Bonding to existing panel ground

[trader4]

I'm helping out a friend with a new house who wants to add surge protection. The plan is to use a whole house AC surge protector at the panel and a seperate cable coax surge protector located a few feet away where the cable enters the house.

The question is, how to tie the seperate coax protector to the house ground? There are actually two 150 amp panels next to each other. The service comes into a long narrow metal box between the two panels, which in turn feeds the two 150 amp panels. There is a heavy gauge copper ground wire that runs from this narrow metal box into the concrete basement slab. So, what is the correct, code compliant method to bond to this?

Can I buy some type of bolt on connector that I can slip over the exposed existing ground wire outside the box and secure another ground wire to it and then run over to the coax protector? That would seem to me to be the preferred method, if permissible.

Or can I bond to the ground inside one of the breaker panels and run a ground wire from the panel out to the coax protector?

[The Daring Dufas]

It really depends on your local codes but common practice is to use a split bolt to bond the coax protector to the #4 copper ground wire coming out of the power panels. You can also run it to the ground rod and use another rod clamp for your protector ground wire. Some city/county engineering departments may have requirements that are more strict than the National Electrical Code or I've come across some that are very slack. I've worked in some areas where there was no inspection except for the power company. You might call your local inspector and just ask. All of them I've ever met would be glad to tell you their local requirements. As far as running it into the power panel, all of your cable/telecom installers are not going to open your power panels and will always look for an external connection.

TDD

[jamesgangnc]

You should be able to get a split bolt connector that lets you attach to the exposed ground lead. I would not run it inside the panels as that will generate all sorts of questions.

[gfretwell]

I would suggest moving into the 21st century and install an inter system grounding block. (2008 code) This is a terminal strip that has a "lay in" lug for the grounding conductor you are talking about and several terminals for attaching other grounding conductors. The home store should have one but any electrical supplier will if they don't

[trader4]

Actually the house was built in the 21st century, only 4 years ago. But I guess they finally updated the code to something logical that all new homes should have.

Anyway, thanks for the help. That is exactly what I need. A little googling produced this:

[gfretwell]

Yup that is what I was talking about. You can see that is a lot more elegant than a bunch of split bolts.

[The Daring Dufas]

That's exactly what you can use. Cool new product, I haven't seen it in the electrical supply houses or the big box stores yet.

TDD

[bud--]

If I was doing it, I would just use a split bolt as others have suggested. You want to minimize wire length to the common connection point.

If the "coax surge protector" is just a ground block, which is used where cable enters the house, it doesn't include surge protection. The voltage on the center wire can rise until it arcs across at the F connector - about 4kV. There are cable surge protectors (which may be what you have).

You are installing the service panel suppressor at one of the 150A panels?

Generally keep the leads from the surge suppressor short.

The wire to the slab should be a "concrete encased electrode", commonly called a Ufer ground. It is one of the better ones.

[bud--]

The NEC generally requires a concrete encased electrode (Ufer ground) for new construction. (It also still requires using a water pipe as an electrode if there is 10 ft of metal in the earth.)

My only suggestion, which I gave before, is generally to minimize the length of earthing wire from panel to the block and from the phone and cable entrance protectors to the block. Sounds like you are doing fine.

[trader4]

Yes, we are going to buy a coax surge protector.

Yes.

And where it's located it will be real easy to install one of the inter-system bolt-on grounding blocks that gfretw recommended.

[JIMMIE]

Where I live you cant take this type of ground into the service panel. It must go directly to the ground rod. There are rules about how far away it can be from the rod too.

Jimmie

[jamesgangnc]

How's that work when the ground is a line tied to the foundation rebar instead of a rod? Cause that's how a lot of new construction is being done now. Can you attach near the point the line goes into the block?

[trader4]

Hide quoted text -

That's exactly what the inter-system grounding blocks are designed for. I guess the remaining question is if anyone is going to bitch about exactly how close to the grounding electrode one places the grounding block. In my case, the logical place would be right beneath the panel, about 4 ft. which seems reasonable to me. I could mount it lower, but then I'd have to secure another plywood mounting board to the blocks. Much easier if I just put it under the panel. Don't see that it makes any difference anyhow, as the total length of wire from the cable coax surge protector or anything else that gets connected to ground is going to be the same anyway.