Receptacle VD

A

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
Trying to figuring voltage drop some are more that 400' away. Not sure what I would use for current at end of run?

If I had (4) outdoor receptacles feed from same circuit and 1st 400' away and others 50' apart further would I use 180 va per receptacle then divide by voltage?
 
If I had no other information, I'd go with 180 va per receptacle.

But really I'd ask the customer what they intend to plug in. If those receptacles are for running holiday lights that is one thing; if they are for running yard equipment that is quite another.
 
winnie said:
If I had no other information, I'd go with 180 va per receptacle.

But really I'd ask the customer what they intend to plug in. If those receptacles are for running holiday lights that is one thing; if they are for running yard equipment that is quite another.
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Sorry meant to reply to you above
 
Exactly. If you don't know the actual load, your voltage drop will just be a guess. If you take worst case scenarios (say 16A of load on a 20A circuit) you end up with huge conductors and high prices. If you go with reasonable size conductors and they plug in large loads, then you get huge voltage drop.
 
So my next question is say I need to run out #4's for receptacles as they a long distance. Obviously I'm not terminating that size on the device.

At what point/distance am I allowed to drop to #12's or #10's? In this case I have (4) receptacles as stated above. All on same circuit.
 
Years ago I used ohms law to figure out voltage drop to ten drive way post luminare. The first luminare was 150' from the house then every one hundred feet. Had my coworker pull #10 TWNN to first luminare then #12 to maybe the next 5 luminaries then #14 wire for remainder. When the voltage at the panel was 119 volts the last luminare had 108 volts. Think the ohms law for DC was within 1.5 volts of my calculations. If it was my house or property I would provide wire heavy enough to be able to supply 16 Amps from a 20 amp breaker. Aluminum wire would be a lot cheaper. Should not have over a total of 5% voltage drop or 114 volts at furthest point.
 
garbo said:
Years ago I used ohms law to figure out voltage drop to ten drive way post luminare. The first luminare was 150' from the house then every one hundred feet. Had my coworker pull #10 TWNN to first luminare then #12 to maybe the next 5 luminaries then #14 wire for remainder. When the voltage at the panel was 119 volts the last luminare had 108 volts. Think the ohms law for DC was within 1.5 volts of my calculations. If it was my house or property I would provide wire heavy enough to be able to supply 16 Amps from a 20 amp breaker. Aluminum wire would be a lot cheaper. Should not have over a total of 5% voltage drop or 114 volts at furthest point.
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So I don't get the concept of why, at some point, you can reduce the wire size if you've started with larger wire?
 
Voltage drop is caused by the resistance of the wire. Each foot of wire is in series with all the rest. So if you have 1000 feet of #4 wire (0.25 ohms/1000 feet for 0.25 ohms) in series with 10 feet of #12 wire (1.6 ohms/1000 feet for 0.016 ohms) you get a total resistance of 0.266 ohms.

You can happily have a few feet of #12 at the beginning of the run (to connect to the breaker) and a few feet of #12 at the end (to connect to the receptacles).

If part of the circuit only carries part of the load current, then you can use fat wire for the part of the circuit carrying all the current, and thinner wire for the part of the circuit only carrying part of the current.

-Jonathan
 
Alwayslearningelec said:
So my next question is say I need to run out #4's for receptacles as they a long distance. Obviously I'm not terminating that size on the device.

At what point/distance am I allowed to drop to #12's or #10's? In this case I have (4) receptacles as stated above. All on same circuit.
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If you have no idea what the future load is I would just pull #10's. Absent some clarification like a note on the drawings as to what the load is no one can say even if #12 is too small.
 
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