QOD for 04/11/2006

[gbeaumont (Gerry Beaumont)]

Hi to all,

why would anyone have an issue with a web page available in the public domain with both a save and print function on it??

Couresty ECN www.ecmweb.com

Find out why the National Electrical Code “25 ohms or less” rule may have less to do with power quality than you think.
Nearly all electricians and electrical inspectors are familiar with the National Electrical Code requirement in Sec. 250-54, which requires the resistance to ground of a single-made electrode (e.g., ground rod) to be 25 ohms or less. Unfortunately, it seems many electrical professionals don’t actually test the grounding electrode system (GES) to ensure they’re meeting this requirement. Even fewer of you feel testing the earth ground system is worthwhile. From a power quality perspective, you may be right.
A GES provides:
• A zero-volt reference for the supplied or derived power systems.
• A path to dissipate lightning or fault current (for higher voltage systems).
• A path for the dissipation of electrostatic currents.
A GES consists of two components: the grounding electrode conductor (GEC) and the grounding electrode.
You can choose a bare or insulated GEC (sized per Table 250-66) in copper or aluminum. The GEC connects the grounding electrode to the grounded circuit conductor, the equipment-grounding conductor, or both, at the main service equipment or the source of a separately derived system.
The most common types of grounding electrodes (identified by Sec. 250-50 and 250-52) are:
• Structural steel
• Metal underground water pipe
• Ground ring
• Ground rods
How to test. You should measure the resistance of an electrode with respect to the surrounding soil in the area. You can only do this by using the fall-of-potential method with a three-terminal, earth ground resistance tester. To properly test the resistance of a GES, you must follow some simple rules:
1. Disconnect the electrode under test from the rest of the electrical system. Considering this, it is not possible to test the grounding electrode system in nearly all circumstances.
2. Don’t use a meter that injects DC current into the ground rod. Do not use standard VOMs.
3. Don’t perform test measurements if the current on a GES is greater than 5A.
Contrary to popular belief, clamp-on earth ground resistance testers can be inaccurate in field applications. These testers require a low-resistance feedback loop with adequate spacing between electrode systems to provide meaningful readings. Many people often add a high resistance (caused by loose connections in the feedback loop) to the displayed value of the meter. Also, inadequate spacing between electrodes results in the meter only making a comparative bonding test, which almost always results in a low-resistance value.
Why do I need to reach 25 ohms? The most credible answer to this question is: 25 ohms is a reasonable value to strive for, given the average soil resistivity for most regions of the United States. Keep in mind, however, that 25 ohms is not a requirement when you install multiple electrodes. This is only a requirement for single-made electrodes, per Sec. 250-56. If you drive the first rod and get a resistance reading greater than 25 ohms, the NEC allows you to drive an additional rod 6 ft away from the first rod.
Let’s say, for example, you drive a ground rod into the soil, but instead of testing that rod to see if it meets the 25-ohm criteria you drive the second. Once the two rods bond together, consider the GES complete. But if you don’t take a measurement, how do you know your installation meets Code?
Reality check. In most commercial and industrial low-voltage power systems, technicians do not perform earth ground resistance testing. But this shouldn’t surprise you. An informal poll of 50 electricians found only four performed earth ground testing in the past. The reasons cited for not testing were:
• The testers were too expensive.
• The test was too confusing and took too much time.
• Two rods are good enough (most common response).
Impact of power quality. Believe it or not, nearly all electronic equipment will operate properly without the benefit of a low-resistance GES. Power quality site surveys have shown that in situations where the grounding electrode resistance is between 5 ohms and 105 ohms, it doesn’t affect equipment. However, you can trace most problems to poor quality connections on the equipment-grounding system. Therefore, you should pay less attention to the GES measurement and more to the impedance of the equipment-grounding system and the verification of low-resistance bonding connections between grounding planes.
What’s the lesson here? Spend less time on the testing and qualification of the GES resistance and more time checking the bonding between locations and the equipment-grounding conductor impedance.

Regards

Gerry

[pabernathy (Paul Abernathy, CMI®, CMECP® Electrical Code Academy,Inc.)]

EXACTLY…I tell you why…because BOOK NERDS know nothing about working electricity in the REAL WORLD so they complain and cry and whine to get posts removed…

I tell you…the NEXT post of mine that is removed because an old man does not like it…Can KISS my butt goodbye from helping NACHI at all…

[pabernathy (Paul Abernathy, CMI®, CMECP® Electrical Code Academy,Inc.)]

Amazing…Truly Amazing the level some will drop…

[rbennett (Richard L. Bennett, RETIRED)]

Paul

Some how I have lost the objective – I thought we were on the same page

Have I posted something that you think is out of line.? I agree that the building inspector is god and if he wants 3 ground rods hey lets pound them in. Where I am still thinking is on older homes and I am still thinking.

Gerrys posting about DC or AC testing of ground resistance or impedance is another subject.

My posting on another thread is more related to your own home as a weekend home owner trying to make your home a safe place to live

Install or repair your ground system

Hay if I said something wrong I am sorry – and if your can’t take the apologize then KMA$$

Do we understand each other??

I really would like to keep this to fact and not to emotion

Am I on the same page that you are on or should I be on a different thread???

BTW I thank your again to the test equipment link – I think is is better than a SURETEST

rlb

[pabernathy (Paul Abernathy, CMI®, CMECP® Electrical Code Academy,Inc.)]

lol…NOOOOOO…not you Richard…

I posted a interesting article for you…JUST for you and SOMEONE …I wont call names cried and complained to NACHI to have it removed because of copyright fears…BUT it was NOTHING to fear…hell anyone could download it…

lol…I dont want to kiss you A$$ fella…if I dont like something you say TRUST me I will tell ya…lol…had nothing to do with you…lol

[rbennett (Richard L. Bennett, RETIRED)]

10-4 Paul

Have a good day I understand

Thanks for the PM – It made my day

rlb

[pabernathy (Paul Abernathy, CMI®, CMECP® Electrical Code Academy,Inc.)]

What is scary…is even though HI’s dont test it…should know it when looking at the grounding system…and over 40% got this one wrong…OUCH…

Ok…guys come to OHIO…thehehehehe…WE gonna learn some stuff…and Git Er Done…

[jtedesco1 (Joe Tedesco)]

AEMC
Ground resistance Earth testers
www.omnicontrols.comMegabras
High-end megohmmeters at affordable prices. Up to 20kV test voltages.
www.megabras.comGrounding Systems
CADWELD grounding materials, ERITECH ground rods, accessories
www.erico.com

[jtedesco1 (Joe Tedesco)]

Hey Paul

Who complained? Probably was someone from Arizona or California?

I post most of my articles from EC&M and no one has a problem with that so far why here are a few:

NACHI electrical trainer’s latest articles.

NACHI electrical trainer Joe Tedesco has written some great articles. Enjoy:

http://www.nachi.org/documents/304ecm15.pdf
http://www.nachi.org/documents/305ecm15.pdf
http://www.nachi.org/documents/305ecm30.pdf
http://www.nachi.org/documents/306ecm15.pdf
http://www.nachi.org/documents/306ecm30.pdf
http://www.nachi.org/documents/308ecm15.pdf
http://www.nachi.org/documents/308ecm30.pdf
http://www.nachi.org/tenguidelines.htm

About NACHI’s Joe Tedesco.

Thanks Joe!

[tgardner (Timothy Gardner, VA HI Lic# 3380000992 NRS)]

Paul,

I sometimes answer wrong to see if I can suck someone in that views the poll before voting. OOOPS, did I say that?

tg

[jtedesco1 (Joe Tedesco)]

http://re2.mm-so.yimg.com/image/1700930923
TheStrike.rm 352x240 - 0:04 - 335.9kB www.marinelightning.com/FA…

[pabernathy (Paul Abernathy, CMI®, CMECP® Electrical Code Academy,Inc.)]

Tim,

lol…leave it to a Virginia Guy to do that…lol

[tgardner (Timothy Gardner, VA HI Lic# 3380000992 NRS)]

—old indian trick—

tg

[pabernathy (Paul Abernathy, CMI®, CMECP® Electrical Code Academy,Inc.)]

I hear ya Kemo Sabi…heck I cant spell tanto language