ECN Forum
Posted By: bwise121 Service grounding - 09/11/03 10:53 PM
I'm helping a friend upgrade two panels on a duplex he owns. The panels are right next to eachother. Each panel will be 100 amp.
The plan is to go up with one riser rated for 200 amp and bring that into a gutter. From the gutter, split into two 100 amp panels below.

I'm familiar with grounding for regular single family homes, but in this case I'm not sure if I'm needing to double up all the grounding.

I don't have a ufer so I'll use the water main as the main grounding electrode (it is metal going into the ground), secondary electrode will be a 8' ground rod. Lastly, I'll bond the gas at the hot water heater. All of this will be done in #4 bare wire.

This being said, I'm sure I don't have to put in two ground rods and run two #4 wires to the water for each panel. How is this normally done?

Any suggestions or advice on this would be appreciated... also, what is the differnece between grounding and bonding?

Thanks,
Posted By: zapped208 Re: Service grounding - 09/12/03 10:13 AM
What is a ufer? We do not use that term here in Pa or Ny. Thanks.
Posted By: jnsells Re: Service grounding - 09/12/03 12:30 PM
The grounding electrode conductors can be spliced together in the gutter, then one grounding electrode conductor run to your grounding electrode(s), with the size based on a 100 amp service. Of course, the gutter has to be bonded also. Soares book on grounding has good illustrations of this.

Although the code requires gas piping to be bonded, several AHJ's and local gas companies will not allow this.....best to check first.

For our friends in PA & NY, a UFER is a concrete encased grounding electrode, typically rebar within the foundation. The UFER ground system was actually developed during World War II by Herbert G. Ufer, a retired vice president of U.L.
Posted By: bwise121 Re: Service grounding - 09/12/03 11:05 PM
Although some interesting comments I'm not finding this helpful.
Example of the kind of explaination I'm looking for follows:
Take the Grounding electrode and the conductor from the ground rod to one panel then take a grounding jumper from the first panel to the second panel.

Please reply,
Byron
Posted By: Electricmanscott Re: Service grounding - 09/13/03 01:12 AM
If it's do it yourself info you need you might be in the wrong place. By the way where are the meters? I can think of no reason to have a gutter.
Posted By: Scott35 Re: Service grounding - 09/13/03 02:53 AM
I agree with Electricmanscott, especially since jnsells' post answers the question concisely.

Sorry if this sounds offensive (which it's not intended to be at all!).

Scott35
Posted By: bwise121 Re: Service grounding - 09/13/03 03:55 AM
No offense taken. I guess I was looking for someone to say point A goes to point B. I have purchased some electrical books and I am educating myself. This is a very useful board and I intend to use it in the future.

As for the gutter, I'm only following the advice of fellow electricains that have done similar work. I guess the idea is to have one riser. The existing panels are right next to eachother, so it would make sense for the riser to come into the gutter and then each conductor into a landing lug then to the line side of meter.

Sound okay?

Many thanks and have a good weekend.

Byron
Posted By: PCBelarge Re: Service grounding - 09/13/03 05:44 PM
Byron
Your bio does not state your occupation, I am curious why? This leads the pros here to be cautious as to how much info they give, because all the info given to a novice or homeowner will still not be enough. There is so much more to this industry than point A to point B!

Pierre
Posted By: Electricmanscott Re: Service grounding - 09/13/03 06:34 PM
For a two family I would use a 2 gang meter socket. One 200 amp riser from that, a hundred amp feeder to each panel. I see no need for a gutter at all. This is all the info I can give as this is NOT a do it yourself project and while it is good to see you trying to learn, this board and some books are not going to make you an electrician. If I lived in that duplex I would not be happy to know the wiring is being done by some handymen. In fact I would notify the local authorities.
Posted By: bwise121 Re: Service grounding - 09/13/03 06:57 PM
LOL very funny. Sorry to misguide you as to thinking I'm a handyman by the fact that I'm helping a friend out. I'm a licensed electrician here in California. This isn't my expertise so I was trying to find some info on grounding multi-family homes. I mostly have done commercial and single family homes. Again, the idea of a gutter with two 100 Amp panels was new to me and thats what I was told to do by fellow electricians as stated in a previous post.


Byron
Posted By: bwise121 Re: Service grounding - 09/13/03 07:06 PM
Sorry PCBelarge, I didn't see your earlier reply. I probably should be straight forward and ask my question. I thought it was a simple one and I'd look stupid if I had stated that I'm an electrical contractor. Sorry for the confusion it was my fault. I did infact update my profile to state my occupation thanks for letting me know.

CSL #820270 http://www2.cslb.ca.gov/CSLB_LIBRARY/license+request.asp

Check that againt my profile.

Byron
Posted By: caselec Re: Service grounding - 09/13/03 07:37 PM
Bryon

I agree with E-Scott about not using the gutter. Use a 2-gang meter center which holds a feeder breaker for each meter and make your grounding electrode connection here. From the meter center install 4-wire feeders to each unit and use main lug load centers. Since your in Northern CA these meter centers should be very easy to find. If your supplier does not have any in stock they can get one in a couple of days.

Curt
Posted By: Bill Addiss Re: Service grounding - 09/13/03 07:38 PM
Byron,

We're all here to help each other.
There's no need to feel sheepish about asking a question like that as no one here knows everything. I've been Licensed for about 20 years yet learn something new almost every day.

Welcome aboard.

Bill
Posted By: russ m Re: Service grounding - 09/14/03 01:58 PM
If the panels are right next to each other, why not run to the # 4 from the water meter. and loop it to both panels Into #1 out of #1 into #2 and bond each panel. You could do the same with the supplemental ground, or just run the supplemental ground to the water pipe

[This message has been edited by russ m (edited 09-14-2003).]

[This message has been edited by russ m (edited 09-14-2003).]
Posted By: russ m Re: Service grounding - 09/14/03 02:26 PM
When I first posted I had #8 for the ground, because the wire from the meter to the 100 amp panel would be #3.
I know the 250.66 says that the grounding conductor is based on the service entrance conductor.
Article 100 says the service entrance conductor is the service conductors between the terminals of the service equipment and a point usually outside the building, clear of the building walls.
If you had a 400amp service, with six meters, feeding six 100amp breaker panels with mains, and all the conduits ran under the concrete to panels in each dwelling. Would you require a #8 ground to each panel or would you require a 1/0.
Posted By: triple Re: Service grounding - 09/16/03 04:10 AM
You state that the panels are right next to each other but you do not mention how far they are from the meters. In fact, you never even mention using any meters at all!

If the panels are right inside the home close to the meter location (w/in 8' in WI) then there is a cheaper/easier method than already mentioned. Use a double meter socket with 4/0 Al or 2/0 Cu up a single mast. There is no need to have OCP within the meter as long as the service entrance conduit is short. Run two 1 1/4 PVC’s from double meter to each panel inside. Use 3 #4 Cu or #2 Al conductors from each meter to its respective panel. Do your neutral to ground bonding in each panel (usually a green screw provided with the panel). You only need #8 Cu to run from the water pipe to each panel. One wire will suffice but you have to use an irreversible splice (such as a crimp) when you turn that one wire into two to attach to both panels. The wire to the ground rods (you have to use two in WI) also only needs to be #8 but, if the wire is not protected outside, you will need to use at least a size 4 Cu. Bare #4 copper works best for most residential ground rod wires because it doubles as a readily accessible grounding location on the outside of the home for such things as telephone and satellite dishes.

After rereading your posts, I don't think I completely understand your situation. Since you say that you are an electrical contractor, there is absolutely no way you could have forgotten about installing a meter socket. That would be about as likely as an electrician forgetting how to install a lightbulb! Apparrently, there must be a single meter elsewhere on the property and the rental units are not separately metered. But if that were the case, now would be the time to rectify the situation which, of course, you should also know. Something is not adding up. Please fill us in on the secret.
Posted By: bwise121 Re: Service grounding - 09/16/03 05:00 AM
I was planning on going with an all-in-one panel for each unit. Since then, others have suggested the dual meter panel which I like better. I'm going to look at one tomorrow at the supply shop. Thanks for your input.

Byron
Posted By: sparky Re: Service grounding - 09/16/03 10:28 AM
Quote
also, what is the differnece between grounding and bonding?

[aside]a conceptual issue with many rop's moving toward cleaner terminology[/aside]
Posted By: triple Re: Service grounding - 09/18/03 04:08 PM
Don't forget to bond around the water meter. Place a water pipe bonding clamp on each side of the water meter and run your #8 through each.

In my area, the electrician does NOT bond gas piping in any way (commercial or residential). Maybe there are exceptions here but they must be few and far between.
© ECN Electrical Forums