~Grounding a Panel~

Hello Everyone!

I've been reading through a ton of posts on these forums for the past 2 days & feel like I know half of the top posters now, love how friendly and helpful everyone is. I tried to find answers to a bunch of questions I have, but wasn't able to find anything super specific (although there's always overlap).

I could put the questions up piecemeal, but to just to try to be as clear as possible, I'll just list my questions by number and whoever feels like taking a shot at even one of them, I'd be most appreciative!

Also, I'm in Missouri...I believe our town is operating from 2005 or 2008 NEC (probably the latter).

I have a 4-gang meter base installed around 1960 servicing 4 separate apartments. From the main service meter base to each apartments sub panel is 100 amp 3-wire. Because of a bunch of updates to 2 of the apartments (new carpentry/moved panel location/rewired apartment), I'm required to install updated 4-wire from the main meter to the updated apartments service panel. (PICTURE OF PANEL HERE: View image: old panel clear )

Overall Question: When I run the new 4-wire into the meter base/service panel (replacing one of the existing 3-wires) how would I properly ground the meter base?

Questions #1: I'm almost sure I'll need to install a grounding rod, right?
Question #2: Do I need to attach a grounding bar (Or something? ...gec? egc? ...difference?) inside the meter base (like on the inside wall) and run the new grounds (from the 2 new 4-wires that will be coming in) + the wire from the grounding rod to it, then bond the neutral bar and grounding bar?

Question #3: What about the existing 2 units that are still on 3-wire. Would those be fine to just leave with the two hots going to the breaker, and the neutral to the neutral bar?

Question #4: Any idea what that one ground wire is going from the neutral bar to the inside of one of those 3-wires is? I'm guessing it's a ground to a pipe inside the building or something...?
Question #4.5: I noticed on a new meter base installed at another building (with 200 amp service) that they put a grounding rod in, AND had a thick wire from the neutral bar attach to a copper water main in the basement. Is this always code? Having two grounds like that?

I know it's a lot of questions, but I've been trying to piece together answers and figured it would be better to just come right out and ask them clearly. Again, any and all help is appreciated. Thanks so much!

 

If the picture shown is at the meter all of the units should have already been fed with a 4 wire feeder. That is the service panel where all of the bonding and grounding should have taken place.

Two means of grounding are common if you have a metallic water line in contact with the earth for 10' or more. One goes to the water line and another typically to a ground rod.

 

Sorry for not making that clearer. Here are two more pictures of the main service panel/meter base a little more zoomed out:






This is the meter base, but the wires feeding the individual apartments are only 3 wire 100amp. (It was built in the 60s).

 

In your lower picture I see the neutral/ground bar. I see a bonding strap from the meter pan to that bar on the left. I don't see any grounds connected to that bar.

 

Your 4-gang meter socket is already 50 plus years old and well beyond it's useful life. You should seriously consider replacing the whole assemby with a new one. You will not find a new unit in that same configuration so I would have a contractor plan ahead to replace the two feeders and the 4-gang socket in one day. Your two existing tenants will be without power for one day, but that is better than an emergency replacement later where they could easily be without power for several days. I would suggest replacing the 4-gang unit with a large NEMA 3R junction box to cover the area where the feeders exit the building and mounting a new 4-gang assemby to either the right or left and connecting the junction box to the meter assembly with conduits. The junction box will house all necessary splicing of feeders. Your contractor shoud have no problem getting the two tenants back in service within one day. Most of the installation of the two new 4-wire feeders can be completed ahead of the planned outage day to replace the metering assembly. This is also the best time to upgrae grounding to current code.

Just curious, what city are you located in?

 

GEC -- Grounding Electrode Conductor -- The ground wire that goes between panel and ground rod (or main water pipe as it exits the house underground or certain other buried items not including gas pipes) and the panel, or ground wire that goes between ground rods and/or aforementioned water pipe. A GEC must run from the panel where the first master disconnect including one apartment's main breaker is located.

EGC -- Equipment Grounding Conductor -- The ground wire that accompanies branch circuit conductors and/or power cord conductors from outlet boxes or equipment down to the panel. (In a few instances it might not accompany the associate circuit conductors and/or might be attached to a GEC rather than a panel bus.)

GES -- Grounding Electrode System -- All of the ground rods, metal water pipe exiting the house underground (at most one required), and comparable qualifying grounding electrodes i.e. concrete encased, the GECs (interconnecting them) and panel busses to which the GECs are attached. Each building has its own GES or in a few instances might not need one. GECs need not run between buildings even when EGCs do.

Bonding Jumper -- A ground wire that interconnects items, notably pipes, so that if one of those items should get energized, any current will have a path (possibly including other pipes) ultimately to a GEC.

Generally, if A is bonded to B and B is bonded to C then A is bonded to C. However certain bondings require specific kinds and routings of wires.

 

Thanks for your responses guys...
AllanJ, thanks for the breakdown... I've been curious as to the differences for a while. It's really helpful! :-)

& Casual Joe, we're located in the St. Lou area.
Ideally, we could put a new meter base, but if we were to just leave the existing one, how would you ground it?
I'm guessing that we'd need a grounding panel bus for all the grounds, with a grounding rod, .... ???

 

In most municipalities and all unincorporated areas of St. Louis County the county issues the permits and does the inspections, they are very by-the-book and will require a permit to be taken out by a licensed contractor. If there are any questions on what the county might want, the contractor will contact the inspector for that area. My guess is that once you touch the meter socket the county will require the grounding be brought up to 2008 NEC which means the neutral must be grounded from the meter socket (where the first disconnects are located) to both a ground rod (1 ground rod...1/2" X 8' is Ok) and water service entry into the building. There will have to be a bonding jumper from the neutral bus to the metal can and a ground bar installed for the EGC in the two new 4-wire feeders to be terminated to. All 4 unit panels will be treated as subpanels. IF they allow the first two 3-wire feeders to remain, there is a question of how they were originally grounded and how the county wants those handled. This is a question for your contractor to ask. That being said, there are some municipalities that do not contract electrical inspections to the county and issue their own permits and employ their own inspectors. If I knew what municipality these aprtments are in I could tell you who issues the permit and performs the inspections by the St. Louis County matrix.

I think most contractors would suggest replacing the 4-gang meter socket.