Grounding and Bonding Issues-Steel Building

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blue spark

blue spark

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Hi folks! Got a couple of questions regarding metal buildings. What I have here is a post and beam Morton building. 2- 200amp services general/off-peak. On the metal framed steel buildings we always make the frame part of the grounding system. There is no metal framing on this building. There are no footings. The slab (6") will float on top of 2" of certifoam to insulate the wirsbo in the slab. So this slab is not in contact with earth. ?#1 20' of #4 bare in the dirt under the foam plus #6 solid bare to a rod outside going to satisfy code? Water line is plastic. ?#2 Since there is no metal frame, I'm assuming I have to bond both sides of the "skin" to the panel. I cannot find this in the code. Last year we were told we had to do this on another building. Where is this rule located?
 
The wording for grounding electrodes is "all available"- that said- if it is there, use it, if not I guess you can't. Would be curious to see a concrete slab on top of foam:confused:
 
Pretty common up here for floor heat installations. Takes a little extra on the ground work but it works.
 
barbeer said:
... Would be curious to see a concrete slab on top of foam...
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More and more is being constructed on top of "lightweight fill" ... Geofoam ... which is essentially the same material as a styrofoam coffee cup.

Pretty interesting stuff when you actually see it in-use on a big project.

VA DoT just installed a small mountain of it up here holding up a new section of US-1.
 
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20' of #4 in the dirt is not a grounding electrode. If you're attempting to make a ground ring it, among other things, it must encircle the entire structure. If you so choose you can simply use two grounding rods for your grounding electrode system.
 
infinity said:
20' of #4 in the dirt is not a grounding electrode. If you're attempting to make a ground ring it, among other things, it must encircle the entire structure. If you so choose you can simply use two grounding rods for your grounding electrode system.
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OK, that's kind of what I was realizing today I was driving home. The 20' bare #4 had something in the wording encased in concrete in contact with earth or something close to that. What about bonding the interior and exterior skins of the building?
 
The metal frame of the building, when present, qualifies as a grounding electrode. Since you don't have one, the skin would have to be likely to be come energized to require bonding.
 
barbeer said:
... Pretty interesting- is it sprayed or in sheet form? ...
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It's produced at an off-site plant in whatever form is spec'd by the project.

The project here looked like a modern-day version of pyramid building; using "good-sized" blocks (maybe 8'x6'x4') with quite a bit of hand-fitting required to fill the voids and fit the contours.
 
barbeer said:
Pretty interesting- is it sprayed or in sheet form? Is it acceptable to do the 20' of copper as OP stated or do you just hit 2 Grd rods and be done with it?
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It's sheet foam. Basically they're very careful with the groundwork. It's tamped 2 times to grade then fine tuned. This is what is refered to as a floating slab up here. Otherwise the sand below the slab acts like a heat-sync during cold weather and sucks the heat right out of the slab. When floor heating really came around up here, this prep was rarely done and there were major issues with boilers and elec cables/mats running 24/7 :grin: Hate to get that electric bill. There's also another product that resembles bubble wrap except is has a foil face on one side. The foam gives a better R value though.
 
infinity said:
The metal frame of the building, when present, qualifies as a grounding electrode. Since you don't have one, the skin would have to be likely to be come energized to require bonding.
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Would lightning be considered as energized? We seem to have a surplus of that up here:grin:
 
Sorry about the SA remark although it is an issue but the BO isn't going to pay for a lightning system. I thought it might be a good idea to bond the skins though. As I said an inspector told me we had to at one point on another building. I could understand his reasoning but couldn't find the article.
 
You will probably be installing some sort of electrical outlets, disconnects, etc. on or near the metal surfaces, so I say bond them, but be certain that the interconnections and laps of the metal panels are electrically continuous, or you may need to install a whole bunch of jumpers.
 
It should be good but I'll test to make sure. The laps are screwed every 2' verticle. On a 50*60*24 I'm hoping there's enough continuity with all those screws!
 
blue spark said:
Hi folks! Got a couple of questions regarding metal buildings. What I have here is a post and beam Morton building. 2- 200amp services general/off-peak. On the metal framed steel buildings we always make the frame part of the grounding system. There is no metal framing on this building. There are no footings. The slab (6") will float on top of 2" of certifoam to insulate the wirsbo in the slab. So this slab is not in contact with earth. ?#1 20' of #4 bare in the dirt under the foam plus #6 solid bare to a rod outside going to satisfy code? Water line is plastic. ?#2 Since there is no metal frame, I'm assuming I have to bond both sides of the "skin" to the panel. I cannot find this in the code. Last year we were told we had to do this on another building. Where is this rule located?
Click to expand...

A slab is never a CEE anyway. Only the foundation is. I would bet even money that somewhere there is a footing for the walls to sit on. If it has rebar in it, it qualifies as a CEE and you have to connect to it.
 
petersonra said:
A slab is never a CEE anyway. Only the foundation is. I would bet even money that somewhere there is a footing for the walls to sit on. If it has rebar in it, it qualifies as a CEE and you have to connect to it.
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Negative on the footings. There are none in this building type. I believe 20' #4 bare encased in a concrete slab in contact with earth does meet the requirement for an electrode. Correct me if I'm wrong :roll: Wouldn't be the first time. The AHJ wants two rods driven so there you go.
On a side note, I brought the #6 bare GEC in the building from below grade and protected it with EMT up to the panel. I was informed that this creates a choke? He "suggested" I put it in sched 80 pvc instead. Anyone ever heard of this?
 
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