Grounding temporary panels

[102 Inspector]

Our community wants to provide temporary load centers for downtown events such as parades and festival events. These would be 100 amp panels set up on portable stands, fed with 4-wire assemblies and intended to be plugged into a permanently installed receptacle for power. Would each of this locations be required to establish a new grounding electrode system or is the 4-wire adequate for grounding. All of them will originate from a main panel location. Since each of this portable panels could be considered a separate structure I am thinking an electrode system might be required a each location. Still in preliminary design but requesting any thoughts.

 

[tom baker]

We used construction spiders for that type of application. had about 20 but each time set up required a permit and inspection, so went with SS boxes with 8 GFCI receptacles in them.

 

[petersonra]

Our community wants to provide temporary load centers for downtown events such as parades and festival events. These would be 100 amp panels set up on portable stands, fed with 4-wire assemblies and intended to be plugged into a permanently installed receptacle for power. Would each of this locations be required to establish a new grounding electrode system or is the 4-wire adequate for grounding. All of them will originate from a main panel location. Since each of this portable panels could be considered a separate structure I am thinking an electrode system might be required a each location. Still in preliminary design but requesting any thoughts.

Is a feeder allowed to be fed from a receptacle? Just curious.

I agree it is a structure. You are probably going to have to create a grounding electrode system for each one. It will probably need to be two ground rods 6 feet apart. The irreversible connection requirement is going to make it messy.

 

[infinity]

I would call a panel on a stand equipment not a structure. The 2017 NEC clarified what classifies as a structure.

Structure. That which is built or constructed, other than equipment. (CMP-1)

 

[tom baker]

The fact that its temporary does not change the code requirement for grounding and bonding, its a feeder panel. Now if you can use a spider, then a grounding electrode system is not required.
On your comment about the 4th green wire, that is for bonding, ground rods are for lightning.

 

[petersonra]

I would call a panel on a stand equipment not a structure. The 2017 NEC clarified what classifies as a structure.

I agree the equipment is not"structure" but the stand they build to mount in on certainly is.

 

[jumper]

I do not see it as a permanent structure, no GES required IMO.

Quite a common set up.

Tom’s spider boxes are great but if you are building them, make sure you use all the correct parts, not gonna list all the stuff, assuming you know what is involved.

Biggest concern to me is making sure stands are properly secured so they do not tip over. Easy to do, stakes and what not.

A small roped or cautioned taped “fence” around the stands also. Don’t want people, bikes or whatever knocking into them.

 

[jumper]

The fact that its temporary does not change the code requirement for grounding and bonding, its a feeder panel. Now if you can use a spider, then a grounding electrode system is not required.
On your comment about the 4th green wire, that is for bonding, ground rods are for lightning.

Not trying to be smart alecky, but if there is an outdoor event and a storm with lightning is coming, it prolly is gonna get canceled or postponed. OP is in mid west, they are smart about stuff like that because tornadoes can easily follow.

 

[petersonra]

I do not see it as a permanent structure, no GES required IMO.

It seems to me that as a temporary installation, article 590 applies.

590.1 Scope. The provisions of this article apply to temporary
electric power and lighting installations.
590.2 All Wiring Installations.
(A) Other Articles. Except as specifically modified in this article,
all other requirements of this Code for permanent wiring
shall apply to temporary wiring installations.

So unless this article specifically exempts a temporary structure (with more than one circuit) from having a GES, it is still required by code. I looked through article 590 and did not find any exemption to the GES requirements.

The best arguement against the GES requirement might be the wording of "served" as regards the structure. If nothing on the structure is served by any of the circuits one might make an argument that a GES is not needed.

 

[jumper]

Assuming these are just basic 1-3 day events, no one I have ever heard of was running around driving rods into local parks, near sidewalk or whatever.

If these were large commercial events like major fairs or such, I would agree, but a small parade with a few floats, a marching band and like that is over in 3 hours. Nope.

Even a two day tomato festival is not a likely to be a major venue.

 

[don_resqcapt19]

I agree the equipment is not"structure" but the stand they build to mount in on certainly is.

I see the support for the panel as part of the equipment. I think the change in 2017 was aimed straight at things like this.

 

[infinity]

I see the support for the panel as part of the equipment. I think the change in 2017 was aimed straight at things like this.

I agree, we're talking about a portable panel on a portable stand which is the support for the panel.

 

[jumper]

I agree, we're talking about a portable panel on a portable stand which is the support for the panel.

Yep and said equipment is only going to be used in a limited capacity and for a short duration.

 

[Little Bill]

Is a feeder allowed to be fed from a receptacle? Just curious.

I agree it is a structure. You are probably going to have to create a grounding electrode system for each one. It will probably need to be two ground rods 6 feet apart. The irreversible connection requirement is going to make it messy.

What irreversible connection are you talking about?
A panel, ground rod and GEC doesn't require irreversible connections.

 

[George Stolz]

I see the support for the panel as part of the equipment. I think the change in 2017 was aimed straight at things like this.

Agreed. The one good that came from the change.

 

[102 Inspector]

The change in definition would definitely be a bonus, however I am in one of those states that is still under the 2008 NEC. Since this is preliminary at this point for electrical demands, I am taking these comments to heart when reviewing the project. Have always appreciated the support from this site. Thank you.

 

[kwired]

Is a feeder allowed to be fed from a receptacle? Just curious.

Isn't that what you have with a mobile home (where allowed) or RV plugged into a 50 amp 120/240 volt receptacle

I would call a panel on a stand equipment not a structure. The 2017 NEC clarified what classifies as a structure.

I agree.

Another thing I have run into is at the small community hospitals that haven't shelled out the $$$$ for MRI equipment around these parts, there are companies that have MRI equipment in a semi-trailer. I have hooked up an outlet to plug these into - the one's I have been involved with were a 200 amp 5 wire pin and sleeve device and carrying 480/277 to that trailer. IIRC we only had 150 amp OCPD on it, still didn't look all that fun to be the truck driver and pull out that heavy cable assembly to plug it in when he arrives.

 

[jumper]

Another thing I have run into is at the small community hospitals that haven't shelled out the $$$$ for MRI equipment around these parts, there are companies that have MRI equipment in a semi-trailer. I have hooked up an outlet to plug these into - the one's I have been involved with were a 200 amp 5 wire pin and sleeve device and carrying 480/277 to that trailer. IIRC we only had 150 amp OCPD on it, still didn't look all that fun to be the truck driver and pull out that heavy cable assembly to plug it in when he arrives.

It would depend on the duration that trailor was planted there for me.

The ones around my old medical place were there for awhile, talking 6-18 months during remodel.

If it 30 days or more, I would be putting in a GES in that case.



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[kwired]

It would depend on the duration that trailor was planted there for me.

The ones around my old medical place were there for awhile, talking 6-18 months during remodel.

If it 30 days or more, I would be putting in a GES in that case.



a

These are only there for a few hours and then leave. May be there a couple times a week or so.

Used to be a mobile CT scanner that came around and used the same outlet, but most the hospitals now have their own CT equipment.

I never been inside trailer to know what is in there, and hope I never am - that probably means I'm the patient.

 

[jumper]

These are only there for a few hours and then leave. May be there a couple times a week or so.

Used to be a mobile CT scanner that came around and used the same outlet, but most the hospitals now have their own CT equipment.

I never been inside trailer to know what is in there, and hope I never am - that probably means I'm the patient.

I have a vested interest. I am a patient.