Beautiful 6 Powerwall Installation

[Vines]

PG&D Disconnect for what? The PowerWall? I had to have them installed for my SMA inverters.

I was hoping to install two PowerWalls for whole house backup, but I'm just not seeing how they're going to integrate it into my panel. Still, I'd like to be as prepared as possible when Semper comes out for my site assessment on Thursday.

I'd love to hear that I could add a 200A master breaker in the lower left corner but if that were possible then I'm sure the box would've come that way instead of having four 100A breakers in the center of the right half. Perhaps they can take advantage of the fact that the meter lugs are connected to those four main breakers by four wires that could presumably be somehow re-routed out to the gateway (if that's allowed) and back into the main panel to feed the four 100A breakers that make up the 200A panel.

Even if I make it past all of that, then I'm guessing the 100A breakers will likely have to be replaced with something smaller like 70A to accommodate the 120% rule and the fact that I have 15A and 20A solar breakers, plus the two new 30A breakers for the PowerWalls.

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Whole home backup will not completely work, but whole home plus the car charger off backup likely work.

Land only a 100A breaker to the GW2, and a 60A remains for the car charger. If you really need car charging while off grid, I recommend a 20A 240V outlet installed separately.

See the top left in bold of the top sticker of your service panel. 100A max branch circuit breaker. 200A cannot be safely taken from this panel bus per its listing.

I recommend you run your load calculations for all the other loads in that panel, except car charger. If they total less than 100A then maybe you just run your whole house on a 100A branch circuit breaker, which leads to the Gateway 2. If you really need charging off grid, you can look at that. Its possible that the car charger set to a lower setting along with all your other loads is less than 100A calculated.

The GW2 also has some functionality in it (Site and Conductor Limits) to prevent that 100A breaker from popping if you temporarily draw more than the 100A breaker can take.

I recommend relocate all the PV, along with the new ESS in the GW2 internal 200A subpanel. Then install a small subpanel to relocate those loads from the MSP to be backed up.

Feeding that MSP bus wont happen easily, and quite difficult to make code complaint. There are non obvious problems to doing this and really you don't have that much load that it makes any sense. I'll guess its about 76A calculated load on your main panel from the alternate method load calculation (220.83.A)

 

[lemketron]

I don't know if it's permissible to have a line leave the meter panel without circuit protection, even if that protection is provided as soon as it enters another box, like the Gateway.

I don't either but I kinda thought that was why the gateway is "service entrance rated" and it seems that it can take a 200A "main" service disconnect breaker...

 

[Vines]

You can make a Gateway a Service Entrance panel. The proper way to do that is install a meter socket only, that then feeds the Main breaker in the Gateway 2. The service panel is where you install the main bonding jumper, but what you propose often leads to a ground loop.

I do not recommend trying what you are proposing with this panel. Read up on the main bonding jumper and see if it can even be removed in your panel.

Service equipment is rated to do what it does, and has specific rules about it. If there was a fire and you had a panel rigged as described without a UL relisting it would automatically be the fault of that improper connection. Relisting it is more expensive than the solution I have proposed.

 

[lemketron]

Whole home backup will not completely work, but whole home plus the car charger off backup likely work.

Land only a 100A breaker to the GW2, and a 60A remains for the car charger. If you really need car charging while off grid, I recommend a 20A 240V outlet installed separately.

See the top left in bold of the top sticker of your service panel. 100A max branch circuit breaker. 200A cannot be safely taken from this panel bus per its listing.

I recommend you run your load calculations for all the other loads in that panel, except car charger. If they total less than 100A then maybe you just run your whole house on a 100A branch circuit breaker, which leads to the Gateway 2. If you really need charging off grid, you can look at that. Its possible that the car charger set to a lower setting along with all your other loads is less than 100A calculated.

My whole house ran on a 100A panel before I added the second solar inverter. I upgraded to 200A because of the 120% rule as I needed 35A (15A + 20A) of PV breakers. It wouldn't be a big deal to separate the EV charger (that just feeds a 14-50 in the garage and has since been replaced by a 50A breaker) and have that not be backed up. In fact, I have a 40A sub-panel in the garage already which I could use for off-grid EV charging if it were absolutely needed but I don't have enough solar to be wasting much of it on the car if we're in an extended outage.

That said, I'm not as thrilled about moving the loads off of the current panel to a new panel. Are you suggesting that or suggesting that the PW can back-feed the main panel through a 100A breaker?

The GW2 also has some functionality in it (Site and Conductor Limits) to prevent that 100A breaker from popping if you temporarily draw more than the 100A breaker can take.

I saw that... Was just reading the Powerwall Installation Manual which is fascinating reading! I had no idea the gateway was so flexible.

I recommend relocate all the PV, along with the new ESS in the GW2 internal 200A subpanel. Then install a small subpanel to relocate those loads from the MSP to be backed up.

I suspect that would be the easy answer in most cases but I really don't want to have to choose which circuits to back up, and feel like with two PWs I shouldn't have to. I have good information on my consumption patterns, and can't think of many circuits I would NOT want backed up aside from maybe the dryer and A/C; I did request the slow-start option for A/C as it could be challenging to get wife approval without also backing up A/C.

Feeding that MSP bus wont happen easily, and quite difficult to make code complaint. There are non obvious problems to doing this and really you don't have that much load that it makes any sense. I'll guess its about 76A calculated load on your main panel from the alternate method load calculation (220.83.A)

As mentioned the original panel was 100A service and we had everything we have now except the second solar inverter. Big loads are just EV, A/C, oven, and dryer. So yes, I don't have that much load, but due to the location of this panel on the back corner of my house, in stucco, with circuits coming in from top and bottom (and having already dealt with opening and closing that wall from the inside and outside) I wasn't sure there was an easy way to relocate 24 circuits anywhere else where we could legally install another sub-panel. At the least we'd have to splice and extend everything to get to another box. Perhaps we could put a surface mount load center to the right of the current panel and put that downstream of the Gateway. I'm not actually sure where the gateway will go either for that matter.

Are you saying that we can't simply go from meter lugs to the Gateway, and then back into the four 100A breakers in the panel? Is it a physical issue of the two to four conductors? What if I just fed a single pair of those four 100A breakers from the gateway? What is the non-obvious problem?

Here is a wider look at the wall the MSP is on (the house is a tri-level so there is a partially below-grade floor and an upper floor at this end of the house), and a look at the inverter hardware right around the corner to the left of the MSP. I figured the gateway and PowerWalls would go to the left of the left-most inverter. Connecting the inverters to the gateway won't be a problem if needed (if it's over there). Not sure if it's allowable to install a new load center (or anything) to the right of the MSP which would be above that lower window...

In any case, thanks for the great tips and helping me understand the issues and possibilities!

 

[Vines]

You cannot go from meter to gateway to 200A breaker without relisting that panel through UL field evaluation services.

I estimate you can take all your loads from the MSP and put them on the backup system, except the car charger. No need to pick and choose. Choose all loads except the car charger.

No issue with putting a small 125A panel with main breaker just to the right of your MSP, as long as the gas meter is not right there. Not sure where your gas meter is, if any.

I'd let your installer help you make these choices from here on. The only way you get a UL listed panel with 200A backed up is to replace the panel with a new one or go through UL field evaluation services.

 

[lemketron]

You cannot go from meter to gateway to 200A breaker without relisting that panel through UL field evaluation services.

Understood. Really unfortunate since the fact that the meter lugs are connected via wires to the 4x100A breakers to the bus would make it really easy to do that, but I get that it's a UL listing thing. :-(

I estimate you can take all your loads from the MSP and put them on the backup system, except the car charger. No need to pick and choose. Choose all loads except the car charger.

I guess that means my 24-circuit MSP would be left with just the 4x100A main breakers, the existing 2x60A breakers for the EV charger, and a new 2x100A (maximum allowed in this panel, I believe?) breaker for the circuit to the gateway. I assume the PowerWalls and solar inverters would be connected directly into the gateway (and should be easy as that stuff will all be on the side of the house).

No issue with putting a small 125A panel with main breaker just to the right of your MSP, as long as the gas meter is not right there. Not sure where your gas meter is, if any.

So there would be a 125A (backed up power) connection from the gateway (which is presumably situated around the corner near the inverters and the PowerWalls) to a new 125A load center panel.

I kinda wish I had a nice conduit running from the MSP to the inverter area, but we just ran a pair of 12ga romex in the wall from the MSP to the junction box between the two inverters. Never thought I might need something capable of sending 100A (or 125A) over and back. So while I eliminated a bunch of ugly conduits that were added over the years by putting everything in the walls (including up to the attic), it seems like there's going to be a big conduit (or two) added, going around the corner and around the downspout as well, unless we want to tear open the inside drywall yet again. With the 12ga Romex it was a PITA to go through the corner framing so we may have to live with the exterior conduit; I'll see what they suggest.

I'm not sure how "small" that panel will be (as it still needs to host the remaining 20-ish circuits) to the right of the current MSP. I suppose it could also be surface mounted as opposed to flush mounted if that makes things any easier but all 20 of those circuits would need to be (extended and) relocated from the current MSP.

I'd let your installer help you make these choices from here on. The only way you get a UL listed panel with 200A backed up is to replace the panel with a new one or go through UL field evaluation services.

I really appreciate the advice, and explanation (since my engineering mind always likes to know what is possible, and what isn't, and why) which should prove helpful in the site assessment tomorrow. Thanks again!

 

[CrazyRabbit]

Sorry I never saw your question. The installation was covered by Tesla through the referral program including a new breaker panel to backup the whole house The install process went smoothly except I had to make arrangements to have the batteries charged while waiting for utility inspection. Since the post I added a 3rd Powerwall (see photo with the 3 Powerwalls over my Model S. Also see photo of my setup. The boxes from left to right are 1. breaker box for Powerwalls, 2. Utility meter to measure Powerwall charging/discharging, 3. Shut off for Powerwalls, 4. Backup Gateway, 5. Sprinkler Box, 6. Utility Service Entrance with main meter, 7. Breaker Panel for whole house, 8. Main Power Disconnect.
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So if someone throws your main power disconnect and locks it along with your solar disconnect you will be running on batteries until the batteries drain and when the grid comes back up you will still be without power. Why did you let them do that?

 

[miimura]

@lemketron You can think about your existing center-fed panel as two 100A panels collapsed into one box. The EV circuit can remain in the top section and a new 100A breaker will feed the Gateway from the bottom section. I don't think you need to do anything with the wiring between the inverters and the main panel. I think you will just have the Gateway 2 and a new Backup Loads panel (200A bus?) next to the main panel if it fits. Everything will just be extended into the new panel or gateway through a gutter box or something similar.

 

[lemketron]

That's what I had thought too, but after reading several TMC threads that mention that exact same panel, I'm now more convinced that the bus bar is a single 200A bar (not two separate 100A bars), though the prongs are certified only for 100A meaning you can only attach 100A breakers -- this is why there are two sets of 100A breakers. I'm still not entirely convinced but can't test it without throwing (and/or pulling) the breakers.

In any case it doesn't really matter... I'll leave the 60A EV circuit, add a 100A circuit to feed the gateway, and the gateway will feed a 125A subpanel which should go to the right of the current panel to receive all of the other circuits. Everything was previously in a 100A panel so I don't anticipate any problems load-wise. Most of the circuits consume less than 1 kwh/day, and the only 240V loads we have are the oven, dryer, A/C, and EV. There's also a 40A subpanel in the garage but it's all 120V loads (except I used to have an L6-20 connected there for the LEAF charger and will probably put a 14-30 on it for garage charging and/or emergency charging from the PW if ever needed.

 

[Vines]

That's what I had thought too, but after reading several TMC threads that mention that exact same panel, I'm now more convinced that the bus bar is a single 200A bar (not two separate 100A bars), though the prongs are certified only for 100A meaning you can only attach 100A breakers.

Exactly, my post about individual busbars was incorrect. unfortunately I cant correct it.

Some older panels of a different model/manufacturer were indeed 2 separate busbars but not this one. I have pulled one apart just to make sure.

 

[kevincday]

It has an 18 kW PV system attached to it, and it will be used heavily for load shifting, not just backup power. Though with 6 PW the backup system is very robust. There are quite a few loads in this house, pools, hot tub ect. Its a large beautiful power hungry home with a 600A switchboard.

@Vines, thanks for the posts here. I have a new home with a 600A panel and I had the builder run the cable from there to my powerwall location. However in the end the electrician said the powerwalls were not compatible with a 600A system... and I cannot have the powerwall unless I just power a single subpanel.

I've been desperate for the past year to find someone that did a 600A system.... yours is the first I have seen. Any tricks / approaches I can share with my electrician? I would be extremely grateful![/QUOTE]

 

[Krash]

I expect Vines will say that the Powerwall will work behind a 600A main but that the Tesla automatic transfer switch will only switch 200A, so in your case a sub panel sized set of breakers.

 

[Janus]

I expect Vines will say that the Powerwall will work behind a 600A main but that the Tesla automatic transfer switch will only switch 200A, so in your case a sub panel sized set of breakers.

Yeah, you probably will end up with 3 independent 200A systems. Other with 400A house ended up splitting their 400A service into two 200A subpanels. Then each of those 200A subpanels has their own gateway, powerwalls, and solar. The only question would be if Tesla support 3 gateways on one account.

The important thing to remember; the 200A subpanels are all independent. i.e. if the PowerWall on the first panel is fully drained, there is no way to transfer/share power from a PowerWall on a different panel.

 

[Vines]

@Vines, thanks for the posts here. I have a new home with a 600A panel and I had the builder run the cable from there to my powerwall location. However in the end the electrician said the powerwalls were not compatible with a 600A system... and I cannot have the powerwall unless I just power a single subpanel.

I've been desperate for the past year to find someone that did a 600A system.... yours is the first I have seen. Any tricks / approaches I can share with my electrician? I would be extremely grateful!

We deal with 600-1000A services quite often, as we serve many large homes and mansions.

Your question is common and there's no simple answer.

Whole home backup is most difficult with larger services, so your first step is to understand your impedance. This determines how many Powerwalls you can install in total. There is no reason you cannot have 3 Gateways, and divide up your solar resources among the 3, except that each individual system may not have very many Powerwalls. Your system may not start large loads in that case. If your impedance allows only 6 Powerwalls for instance you have to divide those 6 among 3 backup systems. The app will show 3 gateways no problem but your whole home consumption will be wonky.

An alternate approach that allows you to maintain all your loads in the home, then self manage them so as to not run down your backup system gets a little more complicated. A 2 position transfer switch is the bridge turning non backup loads into backup loads. This also allows your app to function correctly, and one view shows your whole house load, using one of the larger rope CT's around your main service feed.

If you plan on a ICE generator as well then that should be considered at the same time.

 

[kevincday]

We deal with 600-1000A services quite often, as we serve many large homes and mansions.

Your question is common and there's no simple answer.

Whole home backup is most difficult with larger services, so your first step is to understand your impedance. This determines how many Powerwalls you can install in total. There is no reason you cannot have 3 Gateways, and divide up your solar resources among the 3, except that each individual system may not have very many Powerwalls. Your system may not start large loads in that case. If your impedance allows only 6 Powerwalls for instance you have to divide those 6 among 3 backup systems. The app will show 3 gateways no problem but your whole home consumption will be wonky.

An alternate approach that allows you to maintain all your loads in the home, then self manage them so as to not run down your backup system gets a little more complicated. A 2 position transfer switch is the bridge turning non backup loads into backup loads. This also allows your app to function correctly, and one view shows your whole house load, using one of the larger rope CT's around your main service feed.

If you plan on a ICE generator as well then that should be considered at the same time.

Thanks!

 

[Stealth]

Can you share photos of what the insides of these look like? I’m also interested in how the meter connects to the main power disconnect. Is the main power disconnect fed directly from the meter lugs?

I have a 200A service entrance with integrated load center and am trying to understand if the main power disconnect can be added Separate from (and external to) the box with the meter...

As requested please find photos of what the insides look like. Frist is the overall photo. Second on the left is the inside of the breaker panel for the Powerwalls, then the meter, then the shutoff (not opened), then the inside of the Gateway. The third photo shows the inside of the main entrance panel with just one 200 A breaker, then the inside of my breaker panel and the main shutoff is to the right (not open). You can see that the main entrance panel feeds the line down below my breaker panel and goes directly to the main shutoff which then feeds to the top of the Gateway. The Powerwalls feed to the left side of the Gateway. The output of the Gateway is on the right and feeds directly into my breaker panel. Hope this helps.