need answer on voltage drop

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pryan

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I have a 700 foot underground service circuit, 350 feet half way that will be carrying 100 amps, 240 volts, single phase. Do I also need to compensate for a voltage drop on the neutral wire (using aluminum wire )or just the line voltage wires?
 
pryan said:
I have a 700 foot underground service circuit, 350 feet half way that will be carrying 100 amps, 240 volts, single phase. Do I also need to compensate for a voltage drop on the neutral wire (using aluminum wire )or just the line voltage wires?
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If the load is fairly ballacned on the two non-grounded conductors then you should not have much current going through the neural, so voltage drop on it should not be an issue. e/m.
 
I wouldn't even try to answer the question without knowing something about what the load or loads are.
 
Physis 3 said:
I wouldn't even try to answer the question without knowing something about what the load or loads are.
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I totally agree. If this is for a panel with many 120 volt circuits then I would upsize my neutrals. If you have mostly 240 volt circuits then there may be no need to upsize the neutral.
 
If you have any 120V motors of any size (over 1/4HP), I'd greatly increase the size of the neutral, maybe even bigger than the phase conductors.

If you use a standard size neutral, and you have one of those '5HP, runs on standard house current' air compressors, half of the lights will get very dim, the other half very bright when it starts. Even a washing machine will cause trouble.

240V loads will have no effect on the neutral.
 
Dennis Alwon said:
I totally agree. If this is for a panel with many 120 volt circuits then I would upsize my neutrals. If you have mostly 240 volt circuits then there may be no need to upsize the neutral.
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Regardless, the answer to the question would still be: yes, voltage drop on the neutral must be considered, especially when it is sized to handle only the maximum imbalance between itself and any one ungrounded conductor.

However, if the service is run with a neutral equal in ampacity to that of the ungrounded conductors, there would be no need to even bother with the calculation.
 
pryan said:
Do I also need to compensate for a voltage drop on the neutral wire (using aluminum wire )or just the line voltage wires?
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Do you have to compensate for voltage drop on the line conductors? Not that I wouldn't, but do you have to?

Edit:

I read what I said and it sounds a little harsh, but being that you know enough to ask the question, and how you did, I'm pretty confident that you can also answer it. And that means a lot.
 
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If you have any 120V motors of any size (over 1/4HP), I'd greatly increase the size of the neutral, maybe even bigger than the phase conductors.
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May I ask why...AMPS=AMPS, 10 amps in a single phase (speaking strictly 2 wire OK 3 wire with the EGC) L1/hot/energized conductor will be the same 10 amps in the grounded/neutral conductor, the copper does not know the difference
 
danickstr said:
if you upsize the UC's you have to upsize the neutral and Grounding conductor.
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Grounding conductor yes, neutral no. :)

danickstr said:
i do not agree with the plumbing analogy given, because of the OCPD acting as a 3/4" ball valve
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In the event of a ground fault, where the OCPD would be attempting to instantaneously interrupt the circuit in the magnetic portion of the circuit breaker, that '3/4" ball valve' is going to behave very similar to the '4" ball valve' in that scenario - but I like the way you think. :cool:

Thanks for the feedback. :)
 
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