ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Recall Notice Kidde Smoke Alarms
by dougwells. 03/22/18 01:40 PM
by HotLine1. 03/22/18 09:08 AM
Recall notice: Southwire wi-fi wall switches
by sparkyinak. 03/15/18 06:03 PM
Goodman Manufacturing Recalls Modular Blowers
by Admin. 03/13/18 10:40 PM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
0 registered members (), 40 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Outdoor transformer/grounding question #217353
06/23/16 02:10 AM
06/23/16 02:10 AM
Sparky42  Offline OP
New Member
Joined: Jun 2016
Posts: 2
Application is an outdoor 30kVA, 480V/400V step down delta-wye transformer to be located within 10 feet of a building panel breaker box. The box has three phase 480V fused power and an input ground wire tied to the breaker box via a screw lug. The output is a 3P4W IEC-309 receptacle, the ground pin of the receptacle has a wire that screws into the breaker box. My question is: Can I use the receptacle ground wire to be the ground for the transformer chassis and X0 of the secondary (via a terminal bar inside and bonded to the transformer enclosure)? Or will I have to run a ground wire independent of the receptacle so that ground is always made regardless of if the plug is in the receptacle. I could not find this detail in NEC.

2017 / 2014 NEC & Related Books and Study Guides
Re: Outdoor transformer/grounding question [Re: Sparky42] #217354
06/23/16 03:20 AM
06/23/16 03:20 AM
gfretwell  Offline

Joined: Jul 2004
Posts: 9,186
I suppose you need to back up and see if that transformer is listed for cord and plug connection. If that is OK, I suppose the pin in the plug is sufficient to establish the ground.
Those 309 plugs are designed so the ground makes before the ungrounded pins.

Greg Fretwell
Re: Outdoor transformer/grounding question [Re: Sparky42] #217387
07/01/16 12:59 AM
07/01/16 12:59 AM
Yoopersup  Offline
Joined: Mar 2003
Posts: 840
Read 2014 N.E.C. 250.30 (C)

Re: Outdoor transformer/grounding question [Re: Sparky42] #217393
07/05/16 12:09 AM
07/05/16 12:09 AM
Sparky42  Offline OP
New Member
Joined: Jun 2016
Posts: 2
Hmmm, the breaker box is mounted on a metal building. Can I consider the breaker box as the source location? In that case there is a ground wire connected to the breaker box itself (and it comes out via the IEC-309 connector). This is not a permanent installation it will only be active for a month or so.


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


Member Spotlight
Posts: 27
Joined: December 2004
Show All Member Profiles 
Top Posters(30 Days)
Admin 5
Trumpy 5
Popular Topics(Views)
244,860 Are you busy
181,981 Re: Forum
172,016 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.023s Queries: 15 (0.005s) Memory: 0.9596 MB (Peak: 1.0912 MB) Zlib enabled. Server Time: 2018-03-23 05:11:52 UTC