How to Tell if Service Box is Grounded?

Travelover · Mar 17, 2009

I'm in the process of installing a whole house surge suppressor to my breaker box. In the process, I realized that I don't know for sure if the breaker box is properly grounded. The service entrance / breaker box is located on the above ground wall of a walk out basement. I can see a large (like #6 or so) braided copper wire exit the bottom of the breaker box and head into the finished wall, but I can't see it exit anywhere outside. The basement walls are studded and insulated, covered with drywall. I dug around the base of the wall a foot deep or so and found no wire exiting to a grounding rod.

Before I start cutting into the drywall to trace the wire, does anyone have any suggestions on how I can verify if this wire is grounded?

House was built in 1966, I'm the fourth owner. House has a well, so no grounding to the incoming (plastic) water pipe.

kennyd · Mar 17, 2009

It probably goes to what is called a "footer ground", Basically a piece of rebar that is tied into the footers under the foundation wall. It does NOT go outside.

QRTRHRS · Mar 17, 2009

I think if it was my house, I would just drill a hole through the foundation wall and add a couple of ground rods to what is already there.

carpenter383 · Mar 17, 2009

Take the cover off the breaker box, if there is wiring coming in that's connected to the ground lugs only then it's probably got an earth ground

czechsonofagun · Mar 18, 2009

I had my box grounded, at least that's what I thought, but when I finally got under the back porch for some other reason, I found the grounding wire broken off the spike.
Please, do not take chances and make sure it IS grounded and all the connections are good and sound.

Lasgambler · Mar 18, 2009

kennyd said:
It probably goes to what is called a "footer ground", Basically a piece of rebar that is tied into the footers under the foundation wall. It does NOT go outside.

As mentioned by kennyd it would be grounded to the rebar in the footing. Out here it is called a "youfer" probably the incorrect spelling. Code now states that the clamp on the rebar should be accessible by an access panel. I think if you cut the drywall just above the footing, below the panel, you will find the ground clamp. Good Luck.
Terry

Travelover · Mar 18, 2009

Lasgambler said:
As mentioned by kennyd it would be grounded to the rebar in the footing. Out here it is called a "youfer" probably the incorrect spelling. Code now states that the clamp on the rebar should be accessible by an access panel. I think if you cut the drywall just above the footing, below the panel, you will find the ground clamp. Good Luck.
Terry

Right, I think this is correct. My concern is whether 43 years on, the ground is still solid. I was hoping someone had a clever way of verifying the integrity of the ground, but I suspect it takes a fairly sophisticated piece of electronic equipment to do so. I may just end up punching a hole in the wall, pushing out a new wire and attaching it to a couple of grounding rods.

QRTRHRS · Mar 18, 2009

czechsonofagun said:
I had my box grounded, at least that's what I thought, but when I finally got under the back porch for some other reason, I found the grounding wire broken off the spike.
Please, do not take chances and make sure it IS grounded and all the connections are good and sound.

I would want to be sure there is sufficient moisture in the earth for a rod under a porch. Adding a second rod is not that expensive for the extra measure of added safety.

By the way, a T-post pounder is a great way to get an eight foot ground rod buried to a depth where you can more easily finish it with a sledge hammer.

Redbug · Mar 18, 2009

Make sure when you connect your cable to the rod, use brass hardware, (includes screws, etc). Steel with the cheap galvanized coating will deteriorate with time and the connection will become unsound. Lowe's, Home Depot sells both-it's a little bit more but get the brass.

JB4310 · Mar 18, 2009

I've heard about rebar grounding but never seen it, What I often see is a regular ground rod in the floor under the panel, which are installed before the floors are poured, even more common is a ground wire in a conduit hanging on the foundation wall and leading to a clamp on the city water service line.

My new 200 amp service has 2 ground rods outside 10 feet apart, must be code now?

JB.