ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Video: Inventor of the GFCI self-testing shocks
by Bill Addiss. 01/17/18 11:11 PM
FPE in Germany
by HotLine1. 01/17/18 07:07 PM
VDE 0100 to introduce AFCIs
by LongRunner. 01/17/18 10:32 AM
Fujifilm Recalls Power Adapter Wall Plugs
by Admin. 01/16/18 07:04 PM
Air Compressor feeder conductor sizing
by Potseal. 01/15/18 09:08 PM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
0 registered members (), 26 guests, and 10 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Transformer Installations and Vibration #85627
07/23/03 07:52 AM
07/23/03 07:52 AM
Joe Tedesco  Offline OP
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
Transformers are typically wired with flexible metal conduits and we know that is usually not considered as a problem.

Question: An installer wired the primary of a transformer with a 2 inch EMT, and used a 4 inch EMT out for the secondary supply.

Does the NECĀ® have any rule that could be cited, or would the specifications, or the instructions require flexible connections?

Joe Tedesco, NEC Consultant
2017 / 2014 NEC & Related Books and Study Guides
Re: Transformer Installations and Vibration #85628
07/23/03 08:05 AM
07/23/03 08:05 AM
Ron  Offline
Joined: Mar 2002
Posts: 582
White Plains, NY
Job specs only would dictate a flex requirement. No NEC requirement that I know of.

Re: Transformer Installations and Vibration #85629
07/23/03 08:40 AM
07/23/03 08:40 AM
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
I only get 9 "hits for vibration in the 2002 NEC, none of which seem to apply.

368.28 (Bussways over 600 volts)

400.7 (Cords)

422.16 (Appliances)

545.13 (Manufactured Buildings)

550.16 (Mobile Homes)

551.30 (RVs)

551.47 (RVs)

552.48 (Park Trailers)

695.12 (Fire Pumps)

I looked in 450 and some raceway articles and could find no requirement to flex in transformers, I have done it with many different methods, pipe, trough, flex, etc.

What I found strange is no requirement to use a flexible method to a motor.

Bob Badger
Construction & Maintenance Electrician
Re: Transformer Installations and Vibration #85630
07/23/03 09:24 AM
07/23/03 09:24 AM
Joe Tedesco  Offline OP
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
Thanks for the quick reply, my student Elliot is happy now!

See 430.145 Method of Grounding.
Where required, grounding shall be done in the manner specified in Part V of Article 250.

(A) Grounding Through Terminal Housings. Where the wiring to fixed motors is metal-enclosed cable or in metal raceways, junction boxes to house motor terminals shall be provided, and the armor of the cable or the metal raceways shall be connected to them in the manner specified in Article 250.

FPN: See 430.12(E) for equipment grounding connection means required at motor terminal housings.

(B) Separation of Junction Box from Motor. The junction box required by 430.145(A) shall be permitted to be separated from the motor by not more than 1.8 m (6 ft), provided the leads to the motor are Type AC cable or armored cord or are stranded leads enclosed in liquidtight flexible metal conduit, flexible metal conduit, intermediate metal conduit, rigid metal conduit, or electrical metallic tubing not smaller than metric designator 12 (trade size ), the armor or raceway being connected both to the motor and to the box.
Liquidtight flexible nonmetallic conduit and rigid nonmetallic conduit shall be permitted to enclose the leads to the motor, provided the leads are stranded and the required equipment grounding conductor is connected to both the motor and to the box.

Where stranded leads are used, protected as specified above, each strand within the conductor shall be not larger than 10 AWG and shall comply with other requirements of this Code for conductors to be used in raceways.

Joe Tedesco, NEC Consultant


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


Member Spotlight
Bill Addiss
Bill Addiss
Posts: 3,890
Joined: October 2000
Show All Member Profiles 
Top Posters(30 Days)
sparky 20
Admin 20
Potseal 13
Popular Topics(Views)
243,539 Are you busy
180,341 Re: Forum
170,830 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.022s Queries: 14 (0.006s) Memory: 0.9599 MB (Peak: 1.0925 MB) Zlib enabled. Server Time: 2018-01-18 19:55:23 UTC