CLICK HERE AND JOIN OUR COMMUNITY TODAY, IT'S FREE!
Go Back   Electrician Talk - Professional Electrical Contractors Forum > Electrical Trade Topics > NEC Code Forum

Reply
 
Thread Tools Search this Thread Display Modes
Old 06-26-2008, 07:19 PM   #1
Junior Member
 
Join Date: Jun 2008
Location: Texas
Posts: 9
Rewards Points: 10
Default Ground Rod Resistance

It's been a while since I have done any grounding. What is the maximum resistance between the ground rod and earth?

Billy716 is offline   Reply With Quote
Join Contractor Talk

Join the #1 Electrician Forum Today - It's Totally Free!

ElectricianTalk.com - Are you a Professional Electrical Contractor? If so we invite you to join our community and see what it has to offer. Our site is specifically designed for you and it's the leading place for electricians to meet online. No homeowners asking DIY questions. Just fellow tradesmen who enjoy talking about their business, their trade, and anything else that comes up. No matter what your specialty is you'll find that ElectricianTalk.com is a great community to join. Best of all it's totally free!

Join ElectricianTalk.com - Click Here JOIN FOR FREE


Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. ElectricianTalk.com DOES NOT guarantee the accuracy or completeness of any information contained on this site. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!

Old 06-26-2008, 07:31 PM   #2
Moderator
 
Speedy Petey's Avatar
 
Join Date: Jan 2007
Location: NY State
Posts: 9,059
Rewards Points: 2,026
Default

250.56 Resistance of Rod, Pipe, and Plate Electrodes
A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode of any of the types specified by 250.52(A)(2) through (A)(7). Where multiple rod, pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.

Speedy Petey is online now   Reply With Quote
Old 06-26-2008, 07:33 PM   #3
Senior Member
 
brian john's Avatar
 
Join Date: Mar 2007
Location: Leesburg, VA
Posts: 25,141
Rewards Points: 2,000
Default

One rod 25 ohms drive two rods and anything you get or don't get, because there is no requirement to measure the resistance.
brian john is offline   Reply With Quote
Old 06-26-2008, 07:41 PM   #4
Electrical Contractor
 
wirenut1110's Avatar
 
Join Date: Feb 2008
Location: Chester, VA./
Posts: 253
Rewards Points: 250
Default

As Brian said, just drive 2 then there's no question, except what $10?
__________________
Jim
wirenut1110 is offline   Reply With Quote
Old 06-26-2008, 07:43 PM   #5
Junior Member
 
Join Date: Jun 2008
Location: Texas
Posts: 9
Rewards Points: 10
Default

What we've got is a very sandy desert area and are having a hard time getting a good ground.
Billy716 is offline   Reply With Quote
Old 06-26-2008, 07:45 PM   #6
Electrical Contractor
 
wirenut1110's Avatar
 
Join Date: Feb 2008
Location: Chester, VA./
Posts: 253
Rewards Points: 250
Default

how are you determining "not a good ground"?
__________________
Jim
wirenut1110 is offline   Reply With Quote
Old 06-26-2008, 07:48 PM   #7
Junior Member
 
Join Date: Jun 2008
Location: Texas
Posts: 9
Rewards Points: 10
Default

There's no difference of potential from the hot to the rod. We are already down two sections of rod.
Billy716 is offline   Reply With Quote
Old 06-26-2008, 07:55 PM   #8
Senior Member
 
brian john's Avatar
 
Join Date: Mar 2007
Location: Leesburg, VA
Posts: 25,141
Rewards Points: 2,000
Default

That is not how you measure ground resistance and most likely means little to nothing.

Second who is requiring this?

What if anything is the spec?
brian john is offline   Reply With Quote
Old 06-26-2008, 08:04 PM   #9
Junior Member
 
Join Date: Jun 2008
Location: Texas
Posts: 9
Rewards Points: 10
Default

I'm stuck in Iraq. I don't have the right equipment. I don't have a good ground and I am trying to get one. The sand here is unbelievable and goes down forever.
Billy716 is offline   Reply With Quote
Old 06-26-2008, 08:09 PM   #10
Senior Member
 
brian john's Avatar
 
Join Date: Mar 2007
Location: Leesburg, VA
Posts: 25,141
Rewards Points: 2,000
Default

WHY WHY WHY.......WHY..


What is the requirement requiring this GOOD GROUND WHY.

I am not being sarcastic I am SERIOUSLY trying to understand why. What is driving this?
brian john is offline   Reply With Quote
Old 06-26-2008, 08:12 PM   #11
Junior Member
 
Join Date: Jun 2008
Location: Texas
Posts: 9
Rewards Points: 10
Default

I'm frustrated. We've had at least 12 soldiers die of electrocution due to poor grounding. The pressure is on us to make sure we have it and rightfully so. We are having a hard time getting it and I am looking for some suggestions.
Billy716 is offline   Reply With Quote
Old 06-26-2008, 08:17 PM   #12
Senior Member
 
brian john's Avatar
 
Join Date: Mar 2007
Location: Leesburg, VA
Posts: 25,141
Rewards Points: 2,000
Default

In our industry there is this driving need to have a low resistance to earth. In the realm of all electrical requirements for safety this ranks at the bottom of the list.

Are there times where a low earth resistance is necessary YES, but seldom is this the case in a typical electrical installation, Good bonding YES, Low resistance grounding utilizing ECG's between equipment yes. But driving a rod into the earth. WHY?
brian john is offline   Reply With Quote
Old 06-26-2008, 08:19 PM   #13
Moderator
 
Speedy Petey's Avatar
 
Join Date: Jan 2007
Location: NY State
Posts: 9,059
Rewards Points: 2,026
Default

Driving a ground rod will NOT(!) cure an electrocution problem!

I can't believe there are no engineers (or whatever) there that know this.
Speedy Petey is online now   Reply With Quote
Old 06-26-2008, 08:22 PM   #14
Senior Member
 
brian john's Avatar
 
Join Date: Mar 2007
Location: Leesburg, VA
Posts: 25,141
Rewards Points: 2,000
Default

NO you did not, you has 12 electricians die from poor electrical wiring and poor BONDING of all metallic parts. Earth has nothing to do with this and until you (those involved in this not necessarily you) understand this some will continue to be hurt.

Hell if the earth is that lousy of a conductor, it is actually safer you can hold a ungrounded/hot/energized conductor and stand bare naked on the earth SAFELY.

SCREW THE GD EARTH... install proper wiring with proper grounding (BONDING) of all metallic parts.
brian john is offline   Reply With Quote
Old 06-26-2008, 08:23 PM   #15
Town Drunk
 
JohnJ0906's Avatar
 
Join Date: Jan 2007
Location: Baltimore, MD, USA
Posts: 3,722
Rewards Points: 2,000
Default

Quote:
Originally Posted by Billy716 View Post
I'm frustrated. We've had at least 12 soldiers die of electrocution due to poor grounding. The pressure is on us to make sure we have it and rightfully so. We are having a hard time getting it and I am looking for some suggestions.
They did not die from poor grounding. They died from poor bonding.

What will a stick in the earth do to prevent these deaths?
__________________
John from Baltimore
"One day at a Time"
All responses based on the '08 NEC
It's not my fault, it's not my problem, I'm not your solution.
JohnJ0906 is offline   Reply With Quote
Old 06-26-2008, 08:24 PM   #16
Member
 
Join Date: Jul 2007
Location: Connecticut
Posts: 84
Rewards Points: 75
Default

Quote:
Originally Posted by Billy716 View Post
I'm stuck in Iraq. I don't have the right equipment. I don't have a good ground and I am trying to get one. The sand here is unbelievable and goes down forever.
What makes a good ground? if you dont have the right equipment, how do you know you have a bad ground? FWIW, it has nothing to do with clearing a fault and tripping the OCD...
Stickboy1375 is offline   Reply With Quote
Old 06-26-2008, 08:27 PM   #17
Senior Member
 
cmec's Avatar
 
Join Date: Feb 2008
Posts: 228
Rewards Points: 150
Default

I have dug around rods & put a piece of terra cotta tile or pvc up on end fill it with rock salt and water it then take a reading drops the resistance real quick in normal soil,If you dont have any enviromentalist /tree huggers copper sulfate works good. dont know what chemical to use for sand?

They sell rods that are hollow you can put chemicals in .

Last edited by cmec; 06-26-2008 at 08:33 PM.
cmec is offline   Reply With Quote
Old 06-26-2008, 08:29 PM   #18
Member
 
Join Date: Jul 2007
Location: Connecticut
Posts: 84
Rewards Points: 75
Default

Quote:
Originally Posted by cmec View Post
I have dug around rods & put a piece of terra cotta tile or pvc up on end fill it with rock salt and water it then take a reading drops the resistance real quick in normal soil,If you dont have any enviromentalist /tree huggers copper sulfate works good. dont know what chemical to use for sand?

Is lightning a huge threat in the desert?
Stickboy1375 is offline   Reply With Quote
Old 06-26-2008, 08:34 PM   #19
Senior Member
 
brian john's Avatar
 
Join Date: Mar 2007
Location: Leesburg, VA
Posts: 25,141
Rewards Points: 2,000
Default

CMEC:

There are a variety of methods for lowering ground resistance, do a web search, DEEP EARTH GROUNDING, XIT, hell if I thought it would help I'd GIVE a 3-point tester, pay the shipping and give an online tutorial to billy716, BUT this is not the problem, not the issue, not the solution.

I want him and all our soldiers and contractors to be safe. There are ways to make this happen but peeing on a stick in the earth ain't he solution.
brian john is offline   Reply With Quote
Old 06-26-2008, 08:41 PM   #20
Wyome
 
Join Date: Jun 2007
Location: WY
Posts: 558
Rewards Points: 518
Default

I've read about this. Soldiers dying in the showers. I wondered at the time what was wrong, but it sounds as if it is more than just inadequate ground. I am guessing you use generator power over there. Whatever is causing this might be coming from energized piping and a good earth ground in the same area. Electric water heaters? Maybe you don't need water heaters in Iraq. If you have an overhead distribution system with a common grounding point that is tied to neut, then maybe that bond has failed. For all I know, you don't even use 2 hots and a neutral like we do in the states.
Measure across various pipes to drains or metal dividers until you find where the voltage is. Then shut down all power to your site and measure again. If the voltage is gone then turn on circuits one by one until it appears again. Then troubleshoot that circuit. If the voltage does not go away, then suspect your nearest neighbors. Check for solid neutral connections at neighbor's panels. You can even get voltage from phone wires that are damaged and lying on anything conductive. eg. metal pipes. roofing, metal walls. I don't know if phone voltage is enough to kill a person though.
This situation is tragic. You guys over there have enough to worry about without having to think about checking out in a shower where you should be safe.
Good luck and may God bless all of you.

te12co2w is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Ohms(resistance) Testing wallace7777 Services and Service Equipment 19 11-23-2008 02:54 PM
loop resistance & capacitance voltage transformers speedtronic General Electrical Discussion 2 10-30-2008 05:02 AM
loop resistance of generator/transformer winding speedtronic General Electrical Discussion 8 08-26-2008 10:21 PM
Ever have a fuse with an abnormal resistance? MNservicetech General Electrical Discussion 7 08-09-2008 01:21 PM
Measuring of generator winding resistance m.s.j General Electrical Discussion 4 07-10-2007 03:12 PM


All times are GMT -4. The time now is 03:46 PM.


Copyright 2006-2014 Escalate Media LP. All Rights Reserved
Our Pro Sites Network
ContractorTalk.com | DrywallTalk.com | HVACSite.com | PaintTalk.com | PlumbingZone.com | RoofingTalk.com