Question on voltage drop

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daryl

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I have a buddy who needs a 20 amp GFCI about 300 feet outside from his house to power A pond waterfall and low volt lights. He needs all 20 amps. Actually only about 14 but the start up amps for the pump are like 20 amps. Anyway I heard that every 100 feet we should up the wire size, to accomodate voltage drop. I can't find it in the code book. Do I have to run #6 wire out there. Please help Thank You
 
Re: Question on voltage drop

Using 20 amps, #6 at 300 ft will give you (rounded up) 115 volts, so I'd say yes you need at a minimum #6.

Roger

[ April 20, 2005, 08:48 PM: Message edited by: roger ]
 
Re: Question on voltage drop

so bring the #6 through the pvc, into the box, and then wire nut #10 to it to put into the back of my GFCI? I know it would work but sounds weird, and would look weird what do u think?

[ April 20, 2005, 08:56 PM: Message edited by: daryl ]
 
Re: Question on voltage drop

Daryl, I'd reduce to a #12 in the device box (oversized box if possible) and the panel.

Roger
 
Re: Question on voltage drop

Sorry if I sound stupid but I should wire nut it in the panel too huh? #6 won't fit in a 20 amp breaker? I've actually never tried it, so I don't know if it would or not. I believe I have to up my ground to don't I?
 
Re: Question on voltage drop

Daryl, yes you will most likely need to wire nut a #12 to the #6 in the panel to fit into the breaker.

You are correct that you will need to increase your EGC proportionately, see 250.122(B) 2002 NEC.

Roger
 
Re: Question on voltage drop

If the motor draws 14 amps at 115 volts, and it can be connected for 230 volts, the current will decrease to 7 amps. The single-phase voltge drop for 14A @ 120V is 3.4 percent or 4.125 Volts for NO. 6 copper conductors. For 7A @ 230V, No. 10 copper will give a VD of 2.25 percent or 5.2 Volts.
 
Re: Question on voltage drop

hi i get a different number
i am assuming single phase, 115v, copper wire
i use vd=2xkxIxd/cm
d/cm=300/52620cm (#3) =.00570
k=12.9 for copper
I=20amps load
vd=2x12.9x20x.00570 and i get 2.94 percent
that is under 3 percent so number 3's
 
Re: Question on voltage drop

Guys, If I'm reading this correct he said it was 300 feet away. Remember that you must add the return also on this distance. So 300' x 2= 600' we need to figure for voltage drop.#4 uncoated copper at this distance would give you a 3.7 voltage drop if I did my math correct for a 20 amp load. A #6 at this distance at a 14 amp load would be a 4.124 voltage drop. I believe I did my math right.
Jim
 
Re: Question on voltage drop

I just checked Roger's first post (out of curiousity) and it's accurate.

I may have converted it to different terms, but it's still correct.

I hav'nt looked at any other posts.
 
Re: Question on voltage drop

I will store it next to zinsco and fed pacifics.To me they are about the same.Do others find they change out far more GE than square d or other top brands ?
 
Re: Question on voltage drop

Jim, are you posting in the right thread? :roll:

Roger
 
Re: Question on voltage drop

Hello Sam, of course my post was accurate. :D

Roger
 
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