ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

ECN Shout Chat
Top Posters(30 Days)
Admin 16
Recent Posts
ESA Arc flash course
by TheShockDoctors. 03/24/17 10:15 AM
fuse rejectors
by HotLine1. 03/24/17 07:53 AM
Another Forum Update
by Admin. 03/22/17 03:04 PM
Dining room plugs
by watersparkfalls. 03/21/17 10:31 PM
TRUE POWER
by jraef. 03/21/17 09:13 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
231,369 Are you busy
166,092 Re: Forum
160,560 Need opinion
Who's Online Now
0 registered members (), 59 guests, and 11 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#81577 - 08/30/02 10:34 PM 120/240V and 120V the same?  
sparky66wv  Offline
Member
Joined: Nov 2000
Posts: 2,232
West Virginia
Concerning the requirement to not mix voltages in conduit, I tend to think that it is OK to run, say a dryer circuit with a laundry circuit in the same conduit (assuming all other codes requirements are met), being all the same potential to ground, but another opinion by another EC was that it would be a violation.

Besides, 300.3(C)(1) says its OK, don't it?

[Linked Image]


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

2017 / 2014 NEC & Related Books and Study Guides

#81578 - 08/31/02 12:09 AM Re: 120/240V and 120V the same?  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
What requirement not to mix voltages? You are always permitted to mix power circuits as long as all conductors are rated for the maximum voltage in the raceway and the maximum voltage is 600 volts or less. It is not a code violation to have 120/240 circuits, 120/208 circuits and 480/277 circuits in the same raceway with each other. When you have control or signaling circuits, you can't, in general, mix them with power circuits. You need to apply Article 725 for those circuits.
Don


Don(resqcapt19)

#81579 - 08/31/02 01:49 PM Re: 120/240V and 120V the same?  
sparky66wv  Offline
Member
Joined: Nov 2000
Posts: 2,232
West Virginia
Another non-existant code I was brought up on... [Linked Image]

I wonder how it got started? The EC in question wasn't trained by Jim Hixson as Joe and I were... I even "remember" a clause on voltage to ground to include all poles of multiwire circuits and the like...

Weird.

Thanks for clearing me up, Don.


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

#81580 - 09/01/02 01:27 PM Re: 120/240V and 120V the same?  
tdhorne  Offline
Member
Joined: Mar 2001
Posts: 345
Maryland, USA
There is a code restriction against having devices in the same undivided box with voltages over three hundred between devices. This is often what folks are remembering when they think that different voltage systems can not be in the same conduit or raceway.

In my opinion it is best practice to keep different voltage systems separated in different raceways were practicable but the code does not require it.
--
Tom


Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous for general use" Thomas Alva Edison

#81581 - 09/01/02 02:17 PM Re: 120/240V and 120V the same?  
sparky66wv  Offline
Member
Joined: Nov 2000
Posts: 2,232
West Virginia
404.8(B)

Thanks, Tom. That very well may be the confusion as well as the control circuit angle. Both Mr Hixson and the EC that stated that it was a violation have had lots of industrial experience, and probably thought (wrongly) that the 725 requirements were for all circuits, probably learned by failing an inspection rather than reading it themselves. Just guessing a theory... (and wasting more cyberspace!)

[Linked Image]


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

#81582 - 09/03/02 04:02 AM Re: 120/240V and 120V the same?  
TE  Offline
Member
Joined: Aug 2002
Posts: 36
USA
I have heard this several times in the past.
I can't say for sure,but I have a couple of opinions as to why this comes up.

Opinion #1 Mis-interpretation

In article 300 there is a code:
Conductors of different systems- Conductors of high and low voltage shall not occupy the same wiring enclosures.
This code is actually under the sub-heading:
Requirements for Over 600 Volts,

Wiring over and under 600volts shall
(must) be seperated with a few exceptions.

I think maybe some have read this thinking it reffered to 120/208 as low voltage and 277/480 high voltage.

Conductors occupying the same raceway must have insulation rated at the highest voltage contained in that raceway. Therefore 120-208-240v would be covered by insulation rated at 300v, but if you read the writing on a piece of THHN it is rated for 600V.

Opinion #2 Because

My other idea is that this is something that has been taught and carried on as many things we are taught in the trade, without reference to actual codes or requirements. Often we do work in a certain way because we were told to do it that way, and sometimes never question why. Which brings me to my thought as to why many teach/preach not to mix voltage. They are typically refering to 120/208 in the same conduit with 277/480. I will not offer my opinion as to whether it's a good practice,
but I'm sure others will.
And that would be safety concerns. Which could probably lead to a whole new thread of discussion.

[This message has been edited by TE (edited 09-03-2002).]



Member Spotlight
BEAMEUP
BEAMEUP
WA
Posts: 27
Joined: December 2004
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: 0.016s Queries: 14 (0.003s) Memory: 0.7764 MB (Peak: 0.9238 MB) Zlib enabled. Server Time: 2017-03-25 01:54:34 UTC