Voltage Drop

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heymitduh

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Hi all,
Gotta make this fast as work is waiting. Print calls for #6 Thhn Cu to feed an "IDF" panel. Approximately 150' away. Here's the issue. Panel stubs up into a trough or wireway. The 6's have been ran from this trough to the j-box above the IDF panel. Now I was going to drop 6's from the trough down to the distribution panel but was told by another j-man that I could run #12. (Distance btwn. trough and dist. panel approx. 30') He said that the voltage drop wouldn't appear in that distance. It just doesn't seem right to me. He was and is all prepared to show me why using the voltage drop formula. Your thoughts?
Mike
 
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FRANK ELECTRIC

Member
Location
PA
Short for intermediate distribution frame, a cable rack that interconnects and manages the telecommunications wiring between an MDF and workstation devices. Cables entering a building run through a centralized MDF, then each individual IDF and then on to specific workstations. For example, an enterprise that encompasses a building with several floors may have one MDF on the first floor and one IDF on each of the floors that is connected to the MDF.
 
GeorgeKoehl

GeorgeKoehl

Member
Location
Washington IL
based from an 2008 version of an ElectriCalc Pro

If you want to have a full 20 amps at the end of the 150' run
then the smallest wire you could have is #8 (4.1% VD)
if you used #6 you would have a VD of 2.6%

Based on a single phase 120v circuit at 90degrees
 
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RETRAINDAILY

Senior Member
Location
PHX, arizona
heymitduh said:
Hi all,
Gotta make this fast as work is waiting. Print calls for #6 Thhn Cu to feed an "IDF" panel. Approximately 150' away. Here's the issue. Panel stubs up into a trough or wireway. The 6's have been ran from this trough to the j-box above the IDF panel. Now I was going to drop 6's from the trough down to the distribution panel but was told by another j-man that I could run #12. (Distance btwn. trough and dist. panel approx. 30') He said that the voltage drop wouldn't appear in that distance. It just doesn't seem right to me. He was and is all prepared to show me why using the voltage drop formula. Your thoughts?
Mike
Click to expand...

You could and it probably be fine. But why would you want the hassle?
If there is a problem it would be your fault for not doing it as specked.
Here the inspector would fail you for not doing it as a the EE drew it.

I would do it just like the drawings show
 
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