ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Ground Rods: Installation and Hook-Up
by renosteinke - 11/26/22 07:28 PM
Happy Thanksgiving all!
by Bill Addiss - 11/24/22 08:37 AM
Colt Firearms Switchbox
by sabrown - 11/22/22 01:33 PM
Perfect work light?
by gfretwell - 11/22/22 12:48 AM
copper prices where you live and inflation
by gfretwell - 11/21/22 01:52 PM
New in the Gallery:
240/208 to a house
240/208 to a house
by wa2ise, October 9
Now you know.
Now you know.
by Tom_Horne, September 7
Who's Online Now
0 members (), 36 guests, and 52 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#12897 08/20/02 10:22 PM
Joined: Apr 2002
Posts: 914
E
Member
Help! I'm working on a bid and my "handy" electric calculator is giving me conflicting answers on wire size for a long run. The run is almost 400 feet(up and down included) from the main panel to the sub panel. 100 amps 120/208 3 phase. Using copper THHN and 3% VD, what size wire?
While we're at it, how much would you bid? Most of the run is 25ft in the air and you need to add 3 30 amp 3 phase outlets to plug in equipment near the new sub. The panels are seimens bolt in and the conduit needs to bew EMT, you provde the lift. Thanks!

Joined: Apr 2002
Posts: 21
J
jo Offline
Member
10,700 #2 wire 2"emt

Joined: Jul 2002
Posts: 74
S
Member
With a full load and 3.1% you need to run a 2/0. 3/0 gets you douwn to a 2.5% v/d..
To early in the morning to help with the quote..
SC John.

Joined: Dec 2000
Posts: 4,289
Member
Ditto SCJohn,
2.55% VD with 3/0
2" EMT

Joined: Apr 2002
Posts: 21
J
jo Offline
Member
Sorry
3/0 is correct

Joined: Jan 2002
Posts: 163
D
Member
Feedback please - these VD calculations to determine the need for 3/0 conductor is based on a 100A draw - in truth this panel will not be pulling 100A...prob. won't even be pulling 90A....if you use 90A in your calculation your conductor size drops to 2/0. Not only does this lower the matl. cost it sure makes pulling into that 2" conduit a lot easier. My opinion is this: if you're going to be pulling more than 80A from a 100A panel, you should be upsizing it to begin with.

Joined: May 2001
Posts: 717
G
Member
Your calculation is based on Article 220. That is where your amps for your VD calc should come from.

Joined: Apr 2002
Posts: 914
E
Member
Thanks to everyone! My ElectriCalc was telling me 3/0 CU, but I didn't want to believe it. I mean 4/0 AL is good for 200. The actual run is more like 370ft and I can live with just over 3%VD, so I did the quote with 2/0, although my gut tells me that they will never pull more than 50 or 60 amps in which case #1CU would be fine. I gave the bid the way I would want it, if I lose it to someone using #1 or #2, then so be it. Thanks Guys

Joined: Dec 2000
Posts: 4,289
Member
George is right. Use 220, not your gut feeling (I thought you said 100 amp load). [Linked Image]

Joined: Apr 2002
Posts: 914
E
Member
electure, I ignored my gut feeling and went with the max, but I doubt my competion did, that's what I was saying. Acutally when you add the 3 pieces of equipment, the total max amps is 58 (22,22&14) and will all run at the same time. But this is for a 100 amp sub panel and someone in the future could add more equipment or even another sub panel off of this one. Therefore I wanted to make sure the wire could handle max load without substanial VD.


Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *
2023 National Electrical Code (NEC)
2023 NEC Now Available!
 
* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
watersparkfalls
watersparkfalls
Washington...Not DC
Posts: 240
Joined: March 2005
Top Posters(30 Days)
NORCAL 3
Trumpy 3
Popular Topics(Views)
300,233 Are you busy
229,958 Re: Forum
214,779 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5