Allowable current on house ground?

[SSASNT3]

As the title states, is there a code mention on the max current allowable on a home's ground?

We are using a ground clamp meter to monitor, and the max allowable for the clamp's accuracy is 5... understood that this is not per code but per manufacturer. It also states in the manufacturer's manual that amperage on the ground should be less than 2 if under 20 ohms and under 400mA if over 20ohms resistance, but no mention as to where this comes from.

THanks in advance!

 

[charlie b]

There should never be any current on a home's ground. Let me ask how this question pertains to your employment in the thermal imaging business.

 

[SSASNT3]

It doesn't apply to my thermal imaging experience. A friend asked and I knew that the Mike Holt forum would be the best place to find a code related question.


Thank you for the response. I realize that current on the ground is indicative of a bigger issue, but is there some minor amount allowable? Possibly harmonics related?

 

[curt swartz]

Welcome to the forum!

Can you please provide more info? What is a ground clamp meter? Where are you measuring this current?

 

[don_resqcapt19]

Assuming that we are talking about the grounding electrode conductor, there will always be current on if if there is current on the grounded conductor. The amount of current will depend on the impedance of path back to the source via the grounding electrode. In the case of a common metal underground water piping system being used as the grounding electrode, it would not be uncommon to fine 20% or more of the grounded conductor current on the GEC that connected to the water pipe.

 

[SSASNT3]

Welcome to the forum!

Can you please provide more info? What is a ground clamp meter? Where are you measuring this current?

It is an IDEAL 61-920 Ground Resistance Clamp meter. Needs a "closed loop" ground to operate. It is measured on the ground conductor leading to the ground rod or ground on the city water.

 

[al hildenbrand]

. . . is there a code mention on the max current allowable on a home's ground?

Directly answered: No.

I disagree with Charlie as to whether there "should be" current, and agree with Don.

Now, in your question, the term "a home's ground" is not specific enough to be understood here, as there are a selection of different "grounds" that are put together to make up a home's "Grounding Electrode System" (GES). Metallic water supply piping, structural steel, concrete encased electrode, ground ring and / or plate, "made" electrodes such as ground rods, etc., are examples of what your term "a home's ground" may include. Hence the reason Curt is asking for further information.

The normal cause of measureable current in the GES is, in a phrase, the unbalance current of the home's running load, any additional unbalance current at the local power company transformer secondary coming from the home's neighbors, as well as currents coming off the power distribution grid that find a parallel return path in the "home's ground" to other sources.

 

[SSASNT3]

Directly answered: No.

I disagree with Charlie as to whether there "should be" current, and agree with Don.

Now, in your question, the term "a home's ground" is not specific enough to be understood here, as there are a selection of different "grounds" that are put together to make up a home's "Grounding Electrode System" (GES). Metallic water supply piping, structural steel, concrete encased electrode, ground ring and / or plate, "made" electrodes such as ground rods, etc., are examples of what your term "a home's ground" may include. Hence the reason Curt is asking for further information.

The normal cause of measureable current in the GES is, in a phrase, the unbalance current of the home's running load, any additional unbalance current at the local power company transformer secondary coming from the home's neighbors, as well as currents coming off the power distribution grid that find a parallel return path in the "home's ground" to other sources.

Many thanks! Great info, and thanks to Don as well. I've got my answer and I owe it all to the good folks of this forum.

 

[infinity]

I've checked the GEC at the water pipe in my house and it typically has a few amps on it. Normal if you have a city water system where multiple houses are connected together.