Conductor Size - Pump Application

[rslife]

I'd like to confirm the conductor size required by NEC for a power cord on a small pump. When I determine the voltage drop for the below values, I find 2.1 volts (1.75%). This would tell me the 16/3 cord should be adequate, as long as it has the ampacity (and it should). Yet many online calculators I've used recommend 14 gage wire, even if I reduce the cord length to 5 feet. Is there an NEC requirement that drives this? Thanks.

Full load current = 4.2 amps
Cord length (pump to plug) = 50 ft
Conductor size = 16 AWG, 3C (copper)
Supply voltage = 120 VAC

 

[iwire]

310.5 says the minimum size conductor for 120 volt circuits is 14 AWG unless permitted elsewhere in the code.

I do not know a code section that allows a 120 volt motor to be supplied with less than 14 AWG.

 

[david luchini]

310.5 says the minimum size conductor for 120 volt circuits is 14 AWG unless permitted elsewhere in the code.

I do not know a code section that allows a 120 volt motor to be supplied with less than 14 AWG.

I would think that the second paragraph of 430.6 would permit a flexible cord with conductors smaller than #14 to be used on a 120v motor, as long as the ampacity is selected in accordance with 400.5

 

[iwire]

I would think that the second paragraph of 430.6 would permit a flexible cord with conductors smaller than #14 to be used on a 120v motor, as long as the ampacity is selected in accordance with 400.5

I will buy that.

 

[david luchini]

Yet many online calculators I've used recommend 14 gage wire, even if I reduce the cord length to 5 feet.

The online calculators are probably based on using "conductors for general wiring" instead of "flexible cords," and as Bob pointed out, #14 would be the smallest allowed "conductor for general wiring" per 310.5.

But your cord should be OK, with an ampacity per 400.5.

And there are no NEC requirements for voltage drop, only fine print notes, which are informational but not enforceable - except for, I think, Sensitive Electronic Equipment (Art. 647) and Fire Pumps (Art. 695), though I may be forgetting something.

 

[rslife]

Thanks for the help. I suspected there was another section in NEC that described this application, but didn't know where.

 

[Cow]

Wow.

Somebody taught Iwire something. I'll mark it on my calender....:grin:

 

[Dennis Alwon]

Wow.

Somebody taught Iwire something. I'll mark it on my calender....:grin:

Mark it but I am sure Bob knew that. He's just getting old and forgot.:grin: