ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
sparky 4
Recent Posts
Dimmable LED 2x4 lay in fixtures
by gfretwell. 12/13/17 09:49 PM
2017 NEC Changes
by sparky. 12/13/17 06:57 PM
Casino Wiring methods
by HotLine1. 12/09/17 10:44 AM
Ground wire Size to water Line.
by HotLine1. 12/05/17 12:11 PM
Flexible conduit to an outside Spa
by gfretwell. 12/05/17 12:28 AM
New in the Gallery:
Gallery Test
Popular Topics(Views)
243,036 Are you busy
179,453 Re: Forum
170,394 Need opinion
Who's Online Now
0 registered members (), 21 guests, and 7 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#97095 - 01/19/06 08:32 PM Conductor Size  
Sparky_1  Offline
Member
Joined: Nov 2004
Posts: 14
What is the smallest size feeder and neutral that I can use in this situation?

I have a fat storage tank that has a Control panel that feeds a 4500 watt / 240 volt heating element,
7 1/2 HP 3 phase motor 240 V (20.5 amps), fractional hp circulating pump 1/2 amp,
convenience outlet and light. Roughly 40 amps, with the nameplate of the fat tank control panel at 65 amps. ( The tank company stated that the 125% of FLA was listed on the FLA
sticker) The control circuit is fused down to 15 amps 120 volt.

We have 480 Volt 3 phase, so I set a 30 kva transformer feeding a 100 amp 240 Volt disconnect.
Can I feed this control panel with # 6 THHN fused at 70 amps and reduce the neutral to a # 12,or does it have to be a # 6?. Or do I have to run # 4s THHN to this unit?

[This message has been edited by Sparky_1 (edited 01-19-2006).]


2017 / 2014 NEC & Related Books and Study Guides

#97096 - 01/20/06 12:22 AM Re: Conductor Size  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,142
Estero,Fl,usa
If I was answering a question on a test I would say the #6 THHN fused at 70a (using the round up rule) with a #12 neutral serving 1 or 2 single pole 20a breakers on different phases is the minimum. I can't say that is the best design decision.


Greg Fretwell

#97097 - 01/20/06 05:51 PM Re: Conductor Size  
Sparky_1  Offline
Member
Joined: Nov 2004
Posts: 14
Everything worked out today, we ran # 6s with a separate 15 amp control circuit.
I threw a amp meter on the unit, the FLA was 41.
The inspector wants a sticker stating that is has two separate disconnects.



Member Spotlight
Samurai
Samurai
Fl.
Posts: 46
Joined: May 2007
Show All Member Profiles 
Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.010s Queries: 14 (0.003s) Memory: 0.7523 MB (Peak: 0.8731 MB) Zlib enabled. Server Time: 2017-12-14 08:07:58 UTC