Voltage Drop

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KRG9729

Member
Location
New York
I am working on a new 17,000sq. ft. box store and have an issue with sizing the homeruns. The estimator for the project sized the home runs in 10 AWG. However some of the homeruns are over 250'. The job was priced for utilizing #10 homerun MC cable. My concern is that on some of the longer LED track lighting homeruns that voltage drop may be an issue. The calculated loads average approx. 10 amps at 120 volt.

In order to upsize the homeruns we will have to run EMT which was not figured for the job.

I recall speaking with an engineer we work with that 5% voltage drop for lighting wouldn't be a problem.

Any suggestions or recommendation will be helpful.

Thank you.
 
T

topgone

Senior Member
Not much to work on, but granting what you've posted is correct, you have a 130 x 130 feet store. Maybe you need to re-route your wire run because a 130 wall length would mean twice that of 130 feet = 260 feet going by the walls to that other corner of the store! If you can, anchor your EMT's just above the ceiling and run it diagonally to the other end (max. run = 183 feet, the diagonal) you won't go over the voltage drop limits!

But if you have measured some runs and saw 250 feet; at 10 amps load, your VD will be 5.2%! Can you live with that?
 
Dennis Alwon

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
precise8128 said:
I got 6.1 VD the maximum allowance per code is 3% correct?
Click to expand...


The 3% or 5% is only a recommendation and not a code issue unless we are talking fire pumps.

210.19 Informational Note 4. Info notes are not code requirements

Informational Note No. 4: Conductors for branch circuits
as defined in Article 100, sized to prevent a voltage drop
exceeding 3 percent at the farthest outlet of power, heating,
and lighting loads, or combinations of such loads, and
where the maximum total voltage drop on both feeders and
branch circuits to the farthest outlet does not exceed 5 percent,
provide reasonable efficiency of operation. See Informational
Note No. 2 of 215.2(A)(1)(b) for voltage drop on
feeder conductors.
Click to expand...
 
F

Fitzdrew516

Senior Member
Location
Cincinnati, OH
Dennis Alwon said:
The 3% or 5% is only a recommendation and not a code issue unless we are talking fire pumps.

210.19 Informational Note 4. Info notes are not code requirements
Click to expand...

Not NEC, but 2% on feeders and 3% on branch circuits is a requirement of the energy code - I believe New York is on 2007's 90.1 (assuming the job is in the same location you are).
 
Smart $

Smart $

Esteemed Member
Location
Ohio
I figure 120V, 10A, #10 Cu, 250', steel conduit (or armor) at exactly 5% voltage drop.

LED lighting is usually quite voltage tolerant.

Bring it up with the boss and you've done your duty no matter which way it goes... but I wouldn't worry about it unless my name is on the truck.
 
luckylerado

luckylerado

Senior Member
Location
Lake of the Ozarks
Fitzdrew516 said:
Ashrae Standard 90.1-2007 -

8.4.1.1 - Feeders Feeder conductors shall be sized for a maximum voltage drop of 2% at design load.
8.4.1.2 - Branch Circuits. Branch circuit conductors shall be sized for a maximum voltage drop of 3% at design load.
Click to expand...

This reads differently now. 90.1 2015 supplement to 2013

8.4.1 Voltage Drop. The conductors for feeders and branch
circuits combined shall be sized for a maximum of 5% voltage
drop total.

Section 8.4.1 previously separated feeder conductors
from branch circuits when limiting voltage drop. By specifying
the same combined voltage drop over the combination of
components, this addendum reduces first costs in certain projects
while remaining neutral on energy costs.
 
F

Fitzdrew516

Senior Member
Location
Cincinnati, OH
luckylerado said:
This reads differently now. 90.1 2015 supplement to 2013

8.4.1 Voltage Drop. The conductors for feeders and branch
circuits combined shall be sized for a maximum of 5% voltage
drop total.

Section 8.4.1 previously separated feeder conductors
from branch circuits when limiting voltage drop. By specifying
the same combined voltage drop over the combination of
components, this addendum reduces first costs in certain projects
while remaining neutral on energy costs.
Click to expand...

Yep - I was referring to the 2007 edition due to the location of the OP. Not sure if anywhere is using the 2015 version yet. It usually takes a few years to catch on in most places.
 
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