Feedback on voltage drop situation

[sw_ross]

I'd like some feedback on an install I'm working on.

I'm running a 120v circuit out to a 4/10 hp lift pump in a septic tank. It's about 240-250 feet from the panel to the tank. I did a voltage drop calc. and came up with about 8 volts of drop, or 6.7% (FLC from NEC 430 charts).

When I brought this up to my boss and asked if he wants to up the wire size, he acted surprised that I was concerned about the issue. He has more experience with this sort of thing than I do. I know what the books say, but in real world situations am I overly concerned about this?

Thanks,
Sky

 

[mcclary's electrical]

What size wire did you use for a calculation? We're only talking about 311 watts. 311 watts is a small load. Unless you're using speaker wire, you should be fine:grin:

 

[ceb58]

Assuming a voltage of 120 and a 3amp load you can run 293ft with #12 and have only a 3% vd.

 

[Jim W in Tampa]

Should be ok. Would rather see it in #10 but your boss makes that call as its his money. You did the right thing and called it to his attention.

 

[sw_ross]

Wouldn't a 4/10 hp motor at 120v be around 8 amps FLC? (from 430.248)

P.S.- Thanks for the feedbacks so far!
Sky

 

[weressl]

Wouldn't a 4/10 hp motor at 120v be around 8 amps FLC? (from 430.248)

P.S.- Thanks for the feedbacks so far!
Sky

Use the nameplate data for VD calculations.

 

[winnie]

IMHO for this application, the key voltage drop issue won't while the motor is running, but instead the voltage drop while the motor is starting.

-Jon