ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Increasing demand factors in residential
by gfretwell - 03/28/24 12:43 AM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
Cordless Tools: The Obvious Question
by renosteinke - 03/14/24 08:05 PM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
1 members (CoolWill), 250 guests, and 13 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 2 of 2 1 2
Joined: Jul 2002
Posts: 680
W
Member
If the EE is a PE(professional Engineer) can't he sign off on the change and supercede code which would get your butt off the chopping block if something bad happens??

Stay up to Code with the Latest NEC:


>> 2023 NEC & Related Reference & Exam Prep
2023 NEC & Related Reference & Study Guides

Pass Your Exam the FIRST TIME with the Latest NEC & Exam Prep

>> 2020 NEC & Related Reference & Study Guides
 

Joined: Jan 2003
Posts: 4,391
I
Moderator
Quote
If the EE is a PE(professional Engineer) can't he sign off on the change and supercede code

No, an engineer can not change the adopted code.

What you may be thinking of is this.

Quote
310.15 Ampacities for Conductors Rated 0–2000 Volts.
(A) General.

(1) Tables or Engineering Supervision.

Ampacities for conductors shall be permitted to be determined by tables or under engineering supervision, as provided in 310.15(B) and (C).

Under engineering supervision ampacities may be different than the NEC tables.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Joined: Jul 2002
Posts: 680
W
Member
I thought an Engineer could sign off a change in an industrial or commercial setting??

Joined: Oct 2004
Posts: 265
D
dmattox Offline OP
Member
I understand what you are saying luckyshadow, but I have already appealed it to the engineer and he has said do it his way. At the end of the job I will have to sign the plans stating I did it per the plans. So I either need to keep confronting the EE, or lie about what I did on the job.

I am thinking about doing the 3/4" run + pulling a #6 ground in each 2". I'll be pushing the wire fill by 2 mm^2, but at least I'll know if there is a ground fault the breaker will trip. And I don't think its wrong for me to exceed what the plans call out.

My other option is to walk the inspector right by and have him issue a correction [Linked Image]

Joined: Jan 2005
Posts: 5,445
Likes: 2
Cat Servant
Member
Engineers have assumed an armload of "powers" over the years......but the last I checked, codes are laws, and the only 'party' that can 'supercede' a law is a jury.

Not that anything will slow down an engineer in his assumptions that he, and he alone, is all-knowing and all-wise. I once put my job on the line, when an engineer insisted it was OK to stand on the bumper of a crane, to provide additional counter-weight!

Joined: Sep 2003
Posts: 650
W
Member
Quoth George Little:
Quote

What Winnie is saying is only true when there is fault current involving the grounding conductor. Normally you wouldn't have any current flowing in the grounding conductor hence no magnetic field.

For my points 1 and 2 I agree with George above. The issues that I was describing would only occur when a fault current is flowing, and would act to change the impedance of the fault current path, and would also act to dissipate power in the conduit system. I should have stated this more clearly.

But for point 3, I am specifically pointing out that there is _always_ some noise current flowing in the conduit system, even without an electrical fault. This may be caused by things like ground coupled TVSS devices, ground referenced signaling devices, magnetic coupling to the conduit system, etc. The whole reason for an 'isolated' ground is to provide a _single_ path right back to the building ground reference, with no loops. By running the 'isolated' ground via a different path from the circuit conductors, you permit currents in the conduit system to transformer couple and induce voltages in the isolated ground, IMHO eliminating the benefit of the isolated ground in the first place.

I should add that this is conjecture on my part. I do not know the magnitude of the noise voltages on conduit in industrial settings, and I don't know how much current is actually flowing, so I don't know the magnitude of the transformer induced voltages that I'm describing. But running the isolated ground in a way that would pick up electrical noise seems as 'wrong' to me as spending extra money for an IG receptacle in a home wired with NM-B.

-Jon

Page 2 of 2 1 2

Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5