Voltage drop to dedicated receptacles

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minesh21

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CA USA
I have an issue where we need to design for (4) receptacles each having 4A on (1) 20A circuit. That means 4A per receptacle (this is the requirement). Problem is we don't have power nearby and have to run 300 ft. When I do a voltage drop calculation, even with #10 (or #8), conductors I have a huge voltage drop. This is expected since we are 120V, but I'm unsure about the current value that should be used. Title 24 (California job) requires you to use the furthest receptacle, but I don't know if I should be using the furthest receptacle at the full 16A load, or just use the draw of the individual receptacle at 4A.

I'm guessing this depends on how the contractor wires it right? If they daisy chain everything then I would depend on where the homerun occurs and how far that is correct?
 
K8MHZ said:
How about a MWBC home run feeding 8 amps per side? #10 would be 4%.
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Yes I could do that but that would require twice the amount of conductors to the area. I'm consider either splicing the circuit near the source panelboard and running multiple conductors to reduce the voltage drop, or just using more circuit breakers to feed the loads.
 
minesh21 said:
I'm guessing this depends on how the contractor wires it right? If they daisy chain everything then I would depend on where the homerun occurs and how far that is correct?
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That is correct. You only need to figure the full 16A for the part of the circuit that is carrying it, possibly just the home run to the first recpt, then 12A to the second one.....
minesh21 said:
Yes I could do that but that would require twice the amount of conductors to the area. I'm consider either splicing the circuit near the source panelboard and running multiple conductors to reduce the voltage drop, or just using more circuit breakers to feed the loads.
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???

For single phase you would only be adding one more wire to make a MWBC. How is that twice as much wire, and how is running more circuits saving any materials?
 
ActionDave said:
That is correct. You only need to figure the full 16A for the part of the circuit that is carrying it, possibly just the home run to the first recpt, then 12A to the second one.....
???

For single phase you would only be adding one more wire to make a MWBC. How is that twice as much wire, and how is running more circuits saving any materials?
Click to expand...

Its confusing I know. What I'm saying is I would put the homerun near the source, to reduce the distance of the full 16A. Then run one hot and one neutral to (2) receptacles, and another hot/neutral to the other two. Therefore, the actual current that I use for voltage drop is only 8A instead of 16A.
 
How are you all coming up with #8 only allowing a 3% drop at 300ft and 120v at 16 amps?



JAP>
 
K8MHZ said:
Or only counting the length of the run (300') not the length of the conductors (600').
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If you did that would it not make the conductor even larger than #8 ? which I don't see how 8 would be large enough in the 1st place at 300' in this scenario.

JAP>
 
jap said:
If you did that would it not make the conductor even larger than #8 ? which I don't see how 8 would be large enough in the 1st place at 300' in this scenario.

JAP>
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hbiss was the one that had the low voltage drop calculation.

I get #8 for a 3% voltage drop. What's the problem with that?

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This is what I get using 150' of run, which is 300' of conductor.

1 conductors per phase utilizing a #8 Copper conductor will limit the voltage drop to 2.77% or less when supplying 16.0 amps for 150 feet on a 120 volt system.
 
K8MHZ said:
hbiss was the one that had the low voltage drop calculation.

This is what I get using 150' of run, which is 300' of conductor.

1 conductors per phase utilizing a #8 Copper conductor will limit the voltage drop to 2.77% or less when supplying 16.0 amps for 150 feet on a 120 volt system.
Click to expand...

Do you mind if I asked what formula you are using to come up with that answer?

JAP>
 
jap said:
Do you mind if I asked what formula you are using to come up with that answer?

JAP>
Click to expand...

I used an on line calculator. All the ones that I found used circuit length that had the two conductors already factored in. If hbiss was using a calculator or calculation that did not factor in both the hot and the neutral, the effect would be the same as halving the length of a two wire circuit.

Since his figures are very close to a 150' run that considers both conductors, I was thinking he didn't take the fact into consideration that there were two conductors that needed to be figured in. I remember this happening to many students in my apprenticeship on tests.
 
K8MHZ said:
I used an on line calculator. All the ones that I found used circuit length that had the two conductors already factored in. If hbiss was using a calculator or calculation that did not factor in both the hot and the neutral, the effect would be the same as halving the length of a two wire circuit.

Since his figures are very close to a 150' run that considers both conductors, I was thinking he didn't take the fact into consideration that there were two conductors that needed to be figured in. I remember this happening to many students in my apprenticeship on tests.
Click to expand...

Yup that was my next guess. With single phase loads you multiply times 2, for 3 phase you multiply times 1.73. Although most calculators ask you for the ONE WAY distance of the run, because they automatically multiply times 2 for you...

To clarify I wasn't the one that got the low voltage drop. It was another user.
 
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