# 120 v 30 amp boat lift?



## RGH (Sep 12, 2011)

10/3...30amps @120'......?:no:


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## 360max (Jun 10, 2011)

NM is not suitable for wet locations


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## Mdelectrician (Nov 16, 2011)

10/3 uf


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## CopperSlave (Feb 9, 2012)

Get a small 3R disconnect, like a spa panel, and install a 2-pole 30A GFI breaker in it. Put it in line between the sub-panel and the lift...within line of sight to the lift.


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## RGH (Sep 12, 2011)

Again post #2....120'..now how FAR is the motor from the panel supplying it?....you may have a voltage drop issue here....#10 @120' ?....did you do voltage drop calc?...I would of derated the wire...:thumbsup:


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## Mdelectrician (Nov 16, 2011)

It's only 120 ft from sub panel to motor. Not far enough where I have to de-rate the wire. I'm thinking I'm just going to mount a box next to motor with 30amp single outlet and run the cord from motor right into it. That way it has disconecting means and put a 30 amp 120 v gfi breaker.


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## FastFokker (Sep 18, 2012)

Mdelectrician said:


> It's only 120 ft from sub panel to motor. Not far enough where I have to de-rate the wire.


 Love to see your calculation on that. 

You better go 220V at 20A and break the law and use the bare ground/bond. Even that reduced current is still high.. but hopefully the motor will not run for very long each time it gets used!


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## Mdelectrician (Nov 16, 2011)

Okay after thinking this through you guys are right an I need a larger wire. #8 and will change it over to 240. Do they make a 8/3 uf with an insulated ground? trying to get around running pipe. Also would a 20 amp 240v switch be sufficient for disconecting by the motor?


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## FastFokker (Sep 18, 2012)

I can't believe nobody has said to Call an Electrician, yet. lol 

The guys are usually so quick with that one.


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## Bugz11B (May 12, 2013)

Mdelectrician said:


> It's only 120 ft from sub panel to motor. Not far enough where I have to de-rate the wire. I'm thinking I'm just going to mount a box next to motor with 30amp single outlet and run the cord from motor right into it. That way it has disconecting means and put a 30 amp 120 v gfi breaker.


loss of 8.9 volts... 8.9/120*100=7.41% VD.. I would take RGH's advise 
**EDIT** Didnt read full thread I see now you already rethought it my bad. however you may be able to go with the #10 @ 240 volts, the code recommends not greater then 3% VD, however check the voltage rating of the equipment alot of stuff is rated for 110/220 or 115/230 and if your source voltage is actually 120/240 you should end up with a fine voltage at the equipment 
**EDIT #2** If it were my parents house I would stop by home depot and grab a laborer standing outside and offer him some cash to dig the pipe in for me and say "F" the UF.
**EDIT #3** Why are you trying to get away from running pipe?? you planning on cheating the depth??


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## erics37 (May 7, 2009)

Why can't you run it at 240 volts? I can't think of a scenario where not running something at the highest possible voltage isn't advantageous.


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## sbrn33 (Mar 15, 2007)

Boat lift warranties love to use voltage drop as their reason to not honor a claim. they even have their own VD calculations in the owners manual. Live by them otherwise the owner will say " hey why didn't you run the right size wire" now they won't honor my warranty and you will be the bad guy.


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## Speedy Petey (Jan 10, 2007)

Mdelectrician said:


> The red conductor i used as the ground b/c code states in MD the ground cant be bare.





Mdelectrician said:


> trying to get around running pipe.


You can't be serious. :blink: 

After reading all the posts in this thread, I'll be the first: Are you really an electrician?


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## Speedy Petey (Jan 10, 2007)

Mdelectrician said:


> Okay after thinking this through you guys are right an I need a larger wire. #8 and will change it over to 240.


If you go to 240V I bet you can stay with the #10. 

Are you aware that VD is 1/4 as severe @ 240V than it is @ 120V?


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## sbrn33 (Mar 15, 2007)

erics37 said:


> Why can't you run it at 240 volts? I can't think of a scenario where not running something at the highest possible voltage isn't advantageous.


Is running a motor at a higher voltage better for the motor? Is it more efficient?


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## FastFokker (Sep 18, 2012)

sbrn33 said:


> Is running a motor at a higher voltage better for the motor? Is it more efficient?


Rhetorical question, I'm guessing.. you must know. lol

I don't actually know, but wouldn't 240V and a lower current going through the windings make a motor last longer?


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## sbrn33 (Mar 15, 2007)

FastFokker said:


> Rhetorical question, I'm guessing.. you must know. lol
> 
> I don't actually know, but wouldn't 240V and a lower current going through the windings make a motor last longer?


The current through the windings would be the same. The voltage drop is a whole different thing.


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## Bugz11B (May 12, 2013)

Speedy Petey said:


> If you go to 240V I bet you can stay with the #10.
> 
> Are you aware that VD is 1/4 as severe @ 240V than it is @ 120V?


1/4??? 

1/2.... or am i missing something??


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## Speedy Petey (Jan 10, 2007)

Erik.Schaeffer said:


> 1/4???
> 
> 1/2.... or am i missing something??


1/4. Do the math. :thumbsup:


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## Bugz11B (May 12, 2013)

Speedy Petey said:


> 1/4. Do the math. :thumbsup:


I did the math... I understand your doing it based off of the 30A @ 120V and 20A @ 240V, but i think thats just the over current device they recommend not the running current, that should 1/2 no??

2*12.9*120*30/10380=8.94
2*12.9*120*15/10380=4.47


**EDIT** Dont take my tone as an arguing one its not i assure you (i get mistakin for arguing alot when im not, its just how I learn/understand, by having a debate like convo)


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## 8V71 (Dec 23, 2011)

1/4 percentage wise I believe.


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## hardworkingstiff (Jan 22, 2007)

Erik.Schaeffer said:


> I did the math... I understand your doing it based off of the 30A @ 120V and 20A @ 240V, but i think thats just the over current device they recommend not the running current, that should 1/2 no??
> 
> 2*12.9*120*30/10380=8.94
> 2*12.9*120*15/10380=4.47
> ...


8.94/120(volts)= 7.45% VD
4.47/240(volts)= 1.8625% VD

7.45/1.8625= 4

or

1.8625/7.45= 1/4


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## Bugz11B (May 12, 2013)

8V71 said:


> 1/4 percentage wise I believe.


8.94/120*100= 7.45%
4.47/240*100= 1.86%

Im sorry Speedy  when 8V71 posted that I realized I misunderstood what you were saying, like I said I wasn't arguing.


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## Speedy Petey (Jan 10, 2007)

I didn't take it that way at all. I knew where you were coming from. 
The others explained it perfectly, that's what I was referring to.


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## Bugz11B (May 12, 2013)

Speedy Petey said:


> I didn't take it that way at all. I knew where you were coming from.
> The others explained it perfectly, that's what I was referring to.


also thanks! although math wise I guess I already knew the formulas, I think I always automatically assumed 1/2 as severe. After a friendly back an forth I will never forget its a 1/4 as severe.


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## erics37 (May 7, 2009)

sbrn33 said:


> Is running a motor at a higher voltage better for the motor? Is it more efficient?


The motor generally doesn't care but in this case doubling the voltage cuts the current in half which eliminates some of the voltage drop effect and in the end very well may slightly improve motor performance.


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## BBQ (Nov 16, 2010)

FastFokker said:


> Rhetorical question, I'm guessing.. you must know. lol
> 
> I don't actually know, but wouldn't 240V and a lower current going through the windings make a motor last longer?


It does not change the current in the windings.


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## RGH (Sep 12, 2011)

Now FWIW after you reconfigure your project ....call a few supply houses in your area and look on line.....the gfic ocd you need can most like be had for under a hundo....I purchased a siemans 30a2pole gfic a few weeks ago for $85 at my local supplier....:thumbsup:...and try and stay away from uf...pipe (sch 80 pvc)and thw here would not break the bank...good luck and let us know what and how you did it....pics !!!!.....you know so we can rip you after:laughing:....(we all get it here).


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## Mdelectrician (Nov 16, 2011)

Thanks guys. Yes i am an electrician. Been out of the game for awhile and my code, formulas are lacking a little. I come here to learn and ask questions. Plus i have never really messed with piers that much. more of just a house mouse. So for the people giving helpful advice thank you!


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