The ground is not "The Ground" and the pathology of NEC code.

[McKravitts]

Confused, confounded and puzzled are terms found throughout this forum about NEC code regarding “grounding”.

We are conditioned to believe that there is object; “the ground” that is electrically quiet, safe and always zero volts and could never be a party to harming anyone or damaging our equipment.

The authors of NEC code certainly want us to believe that, but their frequent updating, changing and sometimes seemingly contradictory requirements can only lead one to wonder if is there more to the ground than they care to share.

The ground is zero volts right! But relative to what? The ground.

If you had very long meter leads and placed one on your ground rod and the other on someone’s a mile away would your meter read zero?



I am starting this discussion in hope of clearing up some of the mystery regarding grounding and possibly help people develop grounding systems that meet code and protect their equipment as best as possible.

 

[Starex]

Confused, confounded and puzzled are terms found throughout this forum about NEC code regarding “grounding”.

We are conditioned to believe that there is object; “the ground” that is electrically quiet, safe and always zero volts and could never be a party to harming anyone or damaging our equipment.

The authors of NEC code certainly want us to believe that, but their frequent updating, changing and sometimes seemingly contradictory requirements can only lead one to wonder if is there more to the ground than they care to share.

The ground is zero volts right! But relative to what? The ground.

If you had very long meter leads and placed one on your ground rod and the other on someone’s a mile away would your meter read zero?



I am starting this discussion in hope of clearing up some of the mystery regarding grounding and possibly help people develop grounding systems that meet code and protect their equipment as best as possible.

The meter would likely not read zero volts and if you measure the voltage difference between your rod and your neighbors you could very well read something other than zero.
During lightning storms the reading could be in the 1000’s of volt range.

 

[McKravitts]

Would either neighbor have suffer any damage to any houshold electronics?

 

[Starex]

If both houses are properly wired (to code), there would most likey be no damage to either.

 

[McKravitts]

If one had 10,000 volts at their ground rod and that ground was "properly wired" to everything in the house, shouldn't something have blown somewhere?

 

[Starex]

If one had 10,000 volts at their ground rod and that ground was "properly wired" to everything in the house, shouldn't something have blown somewhere?

Here Is an article that might help clear up another common mis conception that voltage kills.

https://www.electronicproducts.com/things-only-electrical-engineers-know-its-not-the-voltage-that-kills-you/#:~:text=A%20common%20misconception%20about%20electrical,it%20and%20through%20the%20body.

 

[McKravitts]

So all those "danger high voltage" signs should read "Danger high voltage relative to the ground you're standing on!"?

 

[Starex]

Yes

 

[hwy17]

I recommend binging everything from mike holt on grounding and bonding on youtube.

You don't have to go to your neighbors, the other end of your house will already have a "ground" to ground potential.

 

[McKravitts]

That clears up alot of the confusion. The idea isn't to keep everything in your house at zero volts, but to keep everything in your house at the same voltage.

 

[Starex]

Yes. And that voltage can very dramatically relative to some other location.

 

[McKravitts]

So. let's take a real world situation, one that is a common topic on this forum.
A lot of people have a solar array on a shed, barn, or ground based array. Say the remote array is 100 feet from their house and that the remaining solar equipment is in the house.
The ground potential could be large between the house and the array.
How should the array be grounded, or should it just not be grounded?

 

[hwy17]

So. let's take a real world situation, one that is a common topic on this forum.
A lot of people have a solar array on a shed, barn, or ground based array. Say the remote array is 100 feet from their house and that the remaining solar equipment is in the house.
The ground potential could be large between the house and the array.
How should the array be grounded, or should it just not be grounded?

The array should be grounded to the house ground. There should only be maybe up to 5v between that and the ground under it.

The NEC rather arbitrarily allows a ground rod in addition to the house ground connection. This will create a multipoint grounding system and it's a grey area whether that's a good or bad idea. Mike Holt says he doesn't see the point in it. But if you take pools for example, they also create a separate ground in their required grounding and bonding configuration.

I don't plan to drive a ground rod for my distant array and will only use the house ground.

 

[zanydroid]

Practical Engineering had a good video about grounding recently. He shows a substation grounding system, where it’s mega overkill to try to guarantee that there are no voltage gradients along the floor of the facility.

 

[dianea]

The "code" prevents ground loops, the dark side of grounds.

 

[zanydroid]

The "code" prevents ground loops, the dark side of grounds.

Citation for this?

There are various things allowed / required in code that creates ground loops. And I’m not convinced they matter for line voltage wiring

Ground loops in things like signal shields or single ended data lines for interconnected equipment. But that’s a different type of ground from equipment grounding.

 

[Starex]

Practical Engineering had a good video about grounding recently. He shows a substation grounding system, where it’s mega overkill to try to guarantee that there are no voltage gradients along the floor of the facility.

Could you supply a link to the site?

 

[zanydroid]

Could you supply a link to the site?

 

[Starex]

The "code" prevents ground loops, the dark side of grounds.

Since they allow ground rings around an entire structure, they implicitly allow loops for the earthing system.
Following that same logic, one should be able to treat the remote array and house as a single facility and put in a ring that encircles them both.

 

[Starex]

The principle is that by adding highly conductive material to the less conductive earth, you flatten the voltage gradient.
A single 2 awg bare copper wire running between the house and the array with ground rods attached every 20 feet, will definitely reduce any voltage between them and should at least meet the intent of the code allowing ground rings.