Where would the Powerwall go? (Circuit Diagram)

[Blup85]

Hello,
Looking for some expert or informed advice.
I have an interesting power distribution system at my house. I have a 400 main panel that splits to a 200 amp to feed the majority of the house circuits, a shop subpanel that connects my solar arrays and a pool house sub panel (see picture)
My primary goal is to power my main home circuits for battery back-up, and peak demand pricing since I'm on PGE EV rate schedule (crazy expensive during 2-9pm!).
So, would the powerwall feed a sub-set of circuits on by 200 amp sub panel or would it connect directly to my main panel?

Also, if I decided to just feed a sub-set of circuits on my 200 amp sub panel, and used the powerwall to hedge peak pricing during peak times, wouldn't I still be pumping power to the grid from my solar arrays since its not fed thru the powerwall?

Feel free to plug in the powerwall where you see fit.

 

[GenSao]

There are several options, but 1st question, how many Powerwalls do you want installed? Do you just want back up power to plugs and outlets as originally indicated (1 PW at 30A or Less)? Or include the AC and most major appliances (2-3 PW at 60A-90A)? Do you want to 100% capture your peak solar production? If so, 3 PW is likely needed (5 KW x 3 = 15 KW PW Charge capacity > 10 KW + 2.8 KW = 12.8 KW Solar).

Other questions:
How much power (In KWH) do you use at the PG&E Peak Period at night? It does not make economic sense to over size the system.
Do you just want just the house backed up or the entire system?
What is the rated breaker/wiring between your 100 Amp Shop Panel and 400 Amp Main Panel? How long is the run?
How many spare circuit breakers are in the 100 Amp Shop and 400 Amp Main Panel?
Load calculations will be needed for each part of the system.
What is the total Amp Rating of your solar?

Some notes:
There is approx. 1 KWH/day cost for each Powerwall to run/condition.
Energy Gateway will likely be installed near you 400A panel
Tesla prefers to tie the Batteries as close to the solar breakers.
You'll likely need an extra Panel or Two depending on configuration.

For simplicity of wiring and usability, I think you'll need three PW units. Batteries and solar connected to a new 150-200A panel next to the Shop Panel. A new 100-150A line to the 400 Main Panel. Power from the outside may have to be derated to 300A breaker, a Bigger Main Panel, or a separate panel for may be needed for the power inputs adjacent to the 400A Panel.

 

[MP3Mike]

More than likely they would put the Energy gateway between your 400A panel and your 200A panel. (Sine you want to backup the 200A panel.) The Powerwall(s) would then be connected to your 200A panel. (Unless you put a panel inbetween so that you only backed up a portion of your circuits.)

The Powerwall(s) could still soak up your solar even if they are in a different panel, the only drawback would be that if there was a power outage your solar would go off-line. (The solar would need to be on the same side of the energy gateway as the Powerwall(s) if you want the solar to stay up when the grid goes down.)

 

[mongo]

@Blup85

Gateway is 200A , so before the house panel is the only existing spot available. Is it a detached shop? How much tear up are you willing to do? You could go all out with solar + PW(s) + critical loads on a new panel. Tesla sets limits on how much load is on the PW panel based on number of units, so a new subpanel may be needed regardless.

Other thought: can you swap the shop and HPWC connections? That would put the solar into the house panel with the PWs and remove the EV load from the backed up section.

 

[miimura]

The problem I see with your current setup is that there are important circuits spread across every single panel except maybe the poolhouse. You definitely want the PowerWalls, solar, well, and many of the household circuits behind the gateway so that they can run during an outage.

 

[mongo]

The problem I see with your current setup is that there are important circuits spread across every single panel except maybe the poolhouse. You definitely want the PowerWalls, solar, well, and many of the household circuits behind the gateway so that they can run during an outage.

Good catch, I missed the well.
Running a circuit from the house 200 back to the pump would solve that problem.

OP: what is the physical layout?

 

[Blup85]

Good catch, I missed the well.
Running a circuit from the house 200 back to the pump would solve that problem.

OP: what is the physical layout?

Shop is 80ft away on a 100 amp feed detached from the house

200amp house sub is on the inside of the attached garage 3 bays over from where the 400amp main is located, so running a circuit from the main to house sub is doable, but would be a pain.

I don't care about the pool sub panel, priority would be well and house main sub panel.

Is the gateway just a disconnect? Or does it measure load to regulate how much the PW discharges behind the gateway?
If that's the case, you could put the PW just about anywhere.
I was hoping to just run two powerwalls, but not sure i can run my 200 amp sub off 2 PW.

Thanks for all the input, I'm starting to get an idea how these work

 

[Blup85]

@Blup85

Gateway is 200A , so before the house panel is the only existing spot available. Is it a detached shop? How much tear up are you willing to do? You could go all out with solar + PW(s) + critical loads on a new panel. Tesla sets limits on how much load is on the PW panel based on number of units, so a new subpanel may be needed regardless.

Other thought: can you swap the shop and HPWC connections? That would put the solar into the house panel with the PWs and remove the EV load from the backed up section.

I can move the hpwc to the main 400 without much problem.
Do you mean put the shop on my 200 amp sub panel? Not really, unless a put another load center between the 400 and 200

 

[miimura]

Given that the Main and the 200A sub are close to each other, you can rearrange the loads.
1. Move the HPWC to the main (to open up capacity in the 200A sub)
2. Move the Well to the 200A sub (so it can be backed up)
3. Move the Shop panel's feed to the 200A sub (so solar can charge PWs when grid is down)
4. Move other non-essential 240V loads from 200A sub to Main. (free up more capacity in the 200A sub)
5. Install the Gateway between the Main and 200A sub
6. Install the PowerWall's circuits in the 200A sub.

The only remaining problem is that you have 12.8kW of solar which exceeds the 10kW charging capacity of two PowerWalls. If the PowerWall could interoperate with the solar to do elegant proportional curtailment, it would not be a problem.

 

[arnolddeleon]

Given that the Main and the 200A sub are close to each other, you can rearrange the loads.
1. Move the HPWC to the main (to open up capacity in the 200A sub)
2. Move the Well to the 200A sub (so it can be backed up)
3. Move the Shop panel's feed to the 200A sub (so solar can charge PWs when grid is down)
4. Move other non-essential 240V loads from 200A sub to Main. (free up more capacity in the 200A sub)
5. Install the Gateway between the Main and 200A sub
6. Install the PowerWall's circuits in the 200A sub.

The only remaining problem is that you have 12.8kW of solar which exceeds the 10kW charging capacity of two PowerWalls. If the PowerWall could interoperate with the solar to do elegant proportional curtailment, it would not be a problem.

I suspect Tesla will want to install a "generation" panel. Backfeed limits will likely prevent the PW from being installed in the 200A sub unless the feed is reduced. My PW are on twin 30A breakers so for two it will be 60A toal and I believe the backfeed limit is 20% so 40A unless the load panel is one that was designed for backfeed.

The gateway can feed two panels. In my case it feeds my main load panel and the generation panel.

Tesla wants to measure your solar output so it can have the PW follow/charge accordingly. IIRC someone had an install the required some additional work for this

If you don't have an order with Tesla already and you are looking for incentives like SGIP you will want at least 3 Powerwalls and go for the large scale storage path. I believe Tesla installed systems are fully subscribed for the rebates already. It wouldn't be surprising if the 3 with rebates was going to be cheaper than 2 without. OTOH if you end with on two I suspect the fact that your solar exceeds the Powerwall's ability to soak all the power at peak will not be a problem in practice. Reason #1, there are likely to be loads so the peak power won't be available for the Powerwalls. #2 systems rarely produce peak power and even if they did it's for short period of time.

I just 2 Powerwalls installed, less than a week ago. I have 10.9 kW + 2.4 kW of solar. Tesla installed a new 200A main panel which is designed to feed another panel (no loads in it). That service feeds the 200A gateway. My gateway feeds a 200A main load center which in turn feeds an 90A subpanel. Also connected to the gateway is 200A generation panel. That has my 2 PV systems plus the two Powerwalls.

arnold

 

[mandoskippy]

So the energy gateway is 200amp only? I have a similar setup where I have a 325 amp main breaker, and then a 150amp breaker to one house, and a 125 amp service to a different house. The Main breaker also has a panel on it. This is where I run my inverters too, so there are no backfeed limitations on the individuals houses. I put up a small "power shed" that I intended to house the powerwalls, but now reading this, it looks like it won't matter . The gateway can't go between the main and the power company I suppose, and even if I put a big throw switch between the meter and my first box, the gateway would be limited to 200amps, am I reading that correct?

 

[mongo]

Here's a concept:
Add a 100 amp sub panel by the 400A
Hook the shop and well to it
Run a new line to the house for a non-backed up load panel (new panel could also be the backed up loads instead)
Gateway feeds from 200A breaker in main panel
One GW output goes to new 100 shop//well panel
One GW output goes to the backed up house panel.
HPWC moves to 400A panel
This setup requires one new cable from house to GW and possibly some extensions for the relocated loads (along with load calculations). I'm pretty sure there would not be any breaker derating needed for the PV since the house panel can't pull more than 200A (GW will only see > 200A draw if shop and house are both loads, in which case its upstream breaker would trip).

Variant:
You could also feed the GW output into a 200A main + feed through panel. It would hold the 100A breaker for the shop and the well breaker. House would connect to pass through lugs. Its main breaker may need derated due to the solar. Alternatively, getting a higher current panel and downsizing the main breaker is also an option. However, if the house loads match the PW output, the derated breaker should not be an issue.

 

[Blup85]

Here's a concept:
Add a 100 amp sub panel by the 400A
Hook the shop and well to it
Run a new line to the house for a non-backed up load panel (new panel could also be the backed up loads instead)
Gateway feeds from 200A breaker in main panel
One GW output goes to new 100 shop//well panel
One GW output goes to the backed up house panel.
HPWC moves to 400A panel
This setup requires one new cable from house to GW and possibly some extensions for the relocated loads (along with load calculations). I'm pretty sure there would not be any breaker derating needed for the PV since the house panel can't pull more than 200A (GW will only see > 200A draw if shop and house are both loads, in which case its upstream breaker would trip).
View attachment 274083
Variant:
You could also feed the GW output into a 200A main + feed through panel. It would hold the 100A breaker for the shop and the well breaker. House would connect to pass through lugs. Its main breaker may need derated due to the solar. Alternatively, getting a higher current panel and downsizing the main breaker is also an option. However, if the house loads match the PW output, the derated breaker should not be an issue.

Thanks @mongo. I think I'm getting the idea now. Great info. So, backup loads are not run THRU the powerwall? But rather the powerwall adjusts it output based on the load that the GW measures as demand?

 

[mongo]

Thanks @mongo. I think I'm getting the idea now. Great info. So, backup loads are not run THRU the powerwall? But rather the powerwall adjusts it output based on the load that the GW measures as demand?

You've got it, PWs connect via 30Amp breaker to the house/ load side of the GW switch. GW measures current flow through it, and PWs measure their own flow. Current Transformers are used to measure your PV output. During an outage, there will be 0 current through the GW (isolation mode), but the PWs will monitor the voltage and provide power as needed to keep it regulated. The GW controls PW charging based on total load (I believe).