Seperate Meter for EV - grounding method question

[YourElectricianOC]

I'm a newer electrical contractor, who has been using the forum as a lurker for some time now to get explanations of things that might not be so clear in the NEC. Great forum!

I've run into a situation that no one local seems to be sure of.

I have a customer wanting a seperate meter installed for their 100A Electric Vehicle Charger. It's from an underground feed, so far the plan is to install a pull box between the Socal Edison transformer and the 200A installed panel, (directly under the 200A panel), and install a second 100A meter/panel next to the 200A panel as a separate SE, fed from the pull box below the original panel. As a SE, I know it will have to be grounded to both a grounding electrode and the water line, but my question is do I have to run a seperate ground all the way to the electrode in the ground and water line? Or can I feed the ground through the pull box and into the grounding circuit in the 200A panel? Would this be considered a "bonded" connection and inadeqaute? I put a call into the inspector at the local AHJ, but they didn't get back to me yet and are closed on Fridays. The customer wants the proposal by the weekend, and it is a lot faster (i.e. less expensive) to run to the original panel than clear down the house where the nearest water pipe is.

I do appreciate your input!

 

[YourElectricianOC]

What I learned from the inspector - while it is technically not a "separately derived system" as defined in the NEC, it still requires its own separate ground rod and EGC (which I put in anyway, just to be safe).

 

[electrofelon]

I'm a newer electrical contractor, who has been using the forum as a lurker for some time now to get explanations of things that might not be so clear in the NEC. Great forum!

I've run into a situation that no one local seems to be sure of.

I have a customer wanting a seperate meter installed for their 100A Electric Vehicle Charger. It's from an underground feed, so far the plan is to install a pull box between the Socal Edison transformer and the 200A installed panel, (directly under the 200A panel), and install a second 100A meter/panel next to the 200A panel as a separate SE, fed from the pull box below the original panel. As a SE, I know it will have to be grounded to both a grounding electrode and the water line, but my question is do I have to run a seperate ground all the way to the electrode in the ground and water line? Or can I feed the ground through the pull box and into the grounding circuit in the 200A panel? Would this be considered a "bonded" connection and inadeqaute? I put a call into the inspector at the local AHJ, but they didn't get back to me yet and are closed on Fridays. The customer wants the proposal by the weekend, and it is a lot faster (i.e. less expensive) to run to the original panel than clear down the house where the nearest water pipe is.

I do appreciate your input!

So if I am understanding correctly, you intend to add a second utility meter, and a second service disconnect (which will need to be grouped with the original one)? You are allowed to tap the service entrance conductors and have two sets of service entrance conductors to two separate grouped service disconnects. Many people have trouble with the grounding details for multiple service enclosures so you are not alone, however the NEC is very clear on this and in article 250 has a section on this and gives you basically three options: 1) connect your GEC to the service conductors before they split 2) Use the grounding electrode conductor tap method or 3) run a GEC to each enclosure. How many GEC's do you have now - I assume one to the rods and one to the water line? IT sounds to me like the tap method would be the easiest so you could run a #6 from the new enclosure to the original enclosure and use a split bolt to attach it to the existing GEC(s). I would have to check the wording but I believe it would need to attach to the GEC directly not the "neutral bar". Note that the GEC(s) to the 200A enclosure must remain without a splice (hence why I said split bolt). If I may ask/propose another option, have you considered just buying your own personal meter for the EV's branch circuit to keep track of its usage? You could get a utility type meter or get an inductive type like a emon dmon......

 

[electrofelon]

What I learned from the inspector - while it is technically not a "separately derived system" as defined in the NEC, it still requires its own separate ground rod and EGC (which I put in anyway, just to be safe).

I dont see what separately derived systems have to do with anything here - technically, not technically, literally, figuratively, or remotely IT would be a violation to have its own ground rod and not connect it to the existing grounding electrode system.

 

[GoldDigger]

And if the neutrals of the separate meter outputs are connected together (except through bond to the common GES) then they will not be separate systems (they cannot be separately derived systems since they all are actually services.....)

Sent from my XT1080 using Tapatalk

 

[scott thompson]

Contact SCE Service Planner

Contact SCE Service Planner

YourElectricianOC

You should contact SCE and discuss your Project with a Service Planner, before continuing.
The Service Planning Office to contact will be located in the "General Information" tab of the current ESR Manual (Electrical Service Requirements).
If you do not have a copy of this, you may download one from the SCE site, via the following link:

ESR Manual

As to the GES, the only Compliant method will be to Bond the 2nd Service to the Grounding Electrode System, via a single Grounding Electrode Conductor (#6 cu. most likely).

The Bond may be terminated at any convenient location, as specified in Section 250.50.

--Scott (EE)

 

[kwired]

What I learned from the inspector - while it is technically not a "separately derived system" as defined in the NEC, it still requires its own separate ground rod and EGC (which I put in anyway, just to be safe).

It is not a separately derived system, it is the same system the other disconnect is supplied from. All you are doing is changing it from a service with a single disconnecting means to a service with multiple disconnecting means. There is more than one way to connect the grounding electrode system with multiple disconnecting means, but simplest way is generally to connect to a common point on the supply side of the disconnecting means. Next simplest is to run a common GEC and make taps to it from each disconnecting means.