ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Potseal 11
Recent Posts
600 KW 120/208 3 Phase Y protection
by Yooperup. 07/24/17 12:20 PM
1913 American Electrician's Handbook
by gfretwell. 07/20/17 01:08 PM
Green House wiring
by ghost307. 07/20/17 09:10 AM
Permit Snafus...AHJs and Contractors Jump in
by HotLine1. 07/18/17 08:06 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
239,308 Are you busy
174,773 Re: Forum
167,141 Need opinion
Who's Online Now
0 registered members (), 72 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#12897 - 08/20/02 11:22 PM Quick wire size question.  
Electric Eagle  Offline
Member
Joined: Apr 2002
Posts: 914
Alpharetta, GA
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!


Work Gear for Electricians and the Trades

#12898 - 08/20/02 11:58 PM Re: Quick wire size question.  
jo  Offline
Member
Joined: Apr 2002
Posts: 21
Oakland, California
10,700 #2 wire 2"emt


#12899 - 08/21/02 06:00 AM Re: Quick wire size question.  
scjohn  Offline
Member
Joined: Jul 2002
Posts: 74
charleston, SC, USA
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.


#12900 - 08/21/02 08:27 AM Re: Quick wire size question.  
electure  Offline


Member
Joined: Dec 2000
Posts: 4,260
Fullerton, CA USA
Ditto SCJohn,
2.55% VD with 3/0
2" EMT


#12901 - 08/21/02 10:15 AM Re: Quick wire size question.  
jo  Offline
Member
Joined: Apr 2002
Posts: 21
Oakland, California
Sorry
3/0 is correct


#12902 - 08/21/02 10:38 AM Re: Quick wire size question.  
dana1028  Offline
Member
Joined: Jan 2002
Posts: 163
San Carlos, CA
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.


#12903 - 08/21/02 10:53 AM Re: Quick wire size question.  
George Corron  Offline
Member
Joined: May 2001
Posts: 717
Lorton, Va USA
Your calculation is based on Article 220. That is where your amps for your VD calc should come from.


#12904 - 08/21/02 09:36 PM Re: Quick wire size question.  
Electric Eagle  Offline
Member
Joined: Apr 2002
Posts: 914
Alpharetta, GA
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


#12905 - 08/21/02 10:02 PM Re: Quick wire size question.  
electure  Offline


Member
Joined: Dec 2000
Posts: 4,260
Fullerton, CA USA
George is right. Use 220, not your gut feeling (I thought you said 100 amp load). [Linked Image]


#12906 - 08/21/02 10:26 PM Re: Quick wire size question.  
Electric Eagle  Offline
Member
Joined: Apr 2002
Posts: 914
Alpharetta, GA
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.



Member Spotlight
AllClear
AllClear
Belmond Iowa US
Posts: 44
Joined: August 2005
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.015s Queries: 14 (0.003s) Memory: 0.8078 MB (Peak: 0.9816 MB) Zlib enabled. Server Time: 2017-07-24 22:50:13 UTC