240 outlet for 2022 leaf EVSE question

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BillAinCT said:
You don't have anything in your house that draws 15A or 20A yet your house is chock full of 15 and 20A breakers. You can have a 40, 50, 60, even 70A breaker on the right gauge wire running to your EVSE outlet to accommodate the Nissan EVSE.

Probably true, but there can be multiple outlets and lights on one breaker and using common wire
 
I think that using the example of general purpose circuits here is a bit inappropriate. Sure, most circuits are not designed to protect the device(s) for the reasons given. But with a specialized circuit like that for an EVSE, why not size the breaker to offer some protection for the device? The circuit has one device, and one device only, so why not make it do the best job it can: i.e. protect the wires and offer some protection for the device? After all, you don't see 50 amp dryer circuits, except in those few cases where you have a 30+ amp dryer.
 
alozzy said:
I would genuinely appreciate an electrician explaining why the consensus is to run a new 50A circuit rather than to make use of the existing 30A circuit and an adjustable EVSE.

For many people living in a townhouse or an older home, a 100A main panel is standard. In such cases, the electrician will almost certainly want to upgrade the panel.

In contrast, using an existing 30A circuit, with a 24A limited EVSE, incurs no new wiring costs nor panel upgrades. It also allows the LEAF to charge at 87% of full L2 rate. Selling the Nissan supplied EVSE makes it a zero cost option...

I realize that cost isn't everything, but a $2000 unexpected bill (panel upgrade, wiring, labor, etc) for a new EV owner isn't fun and the pay back period isn't great either...

I see posts like this over and over again, so a sticky post by an electrician, covering the range of options, would be an excellent resource for future EV owners. It would also make it easier for MNL members to direct new members to the sticky post, like we do with LeftieBiker's excellent post.
I have a large house with almost all electric service (except for the gas stove and HVAC backup heater). That includes a 60A instantaneous water heater for the solar hat water backup. The main house is on a 100A service with another 100A subpanel for the spa. Even with all this, the most power I've ever pulled from the Mains is 20KW for 15 min. 83A at 240VAC A all totaled. Typically on a monthly basis, max loading is loading is around 10-13 KW with most of the time it being much lower. Most people grossly over estimate their power usage. think about what your average power usage is. Probably less than 2 KW. 100A Service is more than adequate for most homes even with a EV.

Most of the time panel upgrades are more about more breaker space or meeting a code requirement (adding PV to a 100A service could overload a 125A bus in an existing breaker box for instance). I recently upgraded a 100 amp outdoor panel to a 200A panel. The old panel was corroded and I wanted more spaces for breakers. The cost for a 200A panel instead of a 100A panel was less than $50 difference. I also replaced all the old breakers with new ones just because they were 30 years old. The panel is still fed by a 100A breaker This new panel feeds the house, garage, utility sheds, pond pumps and my EV charger all on a 100 amp service.
 
johnlocke said:
I have a large house with almost all electric service (except for the gas stove and HVAC backup heater). That includes a 60A instantaneous water heater for the solar hat water backup. The main house is on a 100A service with another 100A subpanel for the spa.
...
I recently upgraded a 100 amp outdoor panel to a 200A panel. The panel is still fed by a 100A breaker This new panel feeds the house, garage, utility sheds, pond pumps and my EV charger all on a 100 amp service.

I'm interested in how this all is wired. Could you start from the utilitie's meter(s) and explain how each panel is fed/connected ?
 
SageBrush said:
johnlocke said:
I have a large house with almost all electric service (except for the gas stove and HVAC backup heater). That includes a 60A instantaneous water heater for the solar hat water backup. The main house is on a 100A service with another 100A subpanel for the spa.
...
I recently upgraded a 100 amp outdoor panel to a 200A panel. The panel is still fed by a 100A breaker This new panel feeds the house, garage, utility sheds, pond pumps and my EV charger all on a 100 amp service.

I'm interested in how this all is wired. Could you start from the utilitie's meter(s) and explain how each panel is fed/connected ?
It's complicated. At the meter I have a 200A pedestal mount panel (required by SDG&E) that feeds 2 100 amp subpanels and the 60A water heater. The first sub panel is actually my battery backup system and a 9KW PV array. That feeds a 100A automatic transfer switch for the 20KW backup propane generator which in turn feeds the 200A subpanel for the house, outbuildings, L2 charging station, a second 9KW PV array, and the pond equipment. Even though the panel is rated for 200A it is fed though the 100A transfer switch. The PV array has a max theoretical 32A current so that subpanel could have as much as 132A on the bus. Never happens in practice but meets code requirements. The second subpanel is just for my hot tub and low voltage lighting. I may get around to adding a charging station to it in the future.

There additional subpanels in the house and in most of the outbuildings. Point is that I've got a lot of stuff and live on a 5 acre farm with a well and septic. I use nearly 30,000 KWH annually and have never come close to 100A draw. Most people use less than 1/3 of what I do.
 
^^ Wow

That maps out like a small industrial plant ;)
Sounds nifty !
Thanks for sharing.

Out of curiosity -- when you say you use 30k kWh a year, is that the net consumption from the utility despite your 18 kWh of PV ?
 
SageBrush said:
^^ Wow

That maps out like a small industrial plant ;)
Sounds nifty !
Thanks for sharing.

Out of curiosity -- when you say you use 30k kWh a year, is that the net consumption from the utility despite your 18 kWh of PV ?
That's total consumption. PV provides about 90-95% of the power I use. Most of the SDG&E consumption is in Dec-Jan. With the new battery backup system I only use SDG&E between midnight and 9AM unless the weather is bad. I am on net metering but SDG&E keeps trying to get rid of it. If they succeed in that, I'll have to consider adding another 8-9KW of PV so I can be 100% solar even in Dec-Jan. I really only need 2K more to cover my current shortfall overall but to cover Nov though Feb without any power From SDG&E requires a 9KW array due to short days and bad weather. If SDG&E changes their rate structure to only pay me wholesale rates for power I input and retail for power I pull back out, then I might find it cheaper to install more PV rather than pay them.
 
Since we're way off topic here already.....are your panels ground mount? Are the ponds used for hydro power at all?

I ask because I'm thinking of buying my dad's farm and going 100% PV. I'll ground mount the panels but haven't decided on whether to grid-tie, use batteries or try to do micro-hydro and I'm always interested in other's solutions.

I see you also like sub-panels. I have one now and am planning to install 2 more this summer. They make wiring so much easier in many ways and the cost is negligible and well worth the cost IMHO.
 
^^ Awesome.

Interesting to hear that you can cover your winter shortfall by adding only more kW and not having to also add more storage.
I doubt many people can say the same
 
I have panel banks connected to battery storage and panel banks connected to grid-tie, and am always interested in the net power generated and sold to the power grid...... as I see it now the grid-tie is more efficient because it sells all produced power back into the grid, whereas the battery system has 2 inefficiencies: the batteries themselves are not 100% either charging or releasing, and the inverter which governs the battery system does not immediately sell the power back into the grid when the batteries are full. This latter issue actually makes a fairly big difference because the battery bank gets charged, the inverter takes a bit of time to switch over to grid sell, the batteries get drawn down a bit selling, it takes a few moments to switch back to charge mode, etc. I could probably fine tune all of this but the point is to use the batteries not simply keep them charged. Bottom line: grid-tie is more efficient, batteries give us more security for when power is out (which is not often, so....)
 
SageBrush said:
^^ Awesome.

Interesting to hear that you can cover your winter shortfall by adding only more kW and not having to also add more storage.
I doubt many people can say the same
I'm in SDG&E's Sunrise power corridor. That gives me access to grant money to pay for the battery backup system. That is supposed to pay $1/WH for storage capability up to a max limit based on my highest 1 hour power draw for the past year. I maxed out the capacity so I have 84KWH of storage, That's enough to get me through an entire day even with no sun at all. if I have some daylight for the PV I can recharge the battery and run the house. If I have several really bad days of weather the backup gen would kick in. As long as I'm tied to SDG&E it's cheaper to recharge off the grid then to run the gen set. The most likely scenario is that SDG&E shuts off power due to a wildfire but I've got plenty of sunshine so the PV system charges the battery back up during the day and runs the house and everything else. At night the battery discharges some but gets topped back up the next day. I don't even notice the power shutoff unless I look at the control software.

If it wasn't for the grant money I wouldn't have gotten the battery backup. I would have stuck with the backup generator. But as long as SDG&E is going to pay for it I might as well take advantage of the program. The downside is that the wiring is convoluted, the electronics require some monitoring, and my wife has no idea how it all works and wouldn't know what to do if something goes wrong.
 
But as long as SDG&E is going to pay for it I might as well take advantage of the program.

Is this like the Tesla Powerwall in that your power company, in return for its incentives, can draw your batteries down during peak demand? I believe that my neighbor can have his Tesla drawn down about 10 to 15% whenever the power company chooses.....
 
dmacarthur said:
But as long as SDG&E is going to pay for it I might as well take advantage of the program.

Is this like the Tesla Powerwall in that your power company, in return for its incentives, can draw your batteries down during peak demand? I believe that my neighbor can have his Tesla drawn down about 10 to 15% whenever the power company chooses.....
Nope, this is part of their wildfire mitigation program. SDG&E doesn't get to touch the battery backup. Actually as long as I don't use the batteries to buy and sell power, they have a 25 year warranty. If I use it to buy cheap power at night and then sell it back to SDG&E during peak usage periods, the warranty drops to 10 years. The units are built by SunFusion here in San Diego. I had originally tried to get Powerwalls but first they were on backorder then they were only available with the purchase of a PV system.

Someone asked about the mounting system. There are two separate arrays. The first was installed 11 years ago and consists of 33 panels on a ground mount with a Sunnyboy inverter. The second one is also ground mounted and consists of 30 panels hooked to APS micro inverters. No single point of failure, no high DC voltages, better MPP tracking, and are simple to install. If the Sunnyboy ever fails I'll probably replace it with micro inverters as well. Altogether, it's 18.5KW of panels and 17KW Max AC output. On the best days, noontime power is about 15-16KW. The amount of sun I get is nearly equal to Death Valley, ideal for PV.
 
Thanks for the info. I was aware of the high DC voltages using string inverters but I guess I never thought about the single point of failure aspect. That is a good selling point for a micro-inverter setup. Plus I do like the monitoring functionality also.
 
Sunnyboy and their clones are a thing of the past- we have 4 of them and will be replacing them with the newer tech when and if they fail...... Ah well, it was the best available at the time!
 
I am a fan of SMA string inverters for their reliability, cost, way less and much simpler cabling compared to micros, and less energy loss due to much lower amperage. SMA also has a built in, simple and free 2 kW grid-down connection.

Micros and SolarEdge took over the residential market due to the requirement for panel level shutdown on roof mounts. Ground mounts do not have that requirement but they are a small fraction of the residential market.
 
For my micro setup the wiring couldn't get much easier. It uses 2 runs of 12 AWG THWN in conduit from the roof to a sub-panel in the attic. The cabling for the panels just plugs in like a kit and then that cable terminates in a J-box where it connects to the THWN. If I want to squeeze 2 more panels onto the existing setup, I just plug them into the existing cabling and I'm done. If I add another bank of panels, I'll just run another set of THWN to the sub-panel. I'll have to up-size the wire from the attic sub-panel to the service panel but that will take 20 minutes.

In my case I also have some partial shading at certain times of day. The micro's alleviate that although I guess there are 'optimizers' for string setups that can do the same thing, although I'd bet that using those negates any cost advantage of using a string inverter.

I also don't mind not having to worry about running 400+V DC lines around. 240V split-phase can kill you but it's much safer than 400V DC, IMHO.

That said, for a ground mount system it may make sense to use strings. I'll have to see how much the cost differential is since at this point, that is the only advantage I can see. I never thought about efficiency gains but I can't imagine that they are huge.
 
goldbrick said:
The micro's alleviate that although I guess there are 'optimizers' for string setups that can do the same thing, although I'd bet that using those negates any cost advantage of using a string inverter.
Optimizers are the SolarEdge solution. Regular panels these days have bypass diodes that protect the MPP setting for the unshaded panels so that particular advantage is a lot less than marketing suggests. I think the difference ends up being less than 5%, and depending on conditions, a lot less than 5%

Resistance losses are proportional to length and proportional to the quadratic of amperage. A series arrangement will be around 10 Amps for the run to the inverter while in the parallel arrangement the ~ 1.5 Amps/ panel sum.
 
SageBrush said:
I am a fan of SMA string inverters for their reliability, cost, way less and much simpler cabling compared to micros, and less energy loss due to much lower amperage. SMA also has a built in, simple and free 2 kW grid-down connection.

Micros and SolarEdge took over the residential market due to the requirement for panel level shutdown on roof mounts. Ground mounts do not have that requirement but they are a small fraction of the residential market.
I used APS microinverters. A 240 trunk cable runs between the inverters which just plug in to it. 10 panels , five inverters per trunk line. 3 trunk lines back to the breaker box, each on a separate 20A breaker with a 40A master breaker. It's pretty simple. Be aware that APS is not set up to deal with DIY'ers so you need a dealer to set up your account and register the web interface controller. The inverters will work just fine without it but you can't monitor the system without it. The monitor connects wirelessly to the inverters but needs a wired ethernet connection.

Micro inverters convert to AC at the panel so DC losses are minimal. SMA string inverters are cheaper by a few hundred dollars then the equivalent Micros but not having to work with HVDC and no single point of failure balance that out for DIY'ers.
 
johnlocke said:
Micro inverters convert to AC at the panel so DC losses are minimal. SMA string inverters are cheaper by a few hundred dollars then the equivalent Micros but not having to work with HVDC and no single point of failure balance that out for DIY'ers.

The wire resistance losses are proportional to the square of the current. 10 awg copper resistance is about 1.25  ohms per 1000 ft. Your string has about 2x the current as a a DC solution, and then 4x more current after two strings are combined. A rooftop is almost certainly close enough to the inverter to not bother considering but a ground mount may be a different story.

E.,g. if two 20 Amp strings are combined near the panels and then 40 Amps run 250 feet to the inverter, the loss will be
40^2*2*1.25*250/1000 = 1000 watts. 100 watts every 25 feet of home run.

My SMA string inverter cost ~ $1,200 for 8 kW so about 15¢ a watt. AND I get an (admittedly modest, but still very useful) grid-down solution for free.

Each solution has trade-offs. Anybody who says one or the other is always the right answer is missing information or is pushing an agenda.

---
addendum: 10 awg looks too small for 40 Amps. What is awg of your wires after the strings are combined ?
 
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