Dual Gateway Setup - Functionality

[slazinger_7]

I won't go into too many details re the background, but we have had A LOT of problems with this install over the last year, including 12 visits by Tesla and/or its sub-contractors in the last 7 months.

System Setup:

We have a 400 amp service outside that feeds a 400 amp sub-panel in our basement. To get a whole home backup, my understanding is that Tesla needed to split that 400 amp sub-panel into two 200 amp sub-panels, each with its own gateway to function correctly. We have two Powerwalls behind each gateway (four powerwalls total). We also have two solar arrays (each with its own inverter - two total), and Tesla was supposed to connect one inverter behind each gateway over the weekend.

From a graphical perspective, my understanding is that our system looks something like this:

|--200 amp sub-panel_1<-->Gateway_1<--->PV Inverter_1 / Powerwall Bank_1
400 amp service<--->400 amp sub-panel
|--200 amp sub-panel_2<-->Gateway_2<--->PV Inverter_2 / Powerwall Bank_2


I'm curious if others have this setup and how their system performs. Offhand, I'm not sure ours is functioning correctly, and I will try to explain below:

In the app, Gateway_1 and Gateway_2 are on different screens, and each have the option to be set to run as (a) Backup-Only; (b) Self-Powered; or (c) Advanced.

Backup-only:

When both Gateways are in this setting, the "Power Flow" is:

- Gateway_1 shows Solar to Powerwall; and Grid to Home.
- Gateway_2 shows Solar to Powerwall; and Grid to Home

In other words, the solar is powering the Powerwalls and the Grid is powering the house. This was expected.

Self-Powered:

When both Gateways are in this setting, only one Powerwall Bank will charge at a time (despite each being connected to a PV inverter), and the second bank will discharge to charge the first. Our "Power Flow" looked something like this:

- Gateway_1 shows Solar (7.8 kW) to Powerwall (6.1 kW); and Solar (7.8 kW) to Grid (1.7 kW)
- Gateway_2 shows Solar (4.0 kW), Powerwall (4.1 kW), and Grid (0.3 kW) to Home (5.9 kW)

The house energy consumption behind Sub-panel_1 is about 1.2 kW.
The house energy consumption behind Sub-Panel_2 is about 0.9 kW.

Each inverter should be producing about 4.0 kW (or about 8.0 kW in aggregate), so Gateway_1 is showing too much Solar production; and the "house" was certainly NOT consuming 5.9 kW.

On paper, it looks like Powerwall Bank 2 is discharging to "Home" and that is being picked up by Gateway_1 as additional "Solar". The net at our meter is actually correct, we were sending 1.4 kW back (Gateway_1 is sending 1.7 kW to the grid and Gateway_2 is pulling 0.3 kW from the grid, for a net of 1.4 kW).

No clue why this is happening, but it doesn't seem correct.

****NOTE - my numbers may not be exactly right as they were fluctuating and I had to move between two screens to capture, but hopefully this will provide some context. If we get a good solar day tomorrow, I'll see if I can run two smartphone screens simultaneously to get an accurate real-time reading and update my thread.

Advanced (Balanced):

When both Gateways are in this setting, only one Powerwall Bank will charge at a time (despite each being connected to a PV inverter) and the second remains in standby. Around Noon today, our "Power Flow" looked like this:

- Gateway_1 shows Solar (7.8 kW) to Powerwall (4.1 kW); and Solar (7.8 kW) to Grid (3.8 kW)
- Gateway_2 shows Solar (4.0 kW) to Home (5.9 kW); and Grid (0.3 kW) to Home (5.9 kW)

The house energy consumption behind Sub-panel_1 is about 1.2 kW.
The house energy consumption behind Sub-Panel_2 is about 0.9 kW.

Each inverter should be producing about 4.0 kW (or about 8.0 kW in aggregate).

We are on a TOU plan where our peak-time is from 4-9 p.m.

If our solar system was producing about 8 kW at Noon, 4.1 kW was basically going to charge Powerwall Bank 1, 2.1 kW was charging the house, and the remaining 1.8 kW was being sent back to the grid. This was surprising given that we were basically selling energy back to the grid during off-peak hours (when energy is the cheapest). Why was the system not putting more into charging Powerwall Bank 1 or charging Powerwall Bank 2?

FYI - around 2 p.m. when our solar system was generating 12-13 kW, we were sending back 5-6 kW while only one battery charged. This was a lot of wasted energy being sold back to the grid during non-peak time.

We started the day with Powerwall Bank 1 at 32% and Powerwall Bank 2 at 35%. Bank 2 charged to about 78%, then the system changed over for some reason and charged Bank 1 to about 75%. If the Gateways would have been charging the Powerwalls instead of sending energy back to the grid during off-peak (see above), both banks would have charged to 100%.

Once we hit 4 p.m. (peak time), Bank 1 discharged down to 35%, and then Bank 2 also discharged down to 35% - this was expected. But, the total amount of energy discharged during this time was only 78% to 35% and 75% to 35% because the Gateways were selling energy back to the grid during off-peak earlier in the day, as mentioned above.

****NOTE - again, my numbers may not be exactly right. I will try to gather better data in the coming days and update.

This seems completely off and defeats the purpose of having the TOU setting. I would be better off getting up in the morning, turning on "back-up only", and then manually switching to TOU at 4 p.m. to get the desired charge/discharge cycle for the day.

I've read that the Advanced setting can take some time to figure out and will adjust to home energy usage as time goes on. Note that our batteries were hooked up about a month ago and Tesla got around to hooking up the solar about 5 weeks later.

Final Thoughts

I get the feeling that Telsa wired the system incorrectly because it looks like one gateway might be back-feeding to the other gateway and producing inaccurate readings for Solar generation and Home energy usage.

As a result, it doesn't appear that the systems are completely isolated, which could be a good thing during an outage as energy could be moved from one bank to another in an outage to keep all our lights on.

I'm not sure if this is how the system is supposed to be operating, so I thought I'd see if anyone else ended up in a similar complicated situation.

 

[h2ofun]

My system will be wired just about like yours. Interested in the comments

 

[h2ofun]

I won't go into too many details re the background, but we have had A LOT of problems with this install over the last year, including 12 visits by Tesla and/or its sub-contractors in the last 7 months.

System Setup:

We have a 400 amp service outside that feeds a 400 amp sub-panel in our basement. To get a whole home backup, my understanding is that Tesla needed to split that 400 amp sub-panel into two 200 amp sub-panels, each with its own gateway to function correctly. We have two Powerwalls behind each gateway (four powerwalls total). We also have two solar arrays (each with its own inverter - two total), and Tesla was supposed to connect one inverter behind each gateway over the weekend.

From a graphical perspective, my understanding is that our system looks something like this:

|--200 amp sub-panel_1<-->Gateway_1<--->PV Inverter_1 / Powerwall Bank_1
400 amp service<--->400 amp sub-panel
|--200 amp sub-panel_2<-->Gateway_2<--->PV Inverter_2 / Powerwall Bank_2


I'm curious if others have this setup and how their system performs. Offhand, I'm not sure ours is functioning correctly, and I will try to explain below:

In the app, Gateway_1 and Gateway_2 are on different screens, and each have the option to be set to run as (a) Backup-Only; (b) Self-Powered; or (c) Advanced.

Backup-only:

When both Gateways are in this setting, the "Power Flow" is:

- Gateway_1 shows Solar to Powerwall; and Grid to Home.
- Gateway_2 shows Solar to Powerwall; and Grid to Home

In other words, the solar is powering the Powerwalls and the Grid is powering the house. This was expected.

Self-Powered:

When both Gateways are in this setting, only one Powerwall Bank will charge at a time (despite each being connected to a PV inverter), and the second bank will discharge to charge the first. Our "Power Flow" looked something like this:

- Gateway_1 shows Solar (7.8 kW) to Powerwall (6.1 kW); and Solar (7.8 kW) to Grid (1.7 kW)
- Gateway_2 shows Solar (4.0 kW), Powerwall (4.1 kW), and Grid (0.3 kW) to Home (5.9 kW)

The house energy consumption behind Sub-panel_1 is about 1.2 kW.
The house energy consumption behind Sub-Panel_2 is about 0.9 kW.

Each inverter should be producing about 4.0 kW (or about 8.0 kW in aggregate), so Gateway_1 is showing too much Solar production; and the "house" was certainly NOT consuming 5.9 kW.

On paper, it looks like Powerwall Bank 2 is discharging to "Home" and that is being picked up by Gateway_1 as additional "Solar". The net at our meter is actually correct, we were sending 1.4 kW back (Gateway_1 is sending 1.7 kW to the grid and Gateway_2 is pulling 0.3 kW from the grid, for a net of 1.4 kW).

No clue why this is happening, but it doesn't seem correct.

****NOTE - my numbers may not be exactly right as they were fluctuating and I had to move between two screens to capture, but hopefully this will provide some context. If we get a good solar day tomorrow, I'll see if I can run two smartphone screens simultaneously to get an accurate real-time reading and update my thread.

Advanced (Balanced):

When both Gateways are in this setting, only one Powerwall Bank will charge at a time (despite each being connected to a PV inverter) and the second remains in standby. Around Noon today, our "Power Flow" looked like this:

- Gateway_1 shows Solar (7.8 kW) to Powerwall (4.1 kW); and Solar (7.8 kW) to Grid (3.8 kW)
- Gateway_2 shows Solar (4.0 kW) to Home (5.9 kW); and Grid (0.3 kW) to Home (5.9 kW)

The house energy consumption behind Sub-panel_1 is about 1.2 kW.
The house energy consumption behind Sub-Panel_2 is about 0.9 kW.

Each inverter should be producing about 4.0 kW (or about 8.0 kW in aggregate).

We are on a TOU plan where our peak-time is from 4-9 p.m.

If our solar system was producing about 8 kW at Noon, 4.1 kW was basically going to charge Powerwall Bank 1, 2.1 kW was charging the house, and the remaining 1.8 kW was being sent back to the grid. This was surprising given that we were basically selling energy back to the grid during off-peak hours (when energy is the cheapest). Why was the system not putting more into charging Powerwall Bank 1 or charging Powerwall Bank 2?

FYI - around 2 p.m. when our solar system was generating 12-13 kW, we were sending back 5-6 kW while only one battery charged. This was a lot of wasted energy being sold back to the grid during non-peak time.

We started the day with Powerwall Bank 1 at 32% and Powerwall Bank 2 at 35%. Bank 2 charged to about 78%, then the system changed over for some reason and charged Bank 1 to about 75%. If the Gateways would have been charging the Powerwalls instead of sending energy back to the grid during off-peak (see above), both banks would have charged to 100%.

Once we hit 4 p.m. (peak time), Bank 1 discharged down to 35%, and then Bank 2 also discharged down to 35% - this was expected. But, the total amount of energy discharged during this time was only 78% to 35% and 75% to 35% because the Gateways were selling energy back to the grid during off-peak earlier in the day, as mentioned above.

****NOTE - again, my numbers may not be exactly right. I will try to gather better data in the coming days and update.

This seems completely off and defeats the purpose of having the TOU setting. I would be better off getting up in the morning, turning on "back-up only", and then manually switching to TOU at 4 p.m. to get the desired charge/discharge cycle for the day.

I've read that the Advanced setting can take some time to figure out and will adjust to home energy usage as time goes on. Note that our batteries were hooked up about a month ago and Tesla got around to hooking up the solar about 5 weeks later.

Final Thoughts

I get the feeling that Telsa wired the system incorrectly because it looks like one gateway might be back-feeding to the other gateway and producing inaccurate readings for Solar generation and Home energy usage.

As a result, it doesn't appear that the systems are completely isolated, which could be a good thing during an outage as energy could be moved from one bank to another in an outage to keep all our lights on.

I'm not sure if this is how the system is supposed to be operating, so I thought I'd see if anyone else ended up in a similar complicated situation.

Got a wiring diagram you can post

 

[h2ofun]

My system will be wired just about like yours. Interested in the comments

My assumption is during a power outage, each GW is isolated since there is no path to backfeed if done right.

Here is my current drawing. How does this compare to your setup? So see no part if wired like this if power goes out units can backfeed each other.

 

[Vines]

Likely the issue is CT placement.

If any of the CT from system 1 are other than in the gateway 1 or downstream of it toward the loads and powerwalls, you will have this issue. In other words you likely wont have any CT in your Main service.

Do you have CT in your main service? Are any of the PV CT assigned to GW1 also captured by GW2?

 

[h2ofun]

Likely the issue is CT placement.

If any of the CT from system 1 are other than in the gateway 1 or downstream of it toward the loads and powerwalls, you will have this issue. In other words you likely wont have any CT in your Main service.

Do you have CT in your main service? Are any of the PV CT assigned to GW1 also captured by GW2?

why do these ct's seem to have issues being installed correctly?

 

[slazinger_7]

Attached are the wiring diagrams.

When you mention "CT", that's a "current transformer"? I don't know for sure, but I don't think we have a CT in our main service panel - the only thing I can see is a "Service Disconnect" switch.

How do I check to see if any of the PV CT assigned to GW1 is also captured by GW2?

 

[h2ofun]

Attached are the wiring diagrams.

When you mention "CT", that's a "current transformer"? I don't know for sure, but I don't think we have a CT in our main service panel - the only thing I can see is a "Service Disconnect" switch.

How do I check to see if any of the PV CT assigned to GW1 is also captured by GW2?

Your wiring seems to make sense. But as Vines as asked, where did they put the CT's? I believe you should have 2 sets per GW? It would be great to mark those on your drawings. I plan to do the same if and when I get installed. I sure would not expect my setup to work as you are describing.

Since the GW's I believe can be looked at like they are on two different houses, I assume the issue is where did they wire them. In the install settings, I would assume you can only assign a CT that is wired to that GW.

Sure seems a pain to have to look at different app screens for this stuff. So 2 for the GW's. I guess 2 for the inverters? Oh well.

 

[Vines]

Slazinger it all looks ok from those plans, except the CT (current transformers, or meters) aren't shown.

They look like a plastic doughnut around the main wires of the PV, main feeds, or other loads. You would have to pull off the deadfronts of the main service panel and the gateway and take pictures to really know what's up with the meters. Take pictures of the insides if you are comfortable with taking off the covers.

Also the issue could be within the programming of one of the CT Meter locations, or its orientation. There's many ways to screw up the CT's, including just putting them in flipped.

 

[slazinger_7]

Vines - thanks for the responses. I'll take a look at pulling the deadfronts off the panels tomorrow to see if I can find the CTs. In the meantime, I've added some additional information that will probably clarify the problem, so maybe I can make my search more specific.

I ran some tests tonight after the batteries were fully charged and the problem became a bit more obvious since there was no solar production:

Bank 1 (standby)
- Solar 9.2 kW (Tesla app identified significant solar production on this bank, despite it being dark)
- Grid -9.2 kW (sending to the grid)
- Powerwall = 0.0 kW (standby)
- Home = 0.0 kW

Bank 2 (discharging)
- Solar = 0.0 kW (no sun, no power)
- Grid = 0.0 kW (nothing to/from the "grid" on this bank)
- Powerwall = 9.9 kW (discharging at about a max rate)
- Home = 10.2 kW (Aggregate home consumption at this time was about 2.2 kW)

When one bank of Powerwalls discharges, a portion goes to power the home and the rest is seen by the other gateway as "solar" production and is exported to the grid.

All actual home consumption (about 1.2 kW on the breakers behind GW1 and about 0.9 kW behind GW2) is shown being consumed all through GW2.

Very odd - I hope it's a simple fix related to the CTs. Might be back to the daunting task of getting Tesla back out to look at the system again.

 

[Vines]

@slazinger_7 Do both apps show the whole home consumption when no solar or Powerwall is generating or discharging?

 

[slazinger_7]

No - each app will show its respective consumption.

For example, yesterday morning, I turned both gateways into "Backup-Only" mode and we had the following readings:

Bank 1 (charging)
- Solar 3.6 kW (all solar production was going to charge the battery in bank 1 - see same # below)
- Grid 1.0 kW (drawing from the grid to power the breakers on Bank 1 sub-panel)
- Powerwall = 3.6 kW (charging from the solar production)
- Home = 1.0 kW

Bank 2 (also charging)
- Solar 3.6 kW (all solar production was going to charge the battery in bank 2)
- Grid 0.4 kW (drawing from the grid to power the breakers on Bank 2 sub-panel)
- Powerwall = 3.6 kW (charging from the solar production)
- Home = 0.4 kW

SolarEdge app said the combined solar production was about 6.99 kW, which seems about right.

 

[h2ofun]

No - each app will show its respective consumption.

For example, yesterday morning, I turned both gateways into "Backup-Only" mode and we had the following readings:

Bank 1 (charging)
- Solar 3.6 kW (all solar production was going to charge the battery in bank 1 - see same # below)
- Grid 1.0 kW (drawing from the grid to power the breakers on Bank 1 sub-panel)
- Powerwall = 3.6 kW (charging from the solar production)
- Home = 1.0 kW

Bank 2 (also charging)
- Solar 3.6 kW (all solar production was going to charge the battery in bank 2)
- Grid 0.4 kW (drawing from the grid to power the breakers on Bank 2 sub-panel)
- Powerwall = 3.6 kW (charging from the solar production)
- Home = 0.4 kW

SolarEdge app said the combined solar production was about 6.99 kW, which seems about right.

i assume you have 2 inverters. if so how is the se app showing both?

 

[slazinger_7]

Yes - two SE solar inverters. I think the SE app just aggregates the production reported by each inverter into a single amount/graph accessible by the SE app.

 

[h2ofun]

Yes - two SE solar inverters. I think the SE app just aggregates the production reported by each inverter into a single amount/graph accessible by the SE app.

To do this, seems it has to be setup since technically these inverters could be in 2 different homes. Just the pits they did not design
a 400 amp gateway. Oh well.

 

[Vines]

The reason why this is so hard to diagnose is there are both physical and electronic things to check. Hopefully your installer is helping you out and making this right.

As long as all the CT are correctly faced, and none of the CT from system 1 capture any of the load or generation of system 2 and vice versa, the CT are setup correctly. I still suspect this CT location, facing and electronic setting to not be correct somewhere between the 2 systems.

 

[slazinger_7]

@h2ofun - yes, I think SE has the capability of aggregating more than one inverter per property. It's actually quite nice. On the layout page, I can see both arrays, the individual production for each inverter, each panel, and their individual production. Kudos to SolarEdge - great product.

@Vines - Tesla was our installer; we didn't use a certified third party. I won't go into the details, but our installation experience has been absolutely abysmal. The installers on Saturday said they'd be back on Tuesday, and no one showed up. I've emailed/called our contact in Vegas all week with no response. It will probably take a couple weeks to get a response, which is why our installation is still ongoing 5 months after the initial scheduled install date last fall.

If it is difficult to troubleshoot, I'm not sure the Tesla office responsible for our install will have enough experience to get this right. Time will tell.

On hold with the 800 number now to see if we can get someone different. She immediately recognized that the solar shouldn't be reading double on one gateway.

 

[slazinger_7]

Telsa sent the same crew out to troubleshoot the issue with our Powerwall install, and they don't seem to understand the issue. When I talked to them this morning about a potential "CT" issue, their only response was that they are "factory" units and don't need to be changed. I think they missed the point that they could be installed in the wrong spot, backwards, or missing some.

Anyway, they pulled the panel covers off and I grabbed a couple pictures - see attached.

1_Sub-Panel (top left in Electrical Load Center picture)
1_Gateway (bottom left in Electrical Load Center picture)
2_Sub-Panel (top right in Electrical Load Center picture)
2_Gateway (bottom right in Electrical Load Center picture)

In 1_Gateway, it looks like there is one CT along the black wire into the 100 amp breaker (second from the top).

In 2_Gateway, it looks like there is one CT along the black wire going into the 30 amp breaker (fourth from the top).

I believe that the 100 amp breaker pair at the top of both gateways is for the sub-panels, the 40 amp breaker (1_Gateway) and 30 amp breaker (2_Gateway) is respectively for the Powerwalls, and the 30/30 amp and 40/40 amp breaker pairs at the bottom of each gateway are for the solar.

Any thoughts?

Any help would be greatly appreciated (hopefully we can get this fixed while they are on-site today).

 

[slazinger_7]

So Tesla service came out on Thursday ALL DAY and apparently checked all the lines, replaced and checked the CT's and did a software update, but nothing changed with respect to the functionality of the system. I overheard Tier 2 tell the installers they had a crossed wire somewhere, but the installers were adamant after apparently spending a few more hours checking everything again that all was installed correctly.

If my understanding is correct, each Telsa GW is basically the gatekeeper and controls the incoming electrical energy from the solar, regulates charging/discharging of the PWs, and makes routing decisions to ensure there is enough electrical energy being supplied to the respective sub-panel behind the GW.

If this understanding is correct, then when in Back-Up only mode, it seems that the GW operates a first gate so that incoming solar energy is only routed to the Powerwall for charging. At the same time, the GW operates a second gate allowing incoming grid energy to power the sub-panel.

When the battery reaches 100%, the GW operates the first gate to close off routing to the Powerwall (so it doesn't charge) and redirects the solar to the sub-panel. If there's insufficient energy to power the sub-panel, the GW allows additional grid energy to supplement. If there's too much solar, the excess energy travels through the sub-panel unconsumed and heads back to the GW, and the GW sends that excess electrically back to the "grid" - the first destination in our case is the 400 amp sub-panel (which connects to our main service panel). When both GWs are in back-up only mode, and solar is producing more electricity than needed by the sub-panels behind each gateway, the 400 amp subpanel sees a surplus of incoming electricity that is sent back to the grid. All good.

Although, when both are placed into "self-powered" mode, one PW bank is always discharging and the other is either in standby (if full or no solar) or charging if below 100% (and there's solar production). When this happens, it almost seems that the unused energy sent back to GW1 is routed to the 400 amp subpanel, and then makes a jump to GW2 (which thinks it is additional incoming solar) and GW2 routes this energy to the GW2 sub-panel where a portion is consumed, and the excess then makes its way back to GW2, which then sends it back to the 400 amp subpanel, except this time the energy actually makes its way back to the grid.

GW2 operates a gate to direct any incoming solar from inverter 2 directly into the PW2 or, if full, that solar energy is routed to sub-panel 2 and the aggregate unconsumed electricity (from GW1 and solar from GW2) is sent back to the grid.

I hope this makes sense. Any thoughts?

 

[h2ofun]

So Tesla service came out on Thursday ALL DAY and apparently checked all the lines, replaced and checked the CT's and did a software update, but nothing changed with respect to the functionality of the system. I overheard Tier 2 tell the installers they had a crossed wire somewhere, but the installers were adamant after apparently spending a few more hours checking everything again that all was installed correctly.

If my understanding is correct, each Telsa GW is basically the gatekeeper and controls the incoming electrical energy from the solar, regulates charging/discharging of the PWs, and makes routing decisions to ensure there is enough electrical energy being supplied to the respective sub-panel behind the GW.

If this understanding is correct, then when in Back-Up only mode, it seems that the GW operates a first gate so that incoming solar energy is only routed to the Powerwall for charging. At the same time, the GW operates a second gate allowing incoming grid energy to power the sub-panel.

When the battery reaches 100%, the GW operates the first gate to close off routing to the Powerwall (so it doesn't charge) and redirects the solar to the sub-panel. If there's insufficient energy to power the sub-panel, the GW allows additional grid energy to supplement. If there's too much solar, the excess energy travels through the sub-panel unconsumed and heads back to the GW, and the GW sends that excess electrically back to the "grid" - the first destination in our case is the 400 amp sub-panel (which connects to our main service panel). When both GWs are in back-up only mode, and solar is producing more electricity than needed by the sub-panels behind each gateway, the 400 amp subpanel sees a surplus of incoming electricity that is sent back to the grid. All good.

Although, when both are placed into "self-powered" mode, one PW bank is always discharging and the other is either in standby (if full or no solar) or charging if below 100% (and there's solar production). When this happens, it almost seems that the unused energy sent back to GW1 is routed to the 400 amp subpanel, and then makes a jump to GW2 (which thinks it is additional incoming solar) and GW2 routes this energy to the GW2 sub-panel where a portion is consumed, and the excess then makes its way back to GW2, which then sends it back to the 400 amp subpanel, except this time the energy actually makes its way back to the grid.

GW2 operates a gate to direct any incoming solar from inverter 2 directly into the PW2 or, if full, that solar energy is routed to sub-panel 2 and the aggregate unconsumed electricity (from GW1 and solar from GW2) is sent back to the grid.

I hope this makes sense. Any thoughts?

This is what I am expecting in my two GW install in a few weeks. Shall see since so few seem to have installed multiple GW's, which is the best way to go