Installing a Second Electric Meter for EV Charging

9 years ago

My utility allows a second meter (on a separate rate) for EV charging. I've currently got a 400A service (2x200A). The overhead feeder comes into a raceway, to a pull box, then to the meter, then to the 2x200A panel. The second 200A breaker supplies a sub-panel at the other end of the house that can live on 100A. My utility won't let me have more than 400A, so I anticipate being required to reduce the one breaker to make room for the second meter under a 400A service total ceiling.

I propose to tap the utility side feeder in the pull box to supply a new RV-type meter/breaker panel that I will use for EV Charging.

1. Disconnects. If I have 4 or fewer breakers in the new EV panel, plus the two disconnects in the existing household panel, I presume I won't need a separate disconnect for the RV panel since I'll be at 6 or fewer throws to disconnect the combined service. Right?

2. Bonding vs not boding the second meter panel. I'll tap the three wires from the utility in the pull box ahead of the existing meter to feed the EV meter panel, but, do I bond the neutral and ground in the new EV meter panel, as well as in the household panel, and let the neutral wire carry the ground back to the household panel that is in turn connected to earth ground? Or, do I bond them in the EV panel AND run a separate ground all the way back to the UFER? Or, do I leave neutral and ground unbonded in the RV panel, and run a separate ground back to the household panel and the ground bar, or directly to the UFER? Note that the new panel will be mechanically connected via metallic conduit to the existing pull box, not that one would use that as a ground path. Just information.

I've never addressed a multi-meter situation. This will all be permitted and the utility service planner is coming out next week to assess. Any insights appreciated.

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Comments (3)

Ron Natalie
9 years ago
First thing to do is ask the PoCo if they have any installation requirements. They will trump all when it comes to the placement, wiring, and configuration of the meter.

Frankly, I'm not sure exactly what you are proposing. Normally, you are not permitted more than one "service" in a structure. There are a few exceptions in the NEC, none would seem to apply for an EV meter.

So, I'm going to start assuming that we're talking about a single service here. Yes, you are right that there six throw rule. If between the "main panel" and your "EV panel" you can shut off the power to the entire service with six handle throws or less, you can do this if the panels are located together. If they aren't colocated, you have a bunch of other problems.

As for ground-to-neutral bonding. You must bond at the service disconnect so, in the above scenario, both panels would have the bond jumper.

Now it is possible that your AHJ may permit the EV charging drop as a separate service. In that case, each one stands alone (you have a separate six throw rule for each one), and both definitely need be grounded.

The another possibility is that the utility will say NO to your plans and mandate a single disconnect ahead of the taps for your existing service and the new EV meter.
jumper
Original Author
9 years ago
Thank you. Yes, there is a single overhead service coming down the mast from the utility into a pull box that is there split to two separate meters. Thanks for the clarification on the grounding and six throw. I'll clarify also with the utility service planner and the AHJ.
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jumper
Original Author
9 years ago
Its all finished. The service is tapped in the service entrance gutter with Polaris connectors and the second meter panel is fed from there through an SLB and has its own grounding wire run to the UFER. The AHJ inspector didn't inspect a dang thing. All he said was that he didn't think he needed to come back since there were no GFIs to test given these are 50A NEMA 14-50 outlets. He made me promise to repair the drywall inside the garage and handed me a final sign-off.

The utility came by today to drop the service so I could make up the taps.