Grounding Issue in an SDS

[SparkRay]

Hello,

I am installing a small (60A) sub panel in our work shop. The plant is powered by an ungrounded Delta system. The 480VAC feeds a set of transformers and steps down to 240 3 phase. This feeds a bus that distributes to various things. I want to add a small 12 circuit panel of 208 VAC single phase. I am using two phases of the 240 off of the bus.

The problem I'm having is that we have no ground or neutral pulled through the building. I want to install a ground rod at the panel but I got through the concrete and hit ledge about 24" down. There are no ground rods anywhere on the premises that I'm aware of.

How can I create a ground? I was thinking of using the building beams but do not know if the anchor bolts even contact the soil. Or, is that not necessary?

Also, can I use the sprinkler system piping as a ground?

Thanks in advance for your help.

Ray

General Hammond: "O'Neil, what the hell are you doing?" O'Neil: "Right in the middle of my backswing?!?!"

 

[7anoter4]

In my opinion, you have to run a copper conductor outside and to connect it with an electrode made as per NEC art.250. A pvc conduit will be necessary in order to protect the grounding electrode conductor. In my opinion also, it would be better to consult a licensed electrician.

 

[itsmoked]

I'm trying to understand what you mean by

hit ledge about 24" down

?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[SparkRay]

Ledge is what they call bedrock in the Northeast. Very few places can go 8' deep around here without hitting ledge/bedrock.

General Hammond: "O'Neil, what the hell are you doing?" O'Neil: "Right in the middle of my backswing?!?!"

 

[waross]

You can break out some concrete until you expose a rebar. Clean the rebar and connect to it. Patch the concrete. Test the ground resistance.
If there is enough continuous rebar to make a good connection to the concrete the concrete will make a good ground.
Look up Ufer in Wiki.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Yep, that's a good ground system, very effective.
I think a lot of new houses in my area are built that way.


And, thanks for explaining the 'ledge' to me SparkRay. I had no idea that was a Northeastern phenomenon.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[SparkRay]

It's called ledge mostly because it sticks out like ledges all over the place. I had to have half of my home's foundation site blasted to fit the foundation.

I found several places where there is a ground rod in place and then tied to the building's main columns. I should be okay tying to the columns.

General Hammond: "O'Neil, what the hell are you doing?" O'Neil: "Right in the middle of my backswing?!?!"