ground and bond testing

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helena

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Are company has been asked to start a grounding and bonding test program to document that all are services and equipment are properly grounded and bonded. I am looking for some help in what direction I need to go to start such a program and if there is any document ion out there to work with.
 
Re: ground and bond testing

The simple answer is to start with Art 250 of the NEC.
The real question is what is the reason for the test? the nature of the equipment will dictate the expense involved in testing. For example, at a submarine base near hear, the bomb bunkers have a lightning protection system that is tested every month.
 
Re: ground and bond testing

First you need to define what the test are. I would take a look at IEEE Emerald & Green Book.

[ October 11, 2004, 03:05 PM: Message edited by: dereckbc ]
 
Re: ground and bond testing

You should find this page of the InterNational Electrical Testing Association (NETA) useful.

Its been a while since I've used it, so my copy of NFPA 70B is a bit out of date, but it and NETA's own Maintenance Testing Specification should cover your need. They address Tom and Dereck's replys fairly well too.
 
Re: ground and bond testing

Hello-

Like the others, I'm curious as to who is asking you to start this program.

I suspect that you are looking for something that OSHA calls the "Assured Equipment Grounding Conductor Program", where the construction industry performs routine electrical testing on equipment, hand tools, and grounding systems at the job site. You can find out more information at www.osha.gov under their electrical section or just do a google search.

If this is not what you are looking for, you might try talking your boss out of having to start such a program- unless he or she is willing to invest in the correct equipment and do the job right.

I've seen too many electrical contractors try to get involved in the electrical testing business, but they try to do it on the cheap.

A quality 3-point fall of potential tester, used to measure the earthing portion of a buildings grounding system, runs about $3,000. A ground impedance tester, used to check the equipment grounding conductor and bonding side of a buildings grounding system, can cost up to $6,000.

These instruments also require routine calibration, which is about $500 annually for the pair.

What I typically see are companies using a $300 dollar "Sure-Test" wiring analyzer and a $1200 AMEC clamp-on resistance tester to do this job. These are fine tools when used properly and according to manufacturers instructions, but I wouldn't stake my companies reputation on them as it is too easy to get an incorrect reading.

Good luck,

Mark
 
Re: ground and bond testing

Thank-you for the additional information in the private message.

Even though you do not fall under the OSHA Construction standards, the Assured Equipment Grounding Conductor Program (AEGCP) should meet the requirements for your grounding and bonding testing program. Under normal circumstances, OSHA gives you the choice between installing GFCIs or conducting grounding testing. In this case, because of the nature of your work, you'll want to conduct the testing rather than putting a GFCI on everything.

The big plus is that the Sure-Test brand wiring tester is ideal for this application since you won't need highly accurate readings.

Also, you will want to get a copy of NFPA Standard 77, Recommended Practice on Static Electricity. Appendix C describes all the correct bonding methods needed for your application and Section 5.8 describes the assessment of the static grounding and bonding system.

Good luck,

Mark
 
Is anyone aware of an inexpensive electrical test instrument that could be used in compliance with the AEGCP [Assured Equipment Grounding Conductor Program]. I'm looking for a simply pass/fail device for bench testing electrical handtools and extension cords. Thanks
 
We normally test hundreds of cords and tools every quarter to conform to OSHA and NEC requirements for an assured grounding program. The cords are identified by color coded tape to indicate they have been tested and a log is kept of electrically powered hand tools for any inspector wanting to inspect our procedures. All tools are identified with a number and that is kept in the log with the date of inspection. The only requirement I have ever seen questioned was the qualifications of the person inspecting the tools. We will normally have a licensed electrician doing the testing.

We do the following tests:
a.. visually inspect the cords for any visible damage.
b.. visually inspect the cord ends for broken or damaged prongs.
c.. visually inspect tools and cords for any abnormality.
d.. Testing of tools is done using any analog ohm meter.
1.. Test from hot to neutral prong of cord end. Reading should be "0"
2.. Test from hot to grounding prong. Reading should be infinity.
3.. Test from neutral to grounding prong. Reading should be infinity.
e.. After completion of (d) plug tool into a GFCI receptacle and see if it
works OK without tripping anything.
f.. If all is well we document the test in the log and install the color coded
tape on the tools cord.
g.. Testing cords is easier than testing tools. Install a GFCI receptacle for
testing cords.
1.. Plug cord into GFCI. If receptacle doesn't trip, so far so good.
2.. We use a receptacle testing device, normally bought at Lowe's or
Home Depot for about $5.00 or less.
a.. With cord plugged into GFCI, plug device in cord and see if all is
well. Different combinations of lights display results.
b.. If OK, we change the color code tape and make available to field.

Hope this helps
 
The '02 NEC 250.56 requires a ground rod to have a resistance of 25ohms or less (or augmented with one additional electrode...). Is it permissable to verify this with your own ground resistance tester? Which type of instrument can be used? Does it need to be a 3rd party? I realize that the answers will vary from place to place; I'm just curious what experience others have had with this subject. Driving a 2nd rod is usually cheaper than testing but if a particular area has consistantly low resistance soil conditions, alot of time, effort and money can be saved in the long run by prooving it. Thoughts??
 
Bob, Marks post should have answered your question, typically a 3 point fall of potential test runs a couple hundred bucks, and should be done every 3 years.

Tom, you must be near Bangor, and therfore must know what a Bremalope is :)
 
The NEC doesn't seem to require periodic testing to insure that the rod stays under 25ohms. In fact the NEC doesn't seem to care how much resistance is there at all if you have 2 rods spaced 1.8 meters apart. I would think, based on how nonchalant the NEC is about multiple rods, that using an inexpensive ($1200) clamp on resistance tester should be just fine.
 
bkludecke said:
The NEC doesn't seem to require periodic testing to insure that the rod stays under 25ohms. In fact the NEC doesn't seem to care how much resistance is there at all if you have 2 rods spaced 1.8 meters apart. I would think, based on how nonchalant the NEC is about multiple rods, that using an inexpensive ($1200) clamp on resistance tester should be just fine.
Click to expand...

Why waste time and money with a test at all? As long as the installation has incurred no damage and there are no changes that might affect things (like new water pipes being run) I'd be inclined to just do a physical damage survey and be done with it.
 
The reason I would test is to avoid installing the 2nd rod. Our area is quite rocky and driving rods (even with a jackhammer) is often a challenge. If a simple clamp-on grd resistance tester will do the trick it would be well worth the $$. I'm going to ask our AHJ if they will accept such a test and if so I will rent one & try it on a few locations. If I get less than 25 ohms then I'll buy one. I was just wondering what other jurisdictions do.
 
"The '02 NEC 250.56 requires a ground rod to have a resistance of 25ohms or less (or augmented with one additional electrode...). Is it permissable to verify this with your own ground resistance tester? Which type of instrument can be used?"

I have had occasion to think about this after a recent discussion with an electrical inspector. You can do it with what is in your toolbox.

1. Connect a 120 volt line to the new ground rod (not yet connected to the system) through a limiting resistor such as a light bulb.

2. Measure the current with clamp-on ammeter; probably on the order of one amp, depending on light bulb Watts.

3. Measure voltage relative to earth at the conductor going to ground rod. You don't need a very good ground to earth for the meter because the voltmeter draws very little current.

4. Divide Volt by Amps to get Ohms.

I recommend that you use an insulated conductor for the test and stand at least ten feet away from the ground rod while it's hot.

It helps to put salt water in a hole in the ground near the rod a few days before the measurement.
 
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How do you verify you are out of the sphere of infulence with this test? What distances are you using for this test?

"It helps to put salt water in a hole in the ground near the rod a few days before the measurement." - OK, that will help you get a good reading, but not a true reading, if you are doing this to influence your test results to get a better reading, why test at all?

IMO, this is dangerous and inaccurate advice and this post should be removed by the moderator.
 
zog said:
How do you verify you are out of the sphere of infulence with this test? What distances are you using for this test?

"It helps to put salt water in a hole in the ground near the rod a few days before the measurement." - OK, that will help you get a good reading, but not a true reading, if you are doing this to influence your test results to get a better reading, why test at all?

IMO, this is dangerous and inaccurate advice and this post should be removed by the moderator.
Click to expand...

I agree with the "why test at all" philosophy. If it is acceptable to have 5000 ohms with two rods, there is no need to test at all. Just drive two rods.

I don't see how dumping salt water around the rod will change your reading all that much. I also don't see it as an especially dangerous practice, since the ground rod really serves as little more than a placebo to begin with.
 
The salt water idea really would give you a false measure, since it will be washed away by rain in the future. Salt water does make a difference. I measured 10 amps on a ground rod that pierced a salt water table near an estuary.

A light bulb has variable resistance depending whether it is cold or fully incandescent. I did a similar test without a line resistor since I knew the rod/earth resistance would be high enough. With a clamp on I just got milliamps. But it would be a way to simply calculate the resistance, no?

Since it is so simple and inexpensive I wonder if there is something I am overlooking.

Karl
 
Bob NH said:
"The '02 NEC 250.56 requires a ground rod to have a resistance of 25ohms or less (or augmented with one additional electrode...). Is it permissable to verify this with your own ground resistance tester? Which type of instrument can be used?"

I have had occasion to think about this after a recent discussion with an electrical inspector. You can do it with what is in your toolbox.

1. Connect a 120 volt line to the new ground rod (not yet connected to the system) through a limiting resistor such as a light bulb.

2. Measure the current with clamp-on ammeter; probably on the order of one amp, depending on light bulb Watts.

3. Measure voltage relative to earth at the conductor going to ground rod. You don't need a very good ground to earth for the meter because the voltmeter draws very little current.

4. Divide Volt by Amps to get Ohms.

I recommend that you use an insulated conductor for the test and stand at least ten feet away from the ground rod while it's hot.

It helps to put salt water in a hole in the ground near the rod a few days before the measurement.
Click to expand...

Where is the deduction in this method for the resistance of the light bulb in the circuit? That value should be a factor in the equation.
 
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