UFER Questions...unusual installation

[Mr onetwo]

Location #1 -
I am prepping the site and getting ready to pour concrete for my new shop and I have a couple of questions on UFER's. I will have a 6" thick slab with 12" thickened edges and 1 internal 12" grade beam to carry a mezzanine wall. It will be completely insulated with the usual 2" XPS and will get Pex for radiant infloor heat. If I leave out the XPS under a 20' section of the grade beam and tie into the rebar so there is direct contact with the earth...is this a good location for the UFER? Alternatively, I could put a 20' pc of #5 rebar in concrete below the thickened edge before insulating and pouring the slab. It would be more exposed to moisture in the perimeter...just not sure which would be better. Keep in mind that ground rods are not an option...granite ledge 41" below floor level.

Location #2 -
I am bringing the electrical service into a 40' shipping container and the ledge situation is about the same...46". It is about 200' away from where the shop is located. We will be pouring 4 14" concrete piers under the 4 corners. I think I will pour a 20' pc of concrete with #5 for the UFER and bond this to the container and the service if the utility will accept this. Is this ok? Are there any additional things I should do for lightning protection?

I found the proper approved grounding clamps here - https://www.suppliesdepot.com/product/greaves-j31-db-6-20-5-direct-burial-rebar-ground-clamp-58-inch
It will be a 150 amp service with a Square D RC12L200C meter/main with a HOM2150BB 4 pole disconnect and 2" rigid mast on the container. I have a 150 amp panel with feed thru lugs to go over to the shop.

Thank you in advance for your thoughts.

 

[mike93lx]

Ground rods don't have to be driven straight down.

I wouldn't be pouring extra concrete just to install a ufer

 

[dave*99]

250.53(A)(4) Rod and Pipe Electrodes​

The electrode must be installed straight down for at least 2.44 m in length, contacting the soil. Connecting a 2.44-long rod above the ground surface will not comply with the rule.

Where encountering rock bottom, the electrode may be pushed at an oblique angle not to exceed 45° from a vertical line–keeping at least 2.44 m of its length inside the ground.

When encountering rock bottom at an angle up to 45°–making it impossible to keep 2.44 m of electrode inside the ground–the electrode is permitted to be buried horizontally in a trench at least 0.75 m​

 

[billconner]

Interesting discussion. Because from what I've read an ufer is considered more reliable than a ground rod, I like your leaving insulation out under grade beam. No poly either.

As far as the container, I don't know how permanent it is that there is any concern on reliability of ground rod, but still like your plan.

 

[Chuckster in NJ]

UFER ground is better than ground rods……… Easy to do.

 

[billconner]

What I don't know, under the container, can you bend the rebar into a "U" that is 10' long and maybe 8 to 12" wide? Mine was an "L" because it went around a corner.

 

[dave*99]

What I don't know, under the container, can you bend the rebar into a "U" that is 10' long and maybe 8 to 12" wide? Mine was an "L" because it went around a corner.

I don’t think that meets the intent of spacing rods so they don’t influence each other. The 2 legs of the U are too close to each other.
Just as 2 ground rods need separation, 2 rebars in concrete would need an electrically equivalent separation. The concept is the voltage gradient (which drives the current flow) must diminish to zero between 2 rods/rebars.

 

[billconner]

I don’t think that meets the intent of spacing rods they don’t influence each other. The 2 legs of the U are too close to each other.

Not rods, a concrete-encased electrode - rebar in concrete in contact with the ground.

 

[dave*99]

Not rods, a concrete-encased electrode - rebar in concrete in contact with the ground.

Yes I understand that. There is a voltage gradient in soil as well as in concrete. A 10 ft. U that is 12” wide is probably not electrically equivalent to a 20 ft straight rod. The legs of the U would need to be spaced such that the voltage gradient fell off between the legs as they do in the ground rod diagram. I don’t have a distance number for that and my opinion is irrelevant if the code specified something else.

The point is if the legs of the U are too closely spaced it performs like a straight 10 ft run.

 

[Mr onetwo]

The container is permanent so I am going to the expense of pouring piers under the corners with plates to weld to.. I know ground rods would be cheaper but I think the UFER is a more reliable solution. Here is what CMP requires for the meter/main.I am going straight into the container with a 2" chase ******...do I need to use a grounding locknut at this location? No LB as shown in drawing.

 

[Mr onetwo]

Another question I have deals with the location of the panel in the shop. Instead of bring 2" pvc up inside the exterior wall or on the outside, is there any reason why I can't or shouldn't bring the pvc up thru the said grade beam and mount the panel in the mezzanine wall. With the UFER directly under the wall this would be very efficient I think.

 

[mike93lx]

Another question I have deals with the location of the panel in the shop. Instead of bring 2" pvc up inside the exterior wall or on the outside, is there any reason why I can't or shouldn't bring the pvc up thru the said grade beam and mount the panel in the mezzanine wall. With the UFER directly under the wall this would be very efficient I think.
View attachment 2337042

The meter has to be outside, so you can't do this for the meter main but if it's a separate panel, bringing the pipe up indoors is good.

 

[Mr onetwo]

The meter/main is on the container , not the shop

 

[mike93lx]

The meter/main is on the container , not the shop

Send it. I'd bring the pipe up inside the shop for sure