum of 45 amps (as always there are exceptions so look at those Articles)
 
augie47 said:
Normally, You would select your conductor based on 430.22 and your Short-Circuit protection on 430.52
In the case of a 5 HP 208v 3 phase motor, your conductor would need a minimum ampacity of 21 amps and your SCGF protection could be a maximum of 45 amps (as always there are exceptions so look at those Articles)
Click to expand...

I have to start putting sticky notes in my copy so I can find this info when I need it. You guys here really know your way around the NEC.
 
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