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Dual Gateway Setup - Functionality

slazinger_7

Member
Oct 7, 2020
31
4
California
@h2ofun - did you order your system directly from Tesla? If so, do you know which office is doing the install? Tesla or its subs have been out to our property 13 times now in the last 6 months and we're still not there yet (and I don't have any indication they know what the problem is or how we are going to get everything finished). If your installers happen to get it right, would you be willing to send pictures and/or any other details so we can try to replicate it on our end?

I managed to get "installer" access to our Gateways this evening, so I can see the internal CT setup. I'll need to do some further research to see if I can troubleshoot on my end (fingers crossed!). We can't wait to finish this process.
 

h2ofun

Active Member
Aug 11, 2020
2,076
322
auburn, ca
@h2ofun - did you order your system directly from Tesla? If so, do you know which office is doing the install? Tesla or its subs have been out to our property 13 times now in the last 6 months and we're still not there yet (and I don't have any indication they know what the problem is or how we are going to get everything finished). If your installers happen to get it right, would you be willing to send pictures and/or any other details so we can try to replicate it on our end?

I managed to get "installer" access to our Gateways this evening, so I can see the internal CT setup. I'll need to do some further research to see if I can troubleshoot on my end (fingers crossed!). We can't wait to finish this process.
Nope, using a 3rd party.

Sure seems simple. The grid CT's are already in the GW. Power can only flow one way. And how can one mess up a single CT on solar?

Shall see soon. I sure will be looking over their shoulder closely on this.

GW installer log in looks pretty easy. But one person posted they changed something and may now have messed up the GW, be careful
 

slazinger_7

Member
Oct 7, 2020
31
4
California
Continuing to do more troubleshooting on my end - I don't think the issue is with the incoming solar or their CTs. Sun is currently down, and I logged into each GW (both are in "Self-Powered" mode) in laptops sitting next to each other and I can see the following:

PXL_20210222_032841332.jpg


The GW on the left shows a negative kW consumption at the "Home" icon and the GW shows no power flowing through the system. The "Grid" also shows a negative value (presumably because we are exporting to the grid at present). There is also a yellow yield sign next to the negative home consumption showing the following error:

PXL_20210222_032850274.jpg


Anyone have any idea how to troubleshoot this "Load meter may be configured incorrectly" error?

In the Tesla App, the GW on the left shows:

Screenshot_20210221-193119.png


The Tesla App for the GW on the right shows:

Screenshot_20210221-193127.png


This is what I was talking about earlier, namely the excess energy being discharged by the PW behind the GW on the right (which should be shown as heading back to the grid) is going to the "Home" and being picked up by the GW on the left as "Solar" (despite the fact that there's no solar production); and the GW on the left (not the one discharging on the right) is showing the energy being returned to the grid.

I suspect this is just a software issue in the app because it doesn't know how to handle the actual underlying issue of the "Load meter" not being configured correctly.

Any thoughts on the problem and/or a fix?
 

power.saver

Supporting Member
Mar 4, 2018
506
511
Arcadia, CA
Try switching both GWs to Backup Only mode, and see if that solar flow on the first one goes away when the second one stops discharging. If so, then you have CTs and/or wiring mixed up between them, and it needs to be corrected. The negative home in the first one is due to the grid showing negative with no other source, which can't be and also points to a configuration error.
 

slazinger_7

Member
Oct 7, 2020
31
4
California
@power.saver. You mention that the "negative home in the first one is due to the grid showing negative with no other source". Both of these GWs tie into a common 400 amp sub-panel. Could it be that the GW on the left is seeing the negative going to the grid from the GW on the right (due to discharging)?

Maybe the solution is to put in two new CT's on the lines between each GW and the 400 sub-panel, so each respective GW knows how much energy is incoming and/or outgoing along that specific connection?
 

power.saver

Supporting Member
Mar 4, 2018
506
511
Arcadia, CA
Okay, this is good. It means the solar CT from GW #1 is misplaced on some wiring for GW #2. Leave them in backup and when the sun is out tomorrow, check the solar flows. You might have to turn each solar inverter off one at a time to confirm that there is no cross-feeding between the two GWs.

Yes, you would need separate CTs for each grid feed (one pair for each GW) but I would expect them to be installed already integral to the GW. It seems you now have reasonable grid->home flows (assuming 0.2kW and 0.9kW are correct right now).

The home flow is actually calculated and not measured. That was the reason I suggested you put them in Backup mode so that we could see what the measured flows (solar, grid and battery) are like with battery and solar at zero. Tomorrow you will see the solar flow and hopefully nothing on the battery which should help pinpoint where the problem is.
 

slazinger_7

Member
Oct 7, 2020
31
4
California
When I put both GWs into "Backup-Only" mode during the day, all solar from each inverter will charge the respective PWs behind each GW, and the sub-panels behind each GW are powered by the grid. The solar values through the Tesla app have been close to being accurate (each shows about 1/2 of the aggregate solar being produced by our array as reported by SolarEdge - we have two inverters, hence the 1/2 reporting on each GW). In other words, the system appears to work correctly. I'll post pictures of the power flow tomorrow morning.

FYI - this load meter issue happens in both directions. In the example above, the left GW was on Standby and the right GW was Discharging. If the left GW is Discharging and the right GW is on Standby, the issue just reverses - see below:

Screenshots.png

Yes, the "grid->home flows" of 0.2kW and 0.9kW should be correct.
 

h2ofun

Active Member
Aug 11, 2020
2,076
322
auburn, ca
When I put both GWs into "Backup-Only" mode during the day, all solar from each inverter will charge the respective PWs behind each GW, and the sub-panels behind each GW are powered by the grid. The solar values through the Tesla app have been close to being accurate (each shows about 1/2 of the aggregate solar being produced by our array as reported by SolarEdge - we have two inverters, hence the 1/2 reporting on each GW). In other words, the system appears to work correctly. I'll post pictures of the power flow tomorrow morning.

FYI - this load meter issue happens in both directions. In the example above, the left GW was on Standby and the right GW was Discharging. If the left GW is Discharging and the right GW is on Standby, the issue just reverses - see below:

View attachment 638819
Yes, the "grid->home flows" of 0.2kW and 0.9kW should be correct.
Watching closely.

Since you have two inverters, how are they connected to the internet? Wired or wirless?

How are they connected to each other? Do you have a RS485 connected between the two? Or if hardwired, a hardwire to both?
Trying to find out the pro and cons to hardwiring both vs the RS485 connection. Manual does not tell me pro and cons
 

slazinger_7

Member
Oct 7, 2020
31
4
California
Here at the readings this morning in "back-up" only mode:

Screenshot_20210222-102009.png


Screenshot_20210222-102024.png


SolarEdge app says the combined solar production for our two inverters is about 8.01 kW, so I think the aggregate solar production shown in the Tesla app (3.8 kW + 3.5 kW = 7.3 kW) (and ready by the CT's?) should be close to being accurate.

Both GWs connect to Telsa via our home WiFi and 4g cellular (both are confirmed working). No ethernet, although I could run a connection as we have a switch nearby. I don't know if Tesla hardwired each GW together.

How do you escalate this to Telsa Energy engineering?

The "electrician" at the local Tesla office in control of our project has insistent on keeping it within his control, but, accordingly to his LinkedIN profile, he only received a journeyman's electrician's certificate in 2018 and he was a "drummer" and "painter" for the prior 30+ years (I can't make this up). We've been told by several of the licensed electrician subs that he doesn't know what he's doing.

We've asked to have this project moved to a different office (including one closer to our home), but Tesla just keeps sending out the same two guys to troubleshoot. It would be great to have an actual engineer with some experience look at this.
 

slazinger_7

Member
Oct 7, 2020
31
4
California
Later this morning I turned off the first AC disconnect to try and isolate the two systems in their entirety. Doing this turned off the electricity to the sub-panels behind GW1 (house electricity turned off in certain areas), it turned off GW1, and I could hear the PW1 bank click (I'm assuming it turned off as well).

But, to my surprised, Solar 1 did not turn off - rather, it was picked up by GW2 (which was still running) and exported to the grid (I was able to confirm at our meter that we were selling electricity back to the grid). The SolarEdge app didn't see a change in production either.

I then went inside our 400 amp breaker and flipped the breaker "off" as well - my understanding from our electrical diagram is that the AC disconnect is actually downstream of the 400 amp sub-panel. My thought here is that it would de-energize everything below the breaker (and cut off any potential cross-over), including AC Disconnect 1, GW1, PWs bank 1, and incoming Solar 1.

But, again, Solar 1 was still showing on GW2 and was still being exported to the grid.

The Tesla team that came out apparently had to "split" our solar at the inverters outside into two 40 amp lines (the solar company had combined them and ran one 80 amp line to our panel), then run a new line into the house. I am wondering if that's the location of the problem - Tesla actually did not "split" the solar come out from each inverter correctly.

Although, it seems weird the GWs and app would pick up the solar correctly in some instances, but not others. Either way, it seems like something is crossed here if Solar 1 is still working despite killing AC Disconnect 1 and the breaker in the 400 amp sub-panel servicing everything on Side 1.
 

power.saver

Supporting Member
Mar 4, 2018
506
511
Arcadia, CA
Did the GW #1 show grid failure (orange X over the grid) when you opened the breaker?

It's possible the solar are somehow still combined, and that is providing a path between the two systems.
 

Vines

Active Member
Jul 20, 2018
1,870
2,185
Silicon Valley, CA
Later this morning I turned off the first AC disconnect to try and isolate the two systems in their entirety. Doing this turned off the electricity to the sub-panels behind GW1 (house electricity turned off in certain areas), it turned off GW1, and I could hear the PW1 bank click (I'm assuming it turned off as well).

But, to my surprised, Solar 1 did not turn off - rather, it was picked up by GW2 (which was still running) and exported to the grid (I was able to confirm at our meter that we were selling electricity back to the grid). The SolarEdge app didn't see a change in production either.

I then went inside our 400 amp breaker and flipped the breaker "off" as well - my understanding from our electrical diagram is that the AC disconnect is actually downstream of the 400 amp sub-panel. My thought here is that it would de-energize everything below the breaker (and cut off any potential cross-over), including AC Disconnect 1, GW1, PWs bank 1, and incoming Solar 1.

But, again, Solar 1 was still showing on GW2 and was still being exported to the grid.

The Tesla team that came out apparently had to "split" our solar at the inverters outside into two 40 amp lines (the solar company had combined them and ran one 80 amp line to our panel), then run a new line into the house. I am wondering if that's the location of the problem - Tesla actually did not "split" the solar come out from each inverter correctly.

Although, it seems weird the GWs and app would pick up the solar correctly in some instances, but not others. Either way, it seems like something is crossed here if Solar 1 is still working despite killing AC Disconnect 1 and the breaker in the 400 amp sub-panel servicing everything on Side 1.

You have found your issue, good job. Remember what I had said that all the CT's for each system must be separated. PV and PW CT and breakers for system 1 needs to be totally independent from system 2.

The installer just needs to put some more time into it. I am sure its frustrating to have to do all this yourself.
 

slazinger_7

Member
Oct 7, 2020
31
4
California
@power.saver - yes - grid failure with orange x over the grid and an orange rectangular box around the outside.

@Vines - yes, and thank you for the suggestion; one reason I decided to try cutting power to one system to see if they were truly independent (overheard Tier 2 support telling the Tesla guys on site the same thing). Seems that's not the case. I'll put this in to our contacts and see if this goes anywhere.

All very frustrating - been a long 6+ months getting to this point; we'll be ecstatic when this process is over and the system is working correctly.
 

slazinger_7

Member
Oct 7, 2020
31
4
California
@Vines - in reading through other posts, some have suggested that, while their houses have 400 amp service, the house may actually only need less than 200 amps of service, whereby it would essentially be possible to split the 400 amp service in half and place all the loads behind a single 200 amp gateway. See, e.g., this thread:

400Amp Gateway workaround

You mentioned that the "average" load cannot be larger than 200 amps, and that it is "pretty easy to do yourself as an estimate." Can you explain the process for doing so?

If our "average" loads are 200 amps or lower, it might just be easier in our case to have Tesla come back out and reconfigure the system so all four PWs are behind one GW and to combine the solar into one input (as before), as opposed to splitting everything in the current configuration that doesn't work.

The website "gensizer.assurancepower.com" has a calculator, and it says our estimated load is 202.10 amps - see attached. I'm assuming that would be with everything turned on? If so, our average load must be well below that number because we certainly don't run all the ovens/ranges/Tesla charger at the same time, as an example. Frankly, one of the ranges is in a guesthouse that's almost never used (if we had to, we could probably put it on a sub-panel that's not backed up and the above calculation would fall below 200 amps).

I'm not an electrician, so I don't know if this would and/or wouldn't work, but I'm curious if anyone has experience in this area. We're located in Napa County, California.
 

Attachments

  • Whole House Load Calculator.pdf
    342.1 KB · Views: 5

slazinger_7

Member
Oct 7, 2020
31
4
California
As an update, I made a mistake on the first calculation that our well pump was 2 hp, when it is really 1/2 hp. Making that change dropped our "amps" calculation to 198.43 per Generator Sizing Tool | Generator Sizing Calculator for Home Use and Whole House:

Capture_1.JPG


The whole document is attached. The calculations make sense to me, and I can figure out how to arrive at the 198.43 amps number.

Tesla sent over their load calculations today and their numbers are 35% higher:

Capture_2.JPG

The non-AC loads I calculated are quite close to Tesla's (assuming I move Tesla's EV charging supply up with the rest):

Mine = 65,336 VA (9,726 + 55,610)
Tesla = 67,826 VA (9,726 (B)(1) + 12,000 (B)(2) + 36,500 (B)(3) + 9,600 EV).

The main difference resides with the A/C Equipment units:

Mine = 12,418 (52 amp)
Tesla = 33,408 (139 amp) [combined 26,688 AC units + 6,720 electric furnaces]

Tesla's numbers are about 2.7x higher.

In looking at our 5 ton Heat Pump specs, the manual says the unit is configured to run at a max of about 30 amp. Assuming a 3 ton AC is about 60% that, we would be looking at another 18 amp. Assuming the window AC is about half the 3 ton AC, that's another 9 amp. So, in aggregate, the amp draw for all our AC would be about 57 amp (i.e., close to my online calculation) and nowhere near Tesla's 139 amps. Am I missing something here?

Tesla's calculations don't provide any real detail, but if they are roughly 80 amp too high in their AC calculation, then it seems likely we can put everything behind a single 200 amp gateway.

Always appreciate the thoughts/comments if someone else has been through this exercise and can confirm whether my understanding / calculations are correct/incorrect.
 

Attachments

  • Whole House Load Calculator.pdf
    453.4 KB · Views: 4

Vines

Active Member
Jul 20, 2018
1,870
2,185
Silicon Valley, CA
@Vines - in reading through other posts, some have suggested that, while their houses have 400 amp service, the house may actually only need less than 200 amps of service, whereby it would essentially be possible to split the 400 amp service in half and place all the loads behind a single 200 amp gateway. See, e.g., this thread:

400Amp Gateway workaround

You mentioned that the "average" load cannot be larger than 200 amps, and that it is "pretty easy to do yourself as an estimate." Can you explain the process for doing so?

If our "average" loads are 200 amps or lower, it might just be easier in our case to have Tesla come back out and reconfigure the system so all four PWs are behind one GW and to combine the solar into one input (as before), as opposed to splitting everything in the current configuration that doesn't work.

The website "gensizer.assurancepower.com" has a calculator, and it says our estimated load is 202.10 amps - see attached. I'm assuming that would be with everything turned on? If so, our average load must be well below that number because we certainly don't run all the ovens/ranges/Tesla charger at the same time, as an example. Frankly, one of the ranges is in a guesthouse that's almost never used (if we had to, we could probably put it on a sub-panel that's not backed up and the above calculation would fall below 200 amps).

I'm not an electrician, so I don't know if this would and/or wouldn't work, but I'm curious if anyone has experience in this area. We're located in Napa County, California.

With a calculated load of nearly 200A you are right on the edge of making this work or not working. Load calculations are what the NEC says your house uses. The average load is what you actually use, this can be reviewed by your green button 8760 data. If your history shown useage over 200A for long peaks of time this is what to look out for.

It is not required or desirable to run both heating and cooling maximums and add them. Typically you take all AC and all heating and add each together and take the higher total. Nobody really runs both together for any length of time. Tesla also isn't taking into account the AC running amps vs the breaker size, which can be oversized to handle start up surges. It looks like your estimate is more accurate.

If you do this just know that sometimes your house does draw more than 200A. When it does, you need to have battery power available, or you will trip your main breaker. Setting the GW2 with Site control at 160A will prevent your main breaker from tripping as long as there is PW energy. Set your reserve no less than 30% so you always have this power available when needed.

Just know that you definitely don't want to add much or any new loads to the backup side, or risk popping the main 200A breaker when your house runs with everything on. If you notice your Powerwalls draining below the set reserve while on grid, then reduce your usage immediately, or risk popping the main breaker. Another EV charger if added would want to be on the non-backup side most likely. Hopefully you will still have a 200A non-backed up bus with which to add future loads?
 
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Reactions: holeydonut

holeydonut

Supporting Member
Jun 27, 2020
1,235
739
East Bay NorCal
If you do this just know that sometimes your house does draw more than 200A. When it does, you need to have battery power available, or you will trip your main breaker. Setting the GW2 with Site control at 160A will prevent your main breaker from tripping as long as there is PW energy. Set your reserve no less than 30% so you always have this power available when needed.

What's the maximum combined load that the Gateway can manage? Can someone really pull 200A from the grid and get 40A from the Powerwalls/solar? The Gateway keeps chucking along?
 

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