What wiring needed 4Powerwall in detached garage 2 back up a house located 20' away?

[khanh dam]

Location: North Carolina
Project will have
42 solar panels 315w total of 13.23kw mounted to roof of barn/garage with enphase micro inverters.
Detached Garage has 100a panel that will need to be upgraded and underground conduit that is about 20 feet long going to main meter.
House is located 20 feet away and has a 200a main panel located about 10 feet from the meter.

My question is if the Tesla power wall is in the detached garage, how can the system be wired so that the main house has back up power when the grid goes down?
Will the tesla power wall get powered from the solar panels while the grid is down? Or will the power wall slowly run out of capacity because enphase micro inverters dont' produce power when the grid is down?

[Ampster]

.............

My question is if the Tesla power wall is in the detached garage, how can the system be wired so that the main house has back up power when the grid goes down?
Will the tesla power wall get powered from the solar panels while the grid is down? Or will the power wall slowly run out of capacity because enphase micro inverters dont' produce power when the grid is down?

Tesla just announced that they are restricting Powerwall sales to projects which include a Tesla solar installation. If that is not a restriction then conceptually like all Powerwall installations, the GT solar is AC coupled to the Powerwall. Tesla has migrated to their own inverters so I do not think Enphase micros would be an option. If they are already existing, yes, they would be AC coupled to the Powerwall or Powerwalls. The best information is to configure a system on the Tesla site or go to one of the Tesla user forums where there are users who have been through the installation process. No worries about the Tesla site, they do not sell your information to anyone and they do not have enough staff to make calls unless you specifically request that they call you.

As to how the system is wired, there are a variety of options since the gateway is separate and could be configured to power an essential loads panel that would power your house. The size and number of breakers will determine how many Powerwalls will be needed if you want all of your home powered. Much of that is discussed on the user forums.

[khanh dam]

thanks found forum For Powerwall users — Tesla Forums

[PVAndy]

Location: North Carolina
Project will have
42 solar panels 315w total of 13.23kw mounted to roof of barn/garage with enphase micro inverters.
Detached Garage has 100a panel that will need to be upgraded and underground conduit that is about 20 feet long going to main meter.
House is located 20 feet away and has a 200a main panel located about 10 feet from the meter.

My question is if the Tesla power wall is in the detached garage, how can the system be wired so that the main house has back up power when the grid goes down?
Will the tesla power wall get powered from the solar panels while the grid is down? Or will the power wall slowly run out of capacity because enphase micro inverters dont' produce power when the grid is down?

You can use Powerwalls with Enphase MIcros. They will form a microgrid and keep the micros on when you loose the grid. If your load isn't high enough, Powerwalls are fully charged, and you have solar production exceeding usage, the Powerwalls will raise the microgrid frequency out of UL1741 range and the solar will shut off. It will come back on after Powerwalls are drained some. Regarding rewiring the garage, there are ways to not have to do that. Minimum of 2 Powerwalls required with your size sysetm. Each Powerwall is 30A so if combined would require #6 wire. Both house and garage can be backed up by Powerewalls

Andy

[khanh dam]

Minimum of 2 Powerwalls required with your size sysetm. Each Powerwall is 30A so if combined would require #6 wire. Both house and garage can be backed up by Powerewalls

Andy

customer can only afford one power wall, might buy a 2nd latter on. what is the best way to wire up this situation?

[Ampster]

what is the best way to wire up this situation?

.......
Let Tesla worry about that. They have done thousands of installs. Their price is the most competitive anyway.

[khanh dam]

.......
Tesla just announced that they are restricting Powerwall sales to projects which include a Tesla solar installation.

they actually still sell the batteries to other solar companies like SunRun and I'm pretty sure sunrun installs the battery and not tesla. SunRun's price is about 2x for the tesla battery vs buying direct from Tesla. But like you said I think Tesla wont' sell direct to the customer a battery alone.

[Ampster]

You and your customer could spend your time more productively thinking about which loads to back up and not worry about the topology of the wiring. Those would be the loads that are swung to the critical loads panel. For simplicity that location would most likely be near where those loads enter the panel.
The larger elements of gateway and Powerwall connection is what your customer is paying Sunrun or Tesla to do as part of the installation process. I am sure you will get a design to approve before construction starts if you want control over that element.

[PVAndy]

You and your customer could spend your time more productively thinking about which loads to back up and not worry about the topology of the wiring. Those would be the loads that are swung to the critical loads panel. For simplicity that location would most likely be near where those loads enter the panel.
The larger elements of gateway and Powerwall connection is what your customer is paying Sunrun or Tesla to do as part of the installation process. I am sure you will get a design to approve before construction starts if you want control over that element.

The reason I brought up the need for 2 Powerwalls has to do with max solar that can be connected to a Powerwall. You could split up the micros and use some to charge Powerwall during a grid outage (connect to gateway) and connect some to line side of gateway so it turns off during grid outage. We have designed several hundred Powerwall installs and had problems early on with too much solar. Tesla has revised guidance based on experince

Andy

[Ampster]

The reason I brought up the need for 2 Powerwalls has to do with max solar that can be connected to a Powerwall. .....

Yes, that is an important aspect of system design especially for AC coupled systems. I do not know if the OP has a working knowledge of those parameters. Unless he has a Tesla authorized installer like yourself providing him input the only thing he or his customer would need to worry about is what loads to put in a critical loads panel subject to the limitations that you have already discussed.

[khanh dam]

The reason I brought up the need for 2 Powerwalls has to do with max solar that can be connected to a Powerwall. You could split up the micros and use some to charge Powerwall during a grid outage (connect to gateway) and connect some to line side of gateway so it turns off during grid outage.
Andy

Thanks what does Tesla recommend 6kw of solar panels per Powerwall2 battery setup? Is what I have seen, does that seem correct?

[Ampster]

....what does Tesla recommend 6kw of solar panels per Powerwall2 battery setup?

Your question reminded me of another detail that might need clarification.
Is the maximun capacity of AC coupled solar per Powerwall based on the AC inverter capacity or the DC solar panel capacity?

[oregon_phil]

I ran the tesla quote machine on the web. For every 4.05kW DC of panels, they recommended 1 Powerwall. Looks pretty basic. Nothing is said about inverters.

[SunEagle]

I ran the tesla quote machine on the web. For every 4.05kW DC of panels, they recommended 1 Powerwall. Looks pretty basic. Nothing is said about inverters.

Is that calculation for the Powerwall or Powerwall2? I believe they are different animals.

[Ampster]

....... For every 4.05kW DC of panels, they recommended 1 Powerwall. Looks pretty basic. Nothing is said about inverters.

I can believe that as a generic recommendation for an online query. That ratio would be good for selling Powerwalls. I have seen some figures from other hybrid inverter manufacturers that distinguish between older UL 1741 AC coupled inverters and newer UL 1741SA inverters. Ultimately the Powerall is interfacing with the GT inverter on the AC bus, not the panels on the DC bus. At least that is how my Skybox defines the interface.