Crossboss
Member
- Location
- Oklahoma city
- Occupation
- Journeyman wireman
For runs longer than 75 feet I need to upsize my wire? Can I pull #12 for the first 75' then upsize to #10. Is that an acceptable practice?
Voltage drop upsizing
- Thread starter Crossboss
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician
If you're using two different size conductors in the run it doesn't matter where the larger conductors are installed. Almost all of the time I see the larger conductors beginning at the source.
Welcome to the Forum.
Welcome to the Forum.
AC\DC
Senior Member
- Location
- Florence,Oregon,Lane
- Occupation
- EC
That’s not really correct, depends on your end load and percentage of voltage drop.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I am guessing that is a spec. on the plan
GeorgeB
ElectroHydraulics engineer (retired)
- Location
- Greenville SC
- Occupation
- Retired
HUH? If I have 75' of #12 and 75' of #10, it matters not in what order they are connected; indeed, if we ignore splicing resistance, I can have 75 1' lengths of each with 149 splices and the voltage drop will be the same as with one 75' #10 and one 75' #12. The order is insignificant.
Dsg319
Senior Member
- Location
- West Virginia
- Occupation
- Wv Master “lectrician”
He
When he said that’s not really correct. Maybe he was meaning the upsizing the conductors because of the given footage? As in possibly not needing to upsize the conductors depending on the load that will be at the end of the circuit.
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
That statement is fundamentally incorrect. Code doesn't require upsizing for voltage drop. The answer to the implied question however, is much more complex. Do you understand ohms law completely? Please don't be offended by this question and don't feel you need to say yes here if you don't we are quite gentle to those who are looking to learn.
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
You really missed the mark here. Voltage drop relies on amperage, and resistance. Resistance depends on wire size, material and length. So Dennis, as usual is 100% correct wen he says, "depends on your end load and percentage of voltage drop." End load is the amperage you need for the above, percentage is obviously the accept or reject criteria. Your statement is not germane to his, even though it is correct.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
My point is 75 feet is not usually long enough to be an issue with voltage drop. I suspect this was a spec on the plans for that reason.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
The response by AC/DC was to the OP stating that the run was over 75' then it needed to be increased in size.
AC\DC
Senior Member
- Location
- Florence,Oregon,Lane
- Occupation
- EC
Plus what voltage is it. If it’s 120 v then you might have to (depending on load). But I bet for 240 volt and higher no problem, for that length.
Fred B
Senior Member
- Location
- Upstate, NY
- Occupation
- Electrician
Applying the assumption based on OP statement regarding a 12awg wire 75ft length, extrapolate that it is for 20A, pluging into southwire app,
20A, 120V, 75ft, if you desire not more than 3% VD, the results will require a 10AWG with 2.84% VD,
if you look for 5% max VD a 12AWG will result in 4.51%
even at 15A, 120V, 75ft, for 3%VD is still 10AWG with 2.13%VD; 5% max VD results 12AWG, at 3.39%VD
If your criteria is for 240V, 20A, 75ft, 3% max VD results with 12AWG is 2.26%VD.
Overall what your desired voltage drop you are looking to acheive or for equipment operating requirements would dictate how much you increase in conductor sizing.
I would have never thought 75ft would have been enough length to possibly have conductors increase for VD.
Is this what initiated the requirements in (2017) 210.12(A)(3)(b) and 210.12(A)(4)(b) that restricts the length of 14AWG and 12AWG from overcurrent device to first outlet? 50ft for 14AWG and 70ft for 12AWG.
20A, 120V, 75ft, if you desire not more than 3% VD, the results will require a 10AWG with 2.84% VD,
if you look for 5% max VD a 12AWG will result in 4.51%
even at 15A, 120V, 75ft, for 3%VD is still 10AWG with 2.13%VD; 5% max VD results 12AWG, at 3.39%VD
If your criteria is for 240V, 20A, 75ft, 3% max VD results with 12AWG is 2.26%VD.
Overall what your desired voltage drop you are looking to acheive or for equipment operating requirements would dictate how much you increase in conductor sizing.
I would have never thought 75ft would have been enough length to possibly have conductors increase for VD.
Is this what initiated the requirements in (2017) 210.12(A)(3)(b) and 210.12(A)(4)(b) that restricts the length of 14AWG and 12AWG from overcurrent device to first outlet? 50ft for 14AWG and 70ft for 12AWG.
Crossboss
Member
- Location
- Oklahoma city
- Occupation
- Journeyman wireman
Yes it is in the specs for runs longer than 75 to upsize.
Crossboss
Member
- Location
- Oklahoma city
- Occupation
- Journeyman wireman
Yes it is on specs for runs longer than 75' use #10
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Pretty standard specification. On our current project they want it upsized after 85'.
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