mitch672
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Re: Introduction!

Tue Apr 27, 2010 2:09 pm

Gavin,

you should just put a 100-150A subpanel in the garage, then breakers/wire can be run off that panel to the EV charger(s)

of course it depends on the size of the service in your house, you can't run a 150A subpanel of a 100A main panel :)
2012 Advanced Plug in Prius (sold)
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sjfotos
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Re: Introduction!

Tue Apr 27, 2010 2:24 pm

Very interesting discussion. I had been discussing 8 gauge with my electrician. Reading through Karen, dees and mitch's posts, I may well go higher. Thank you. Steve
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Gavin
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Re: Introduction!

Tue Apr 27, 2010 2:39 pm

mitch672 wrote:Gavin,

you should just put a 100-150A subpanel in the garage, then breakers/wire can be run off that panel to the EV charger(s)

of course it depends on the size of the service in your house, you can't run a 150A subpanel of a 100A main panel :)


Ha...yes, just last year redid the main panel (the old one was 45 years old). We were adding a pool to the back and needed some more amperage and also wanted to move the panel from the back of the house to the side. Our old box was only 100A. Our new box is 200A. So we have some power to spare. Though not 150A :) .

We do have a small subpanel in the garage to run the air and heat and some other stuff...I think it only has a 30A line running to it...I could make that bigger and rerun a bigger line to it. Maybe that should get a 3 gauge wire? Having 85A to the garage subpanel should allow for 50A to a car charger and still leave 30A for the air and heat and washer and such.

Gavin

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sjfotos
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Re: Introduction!

Tue Apr 27, 2010 2:46 pm

Wow Gavin,
All I know is that I sure don't want to be the guy who wrestles a 3 gauge line from my panel to the garage and that is a short run! Very interesting....all sorts of things for me to think about here....thanks for the original question....
Steve
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mitch672
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Re: Introduction!

Tue Apr 27, 2010 2:53 pm

sjfotos wrote:Wow Gavin,
All I know is that I sure don't want to be the guy who wrestles a 3 gauge line from my panel to the garage and that is a short run! Very interesting....all sorts of things for me to think about here....thanks for the original question....
Steve


Steve, It's worse than that, you have at least (3) conductors, netural, hot, hot, and in some cases the electrical inspector will make you run a #8 ground as well (bonding), you would need at least a 2" conduit (bigger is better), and a cable puller, you can't real do it by hand.

I was thinking about this very issue, and was thinking of asking if my utility is going to have "EV charging rates" (off peak/time of day), and perhaps just put in another meter to a new panel in the garage, just for use for the EV(s) chargers, there is another "customer" monthly charge, however if the EV/TOD rate may be low enough to offset that...
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I Support OpenEVSE: http://code.google.com/p/open-evse/
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garygid
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Re: Introduction!

Tue Apr 27, 2010 5:57 pm

The electrical wiring codes are ... sometimes strange. And all wiring should be permitted, at least before connection, I suspect. And, the local codes can vary.

To avoid having to tear something out, I suggest getting professional approval of your design. Bigger might seem better, but is not always allowed.

I had to remove the 150-amp input breaker on my 150 amp service box, and replace it with a 110-amp breaker when I added a 40-amp breaker to connect my 7kW PV system into the service box. So, now at night, I can only draw 110 amps, not 150! The reason, a 150-amp "rated" metal "service" box is not allowed to have more "possible" input than the box's rating.

And, if I wanted to put in a higher-capacity service box (even if I stayed with the original 150-amp breaker), SDG&E said that they would require me to trench out to the street, approx 28" deep and lay in a conduit. They would inspect and pull in the new wires required for the (potentially) larger demand. The trench would have to cross all the other utilities except water (gas, phone, cable, and the existing electrical conduit).
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drees
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Re: Introduction!

Tue Apr 27, 2010 6:29 pm

garygid wrote:I had to remove the 150-amp input breaker on my 150 amp service box, and replace it with a 110-amp breaker when I added a 40-amp breaker to connect my 7kW PV system into the service box. So, now at night, I can only draw 110 amps, not 150! The reason, a 150-amp "rated" metal "service" box is not allowed to have more "possible" input than the box's rating.

Warning - getting OT here!

Actually, with PV there is a 20% exception - you are allowed to exceed the busbar in your panel (which typically has the same rating as the panel) by 20% when backfeeding power for residential applications. This is explicitly allowed by the NEC. The only caveat is that the breaker should be located at the opposite end of the bar as the main breaker. This is to avoid overloading any one section of the busbar. The theory is that if you short out your busbar, no section of the bar will see more than the busbar rating.

So if you have a 150A panel/breaker, you can use a 30A breaker to feed in your solar power. Of course, since you need a 40A breaker for a 7kW PV system, that still means you have to downsize your main breaker, but you should only have to downsize it by 10A to 140A.

150A * 120% = 180A - 40A = 140A. 140A breakers aren't common, but 125A breakers are so you would be safely able to get another 15A from the electric company if you wanted.

garygid wrote:And, if I wanted to put in a higher-capacity service box (even if I stayed with the original 150-amp breaker), SDG&E said that they would require me to trench out to the street, approx 28" deep and lay in a conduit. They would inspect and pull in the new wires required for the (potentially) larger demand. The trench would have to cross all the other utilities except water (gas, phone, cable, and the existing electrical conduit).

I ran into that issue, too with my house. I currently have a 100A panel and the main feed wires are only rated to 125A. Upgrading to 200A service means running new wires (which are buried) up to the latest code in a trench to the street. At the street, the trench actually needed to be 3" deep thanks to the handhole it would be connecting to. There are all sorts of crazy requirements for the trench - only 2 90* bends allowed, 2" PVC conduit, feed entrance can't be within 3" of the gas meter (and right now my gas meter is right under the main service panel), has to be filled with proper material, etc.

Quote I got would end up being like $6,000 to do the work. Ouch! It's the only time I wish I had overhead lines - upgrading those are easy in comparison.

I suspect that these sorts of issues will be fairly common when people start getting pre-checks done to see what it will take to get a 240V 20-40A charger hooked up.

My breaker box is full after adding my 3.24 kW PV system. Hopefully I can get away with a 125A main service feed to get the charger. Actually, if I can get a 200A box with a 125A main breaker, then I'll have plenty of room to upgrade my PV system in the future. :) 200A * 120% = 240A - 125A = 115A of PV power - about a 22 kW system. :) I'll run out of roof space long before I get anywhere close to that. :)
'11 LEAF SL Powered By 3.24 kW Enphase Solar PV

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garygid
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Re: Introduction!

Wed Apr 28, 2010 4:49 am

Thanks, I did not know about the 20% exception for PV, or how to calculate it.
I will check with the local building dept to see if it applies here.
Another 30 amps would be great.

Since I am also out of room for breakers, I might put in a sub-panel right on the back of the in-wall, exterior-facing main panel, and move some breakers into the sub-panel.

Is there a limit on the sum of the load-breakers in a box?
Does not seem to be.
See SOC/GID-Meter and CAN-Do Info
2011 LEAF, sold in 2015
2010 Prius, 2014 silver Tesla S
Nissan EVSE, mod to 240/120v 16A
PU: SDG&E
Solar PV: 33 x 225W -> 7 kW max AC
To Sell: X-treme 5000Li EV motorcycle

darelldd
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Re: Introduction!

Wed Apr 28, 2010 5:18 pm

So back to the subject... I hate to see a whole forum section built around company participation... but with no participation. :(
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Gavin
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Re: Introduction!

Wed Apr 28, 2010 6:39 pm

I would give Jess a bit of slack on that point. Remember that this site has just recently had a big jump in posting and thread creation. I'm sure Jess tended to just peek in from time to time to see if anything needed addressing. Now she really could look in each day and find new questions to look into...heck she could check a few times a day like I do...but that is a new development, and I'm sure she needs some time to realize that and make the proper adjustments.

Also, I think this is an unofficial LEAF site, so any contributions by actually Nissan staff is a nice bonus. It will be great if Nissan is a common posting presence here, but most sites don't get that. Nissan would be wise though to post here often...it helps them as much as us. Helping to shift and structure the conversation is a good thing.

Gavin

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