Motors conductors voltage drop why me?

[ray456]

This three phase motor is fed with two #4 al and one #6 al (yup SER cable). I did the calculations and the # 4 is on the edge of being okay. The #6 is over 4% drop.

I quoted a price to run a new #6 copper feed, also a shorter run than the old SER. The customer then asked if we could use the feed to an existing panel (two #2 al and one # 4, more SER) to feed the motor. The panel does not have much in it so using the #4 SER would be okay.

So, the million dollar questions...

Is it a violation to run different size conductors to a three phase motor?

Will doing this hurt the motor?

How do I always find these jobs? (haha)

Any help or wise a$$ remarks welcome!

Ray

 

[bphgravity]

Re: Motors conductors voltage drop why me?

Where is the equipment grounding conductor? Metallic raceway?

I do not believe there is anything in the code that prohibits different sized ungrounded conductors used in one circuit. As long as the smaller conductors are sized properly, there should not be a problem. The larger conductors will simply operate cooler.

 

[charlie]

Re: Motors conductors voltage drop why me?

Bryan, you are correct. However, a motor can only handle so much voltage imbalance. I doubt that there would be enough on a run to make much difference but it is possible.

 

[ray456]

Re: Motors conductors voltage drop why me?

Where is the equipment grounding conductor? Metallic raceway?

SER cable has two black conductors one white conductor and an uninslated equipment ground.