wwhitney
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Re: Nissan/AV L2 EVSE not charging

Sun Feb 20, 2011 11:14 am

garygid wrote:Generally, I believe that the electrical codes only allow a Residence to have ONE single ground (usually 8 feet deep), and all the house grounds must be tied back to that one point.
You're only allowed to have one Neutral-Ground connection, and all the grounding electrodes have to be interconnected, but you can install a supplementary electrode anywhere you want and connect it to the EGC.

In terms of 8 feet deep, if you are using a ground rod, it does have to be 8 feet deep, but one ground rod can't be your only grounding electrode. [Unless you want to go to the trouble to prove that one rod gives a ground resistance of 25 ohms or less, which will take a lot longer than driving a second ground rod.]

Cheers, Wayne

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Ingineer
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Re: Nissan/AV L2 EVSE not charging

Sun Feb 20, 2011 11:51 am

wwhitney wrote:OK, I agree that if you or your neighbor's panel has a direct L1-G fault, and its N-G bond is missing so no breakers trip, then you could get local earth at your car elevated above remote earth by on the order of 60V. Then if you are walking barefoot in a puddle and touch some unpainted metal on the car chassis, you could get a lethal shock.

I would count that as a hard to achieve scenario. Moreover, the resistance of the tires doesn't enter into this scenario, and local grounding isn't really going to help. The resistance to ground of a local ground rod will still be sufficiently large to cause a step potential in the vicinity of the ground rod that could shock you. Earthing is pretty useless for shock prevention at 120V.
I don't agree with your conclusions, but at this point it's just silly discourse, so I'm going to agree to disagree and leave it at that. =)

-Phil
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Ingineer
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Re: Nissan/AV L2 EVSE not charging

Sun Feb 20, 2011 1:40 pm

All this ground rod business reminds me of a "local ground" horror story. When I lived in Michigan, the local codes stipulated an unattached garage must have a local ground (not sure if this is the case everywhere), but definitely relevant to our discussions!

This resident had ~$400 electric bills all the time, even when mild usage was occurring. A quick check of his panel with a clamp-on current meter revealed a 40A "garage" breaker which had around 35A of load on one leg. Upon investigation of the unattached garage, it was found to be largely empty and had nothing capable of that kind of load. There was a small 40A subpanel installed, with only 3 breakers in it, one for lights and 2 for outlets. A deeper inspection revealed the original contractor had made quite a few significant errors:

1. They had ran plastic conduit from the house main panel to the garage but had only included three #8 wires, all black in color, with no ends taped. (violation)

2. There was no separate ground conductor installed in violation of code.

3. The subpanel had it's bonding screw installed, which is not permitted for subpanels.

4. The neutral and one of the hots feeding the panel were swapped, such that the L1 hot was connected to the neutral bar and the neutral fed one leg of the panel. This energized the panel and ground rod with 120V relative to the "true" ground. (and the house)

The breakers were installed such that 2 were on the L1 buss bar (connected to neutral), one for lights, and one for the outlets, of which the garage door opener was connected to. The third breaker was on the L2 bar, and it was thus at 240V over the neutral bar! Luckily only unused outlets were connected to this breaker.

This discovery unveiled a giant resistor formed by the earth that was consuming over 4kw for months on end! (and probably a lot of dead worms)

Had any of the 4 errors not occurred, the problem wouldn't have existed, or would have been discovered right away.
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Smidge204
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Re: Nissan/AV L2 EVSE not charging

Sun Feb 20, 2011 3:29 pm

Ingineer wrote:This discovery unveiled a giant resistor formed by the earth that was consuming over 4kw for months on end! (and probably a lot of dead worms)
On the up side, he never had to shovel a path in the snow from house to garage! :lol:

If that electrician was license, he shouldn't be. A huge electrical bill is probably the best outcome from all that. Yikes.
=Smidge=

wwhitney
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Re: Nissan/AV L2 EVSE not charging

Sun Feb 20, 2011 7:56 pm

Ingineer wrote:All this ground rod business reminds me of a "local ground" horror story. [. . .] This resident had ~$400 electric bills all the time, even when mild usage was occurring. A quick check of his panel with a clamp-on current meter revealed a 40A "garage" breaker which had around 35A of load on one leg.
That is an impressive story, and everyone is fortunate that no one was killed. However, one thing I don't understand. If 35A was flowing from 120V potential difference, then the resistance is a bit under 4 ohms. I would be amazed if that represented an earth path, you'd need to have electrodes at the garage and at the house with ground resistances of only 2 ohms each. Was there some other metallic path between the two structures?

Thanks,
Wayne

wwhitney
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Re: Nissan/AV L2 EVSE not charging

Sun Feb 20, 2011 8:01 pm

Ingineer wrote:I don't agree with your conclusions, but at this point it's just silly discourse, so I'm going to agree to disagree and leave it at that. =)
Well, I'm very much interested in knowing if some of my conclusions are incorrect (particularly "earthing is useless for shock prevention at 120V AC"), but I understand if you want to drop it. Perhaps this is not the appropriate forum. Thanks for the discussion.

Cheers, Wayne

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GeekEV
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Re: Nissan/AV L2 EVSE not charging

Mon Feb 21, 2011 5:02 pm

Good news, everybody! The replacement charger arrived and I installed it. Everything is working just fine now...

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LakeLeaf
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Re: Nissan/AV L2 EVSE not charging

Mon Feb 21, 2011 5:08 pm

MrZorg wrote:Good news, everybody! The replacement charger arrived and I installed it. Everything is working just fine now...
Good news. So I guess the AV technicians aren't coming out tomorrow?

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Re: Nissan/AV L2 EVSE not charging

Mon Feb 21, 2011 5:10 pm

They never called me to schedule an actual appointment. But I emailed them and said not to bother. :lol:

2014 Chevy Spark EV 2LT
2013 Tesla Model S 60kWh[/url]
AV L2 EVSE + kWh meter
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Re: Nissan/AV L2 EVSE not charging

Mon Feb 21, 2011 7:22 pm

Glad it's all resolved. Doesn't bode well for AV's quality though!
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