Silveradosparky
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- Calif.
Hello, we have several portable pumps (20 hp, 460 volt, 27FLA, with VFD on cart) that will be plugged into 60 amp receptacles. What is the proper cord sizing and where do I find it in the NEC. Thanks,
Cord size for portable equipment
- Thread starter Silveradosparky
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- New Jersey
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- Journeyman Electrician
Flexible cord requirements can be found in Article 400.
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Welcome to the Forum.
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- San Francisco Bay Area, CA, USA
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- Electrical Engineer
VFD max input amps x 1.25, adjusted for length because of possible voltage drop, rounded to the nearest legal limit on portable cord, but only if the CB/Fused Disconnect feeding it is sized that way. If the CB/FD is 60A, you use 60A cord..
So as an example, looking at an A-B 20HP 480V VFD suitable for a 27A FLC motor, no more than 3% voltage drop;
Max. Input Amps is 24.8A, x 1.25 = 31A, you are looking at #8 SO cord, assuming less than an 80ft run and a CB rated 35 or 40A max.
But if the CB / FD feeding that receptacle is 60A, the cord must be rated for 60A, so that would be #4 SO under the same circumstances.
So as an example, looking at an A-B 20HP 480V VFD suitable for a 27A FLC motor, no more than 3% voltage drop;
Max. Input Amps is 24.8A, x 1.25 = 31A, you are looking at #8 SO cord, assuming less than an 80ft run and a CB rated 35 or 40A max.
But if the CB / FD feeding that receptacle is 60A, the cord must be rated for 60A, so that would be #4 SO under the same circumstances.
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