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Old 01-02-2011, 02:52 PM   #1
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length of run?


Is it safe to use a 200foot run of 12-2 with ground in a 1/2 inch conduit to run all the power needs of a 2005 or newer full sized expensive motor coach. I moved in a place and we are both on the same meter and the power bill is sky high and I use very little power and they are and elderly retired couple home all day is this because of the voltage drop to them or something else.

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Old 01-02-2011, 02:54 PM   #2
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length of run?


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Is it safe to use a 200foot run of 12-2 with ground in a 1/2 inch conduit to run all the power needs of a 2005 or newer full sized expensive motor coach. I moved in a place and we are both on the same meter and the power bill is sky high and I use very little power and they are and elderly retired couple home all day is this because of the voltage drop to them or something else.
First how many amps does the motor coach require?

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Old 01-02-2011, 03:02 PM   #3
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length of run?


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First how many amps does the motor coach require?
Ditto
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Old 01-02-2011, 03:05 PM   #4
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length of run?


120v or 240v ?
Where are you located ?
Many RV's need 240v, seems a 30a 240v is pretty standard
#12 wire @200' with a 20a load will lose around 12.8% to voltage drop over that distance
With a 10a load it will still lose over 6%
Usually you want voltage drop down under 3%
That equals under a 5a load for your distance
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Old 01-02-2011, 03:19 PM   #5
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length of run?


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Originally Posted by Scuba_Dave View Post
120v or 240v ?
Where are you located ?
Many RV's need 240v, seems a 30a 240v is pretty standard
#12 wire @200' with a 20a load will lose around 12.8% to voltage drop over that distance
With a 10a load it will still lose over 6%
Usually you want voltage drop down under 3%
That equals under a 5a load for your distance
Correct on the 3%

120volts- no more than 3.6 voltage drop is acceptable
240volts- No more than 7.2.voltage drop is acceptable

Last edited by Sfeyelectric; 01-02-2011 at 03:21 PM.
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Old 01-02-2011, 03:29 PM   #6
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length of run?


assuming it is the higher figure somewhere around 13% drop is there a way to calculate approximately how much more electricity they are using by not using the proper size wire for that run
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Old 01-02-2011, 03:31 PM   #7
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length of run?


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Originally Posted by DUMMYDIYer View Post
assuming it is the higher figure somewhere around 13% drop is there a way to calculate approximately how much more electricity they are using by not using the proper size wire for that run
If you can give us the answer to how many amps it requires, we can help you come up with the proper wire size and breaker for this!
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Old 01-02-2011, 03:57 PM   #8
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length of run?


13% is nearly 15 volts.about one 100 watt lite and you are done.if it runs off of 120,you will need at least #8 wire.that is a little over 6volt drop at 20 amp.
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Old 01-02-2011, 03:59 PM   #9
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length of run?


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13% is nearly 15 volts.about one 100 watt lite and you are done.if it runs off of 120,you will need at least #8 wire.that is a little over 6volt drop at 20 amp.
Can not exceed 3.6 volt drop on 120
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Old 01-02-2011, 04:06 PM   #10
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length of run?


As an example
For a 200' run for a 20a circuit you would need #6 wire for 3.2% voltage drop with 120v
For a 240v run (sub panel etc) #10 wire would give you a 4% drop
But that is still a 9.6v drop, that could cause a problem

We had a partial power loss here
We were only getting 90v to outlets
Lights still worked....but they were dim
Its motors you need to worry about
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Old 01-02-2011, 04:09 PM   #11
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thats right.so just move the motor home 60 feet closer or go with #6 and that is about 3.9%.
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Old 01-02-2011, 04:09 PM   #12
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length of run?


#8 is what I would use at that drop if only 120v, with #6 for the ground. Since you are going to need a disconnect at the end, and it would have to be 4 wire under the new NEC code, I would go no less than 3 #6 for the run, and 1 #4 for the ground at that distance from the Main to the disconnect. You can always go with #12 for 120, or #10 if 240 from the disconnect to the outlet.
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Old 01-02-2011, 04:14 PM   #13
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length of run?


where did you get #4 for ground?
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Old 01-03-2011, 12:32 PM   #14
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length of run?


why the larger ground???? this is the opposite of what is required and prudent.
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Old 01-03-2011, 02:17 PM   #15
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length of run?


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Originally Posted by gregzoll View Post
#8 is what I would use at that drop if only 120v, with #6 for the ground. Since you are going to need a disconnect at the end, and it would have to be 4 wire under the new NEC code, I would go no less than 3 #6 for the run, and 1 #4 for the ground at that distance from the Main to the disconnect. You can always go with #12 for 120, or #10 if 240 from the disconnect to the outlet.
I am also confused. can you explain all this for us.
What new code requires a disconnect based on wire size? And why are you spec'ing a larger ground than the circuit conductors?


BTW, a motor coach will almost definitely require a 50A-120/240v 4-wire feed for best efficiency and usage. At least that is what the input would be.

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