Outside equipment grounding requirements

[JCB1001]

We added a piece of equipment (about 40 ft by 40 feet by 60 feet tall) containing 480 VAC industrial blowers, electrical control panels that house PLCs and computers and sit outside and 80 feet from our main manufacturing building. The question is how do we ground this piece of outside equipment. Our industrial engineer had instructed electrical contractors to drive about 5 grounding rods into the ground but they are not bonded under the outside concrete pad. There are 5 grounding wires sticking above the concrete pad. He will be instructing the contractor to cut the 5 grounding wires( i.e not intend to use the outside grounding rods). Instead they decided to run a bonding ground wire from the outside equipment structural steel to the existing main manufacturing building ground grid.
Do you see any problems here?

 

[petersonra]

We added a piece of equipment (about 40 ft by 40 feet by 60 feet tall) containing 480 VAC industrial blowers, electrical control panels that house PLCs and computers and sit outside and 80 feet from our main manufacturing building. The question is how do we ground this piece of outside equipment. Our industrial engineer had instructed electrical contractors to drive about 5 grounding rods into the ground but they are not bonded under the outside concrete pad. There are 5 grounding wires sticking above the concrete pad. He will be instructing the contractor to cut the 5 grounding wires( i.e not intend to use the outside grounding rods). Instead they decided to run a bonding ground wire from the outside equipment structural steel to the existing main manufacturing building ground grid.
Do you see any problems here?

I am not entirely sure what you are saying here.

If the structural steel qualifies as a grounding electrode it has to be bonded to the grounding electrode system.

What was the purpose of the 5 grounding rods? That seems kind of silly unless it was part of some lightning protection system. If it was part of the LPS, how can they just unbond them?

in any case, if there are ground rods present they have to be bonded to the GES even if they are not required.

 

[infinity]

If this is a permanently mounted 40'X40'X60' structure I would connect it to a GES just like a building.

 

[GoldDigger]

in any case, if there are ground rods present they have to be bonded to the GES even if they are not required.

Once you have made it impossible to connect to them (by cutting off the wires) are they still present?
If you drill out the top foot, would they still be present or would they disappear by becoming too short?

 

[petersonra]

Once you have made it impossible to connect to them (by cutting off the wires) are they still present?
If you drill out the top foot, would they still be present or would they disappear by becoming too short?

How is it impossible to connect to them just because you cut off the wires?

In any case they are still there and qualify as GE.

250.50 Grounding Electrode System. All grounding electrodes
as described in 250.52(A)(1) through (A)(7) that are
present at each building or structure served shall be bonded
together to form the grounding electrode system.

There is no provision that I can see to disqualify them as GE just by cutting the wires to them. If you shortened them they would no longer qualify as GE and thus would not have to be bonded to the GES.

 

[GoldDigger]

How is it impossible to connect to them just because you cut off the wires?

In any case they are still there and qualify as GE.

I believe that OP said that the electrodes were driven before the concrete was poured and only the wires came up through the slab.
No wires, no connection unless you hammer out the concrete to get to the electrodes.

 

[infinity]

If you cut them off then just bang in two new ones and forget about the old ones.

 

[jumper]

If you cut them off then just bang in two new ones and forget about the old ones.

Too easy of a solution, we gotta figure out a hard way to do it.

 

[petersonra]

I believe that OP said that the electrodes were driven before the concrete was poured and only the wires came up through the slab.
No wires, no connection unless you hammer out the concrete to get to the electrodes.

How do you get around the requirement that you connect to all existing GE?

Unless you physically remove them or cut them so they are too short to qualify as a GE they are still there, even if someone poured concrete over them.

I still wonder why they were put there in the first place. Five is just not a number of ground rods someone would come up with at random.

 

[ptonsparky]

How do you get around the requirement that you connect to all existing GE?

Unless you physically remove them or cut them so they are too short to qualify as a GE they are still there, even if someone poured concrete over them.

I still wonder why they were put there in the first place. Five is just not a number of ground rods someone would come up with at random.

Five is all they had in the truck.

 

[kwired]

Five is all they had in the truck.

IIRC they are in bundles of five at the supply house so ...one bundle:happyyes:

 

[ghorwood]

Piece of equipment?

Piece of equipment?

How is the equipment fed? Why wouldn't you connect it to ground with an Equipment Grounding Conductor, just like any other "equipment"? :?

 

[kwired]

How is the equipment fed? Why wouldn't you connect it to ground with an Equipment Grounding Conductor, just like any other "equipment"? :?

I guess there is a little confusion or at least misuse of terms. I think the discussion is about grounding electrodes, though the term "equipment grounding" is in the thread title.

 

[augie47]

I think the installation falls back to the NEC definition of a "structure".
If the 'assembled' equipment is not structurally connected to the main building it becomes a separate structure and grounding electrodes would be required by 250.32 along with a equipment grounding conductor from the supply.
If it does not qualify as a separate structure then the equipment grounding conductor from the main building would be all that is required and any additional grounding would be supplemental.