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
0 members (), 263 guests, and 17 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 3 of 3 1 2 3
#96878 01/05/06 02:15 PM
Joined: Oct 2004
Posts: 135
B
Member
The human body has roughly 25 ohm's of resistance and heart beat pulses at 60hz. So the path to ground needs to be less, so current choose's the least resistant path to ground: quote

I hope you're not being serious here, this is a gross misunderstanding of the concept of bonding and grounding. There is no way the human body has 25 ohms of resistance as this varies greatly between individuals and I would seriously doubt anyone would have a resistance that low. Sorry to be so blunt but what did you expect posting info. like that on a electrical forum?

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
 

#96879 01/06/06 01:39 PM
Joined: Aug 2003
Posts: 1,374
R
Moderator
The generator frame is bonded to the equipment grounding conductor, which will definatley have a resistance of less than 25 ohms. [Linked Image]


Ryan Jackson,
Salt Lake City
#96880 01/06/06 01:43 PM
Joined: Jun 2002
Posts: 58
E
Member
From the comments, I think I'm missing something. When I read the post and saw the image, I thought: SO, this is pretty standard, and is a standard requirement whenever I inspect generators for the circus, movie shoots, car dealer tent sales, etc. I'll at least see a ground rod, maybe two if we're in sand (within a mile of the ocean). Or, generator is connected to an existing grounding electrode system.
NEC art. 250-30 and 250-34 cover the grounding system pretty well: If you don't meet the exceptions in 250-34(a) or (b), then you're a separately-derived system under 250-30, your grounding system is just about like a building.
What have I missed?

#96881 01/07/06 06:58 AM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline OP
Moderator
skipr Has decided his wisdom is not needed here.

I removed his 'resignation' post.

skipr, you are welcome back here any time.

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#96882 01/07/06 07:08 AM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline OP
Moderator
energy7

Quote
From the comments, I think I'm missing something.

Perhaps.

I do not think any of us disputes that the NEC sometimes requires grounding electrodes for generators.

The reason the sticker caught my eye was that it specified 25 ohms or less.

If that label is part of the generators listing and labeling than 110.3(B) becomes a factor.

It may be imposable to achieve less than 25 ohms to ground.

Picture your generator at the circus, what do they do, install one or two ground rods?

Have you ever tested them to see if they had 25 ohms or less?

And then we get into the need for 25 ohms at all.

Why 25, what will that do for us.

The generators we installed where portable generators entirely cord and plug connected.

The generators themselves where not bonded as they where tied into bonded switch gear.

In this case the generators frame was grounded by the EGC we ran from the switchgear with the feeders.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#96883 01/07/06 08:08 AM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline OP
Moderator
To encourage further discussion where is the requirement that states a circus generator needs an electrode?


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#96884 01/07/06 01:46 PM
Joined: Jul 2004
Posts: 9,923
Likes: 32
G
Member
Careful Bob. You are going to start the "is a floating neutral safer than a bonded one" argument.
Some portable generators do not bond the neutral (like Honda) while most others do.
I know our lab supplies and convenience outlets in IBM machines used an isolation transformer that effectively lifted the neutral/ground bond.
It prevented ground loops when you used a scope but it was also supposed to be a safety thing.


Greg Fretwell
Page 3 of 3 1 2 3

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