measure resistance of grounding system

[KIRKBRO]

I am installing tvss and need to check my grounding system in a dairy.Tohave this done is quite expensive. Fluke has a meter (1630). Have heard good and bad about its reliablity the meter is also costly does anyone have any experence with this meter

 

[George Stolz]

What does a TVSS have to do with a grounding electrode system?

 

[mdshunk]

What does a TVSS have to do with a grounding electrode system?

It needs a place to shunt the current.

 

[George Stolz]

As I understand it, TVSS's generally do not shunt to earth, but from L-N or L-L.

I offer up this post, I am not an expert on this issue.

 

[dereckbc]

It needs a place to shunt the current.

It doesn't shunt to earth unless it is a direct strike to the building (rare). In which case any conductor appears as extremely high resistance and the GES impedance is of no importance.

Let's say you have that mythical 5 ohms or less GES, and a 10-foot long 750 MCM GEC installed to the disconnect. The 750 cable impedance alone at lightniong is greater then 3K-Ohm's in series with 5 which still equals 3K. What value does the GES bring to the table? I say it doesn't make a bit of difference.

In this scenerio if the service is properly configure, the N-G bond point will simple rise and fall at the point of the bond in reference to earth, but the equipment sees very little difference in normal operating voltages. That is the beauty of Single Point grounding if done properly.

 

[George Stolz]

Were your ears burning or something? :-?

 

[dereckbc]

No, just stumbled on to it!

 

[tom baker]

It needs a place to shunt the current.

Its a common misconception and I used to think that a "good ground" was required. As proof that a TVSS at the service does not require a ground, Art 285 TVSS was added to the 2002 NEC, and in the 2005 NEC, the provision was added for TVSS on ungrounded electrical systems.

 

[brian john]

Back to his statement, If testing is required in the specifications, than it is best to sub this out. It takes a bit more than just a meter to determine ground resistance. There are some clamp-ons available that do simplify matters but still take some understanding of their use. Unless you see a future in testing I suggest you sub it...

 

[coulter]

...Fluke has a meter (1630). ...does anyone have any experience with this meter

kirkbro -
You're sure not getting any answers to your specific question.

uhh .. Girls and Guys - He asked if anyone had any experience with a Fluke 1630. Does anyone?

 

[brian john]

I believe I answered his question in a round about way. The Fluke 1630 is a clamp on tester I own several clamp-ons Fluke and AEMC. Not overly impressed with them, but they do have their applications. If you are not going to do a fair amount of testing, then IMO your better off hiring a contractor familiar with the process.

But if you have a use for ground testing on a regular basis this is not the meter I would spend my money on. I would look at the AVO that incorporates a 3 point tester with a clamp-on.

 

[George Stolz]

kirkbro -
You're sure not getting any answers to your specific question.

uhh .. Girls and Guys - He asked if anyone had any experience with a Fluke 1630. Does anyone?

Carl, thanks for that. My apologies to Kirkbro for diverting his thread.

No, I don't have any ground resistance testing equipment.

 

[Pierre C Belarge]

The clamp-on meters are not for testing ground resistance, they test the individual ground electrode.

To test for ground resistance, you will need one of the "Fall of potential" type meters.

 

[dereckbc]

The clamp-on meters are not for testing ground resistance, they test the individual ground electrode.

Pierre IMO that is not exactly true, you can measure the GES if one knows exactly where to insert the loop tester. As mentioned though it does take some knowledge where to place the meter as not to read loops or an individual electrode.

I have used and own both loop testers and 3-point fall of potential. The 3-points are indeed more accurate, but require even more skill to operate not to mention much more time consuming.

The clamp on testers IMO are only good for checking specifications. For example is the spec says must be below 10-ohm's and the meter reads 9, you are OK, but the actual resistance will always be lower than the meter reads dues to the series nature of the meter.

 

[Pierre C Belarge]

My understanding of the clamp-on meters is that they are approximately 8% low on the readings.

I own a clamp-on.
I am curious as to how they can be used (if somewhat inaccurately) to measure the "ground/soil" resistance.
Would you by any chance have a link to some site for this info?

 

[dereckbc]

Pierre I will look for a link later when I get time. The instruction book lines out what I am saying so you might check AEMC website and see if they have an instruction book on-line.

Here is the skinny. The best place to use the meter is to clamp the grounded service conductor coming from the transformer. So what your are reading is the impedance of your ground electrode in series with the MGN of the utility.

 

[brian john]

http://www.aemc.com/techinfo/index.asp

 

[KIRKBRO]

Thanks for all the replys. I called the manufacture there reply was the better the grounding system the better , of course. My objective was to provide the cleanest power possible for the cost, dairies have more and more electronics every year latest is VFD 15-20 HP THE TVSS i PURCHASED SHOULD CLAMP TO 800V IF my understanding is correct,anything above that goes to ground thus my orignal question to test thanks agin this is my first trip to this site.

 

[KIRKBRO]

thanks for all the replys,I contacted the manufacturer they replyed the 25ohm was a code requirement and there equipment would operate properly with a service code accepted instalation.Dairies are requiring more & more electronics my objective was to provide my customer with the cleanest power possible for the cost. My understanding is the TVSS will clamp @ 800v removing spikes and surges to ground. Latest euuipment installed VFD 15-20HP. this is my first trip to the sight,thanks agin kirk

 

[George Stolz]

thanks for all the replys,I contacted the manufacturer they replyed the 25ohm was a code requirement and there equipment would operate properly with a service code accepted instalation.

They are misstating the grounding requirements of the NEC. A code compliant Grounding Electrode System can be thousands of ohms. Click here to see the 25 ohm requirement.