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For folks with 2 Gateways, do things cross charge?

h2ofun

Active Member
Aug 11, 2020
3,103
678
auburn, ca
Because of my homes 400 amp service, and having 2 200 amp subpanels for my house, both having essential circuits, I am having to put 2 gateways in, and splitting the batteries.

With solar and grid up, my solar feeds either subpanel based on need.

But when I install the TEG's, and split my solar to these TEG"S, when the grid is up, will the solar on each TEG backfeed
the entire system so either bank of batteries will charge, or the solar can be used in either subpanels still?

Again just trying to make sure I am not missing something.
 

ltphoto

Member
Oct 17, 2017
14
16
Olympic Peninsula, Washington
I was headed down the road of two gateways and separating the solar systems for the same reason as you (two 200A panels). Instead we are going to reconfigure circuits to place all the most needed backup circuits on one panel, and everything else on the other. The entire system will feed into the main panel and there will be a manual switch between panels. In an outage the Powerwalls will backup the main panel automatically. If we need power on any circuits in the secondary panel, we will have to throw a manual switch. Not convenient, but also probably not ever necessary. The second panel has things like the second electric range, electric resistance heat (main heat is heat pump), shop 240V circuits and elevator. Car charging is a wall connector which will automatically cut out in an outage. I will have either 3 or 4 Powerwalls (not yet finalized) and a single gateway. Much easier to manage.
 
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Vines

Active Member
Jul 20, 2018
2,188
2,671
Silicon Valley, CA
I am pretty sure this would cause pretty large issues. You should separate both systems entirely, with no overlapping CT's.

There may be ways to make it work if you really wanted to., the much better solution imo is an automatic or manual transfer switch to backup both sides of the service from the same system.
 

h2ofun

Active Member
Aug 11, 2020
3,103
678
auburn, ca
I am pretty sure this would cause pretty large issues. You should separate both systems entirely, with no overlapping CT's.

There may be ways to make it work if you really wanted to., the much better solution imo is an automatic or manual transfer switch to backup both sides of the service from the same system.
Interesting. I had thought about the switch idea. Can you give me more ideas on issues this may cause since we are just about ready to sent to county for approval with 2 GW's.
 

Vines

Active Member
Jul 20, 2018
2,188
2,671
Silicon Valley, CA
Manual mode: Install a 2 position (generator transfer switch) such that there are 2 subfeeds to the panel normally not backed up. In addition to the subfeed from the service, add a second subfeed that connects your main backup loads subpanels. When you wish to have whole home backup, manually throw the switch. This disconnects that panel from the grid feed and energizes the panel from the other subpanel which is always backed up.

If you wanted to throw some money at it you could make it automatic, or at least done from your smartphone. I had been looking at the Span panels with the optional 200A disconnect for this application. They are expensive but 2 of them would allow you to make a user defined second connection. I am sure other products also can do this, if I did some research.
 

h2ofun

Active Member
Aug 11, 2020
3,103
678
auburn, ca
Manual mode: Install a 2 position (generator transfer switch) such that there are 2 subfeeds to the panel normally not backed up. In addition to the subfeed from the service, add a second subfeed that connects your main backup loads subpanels. When you wish to have whole home backup, manually throw the switch. This disconnects that panel from the grid feed and energizes the panel from the other subpanel which is always backed up.

If you wanted to throw some money at it you could make it automatic, or at least done from your smartphone. I had been looking at the Span panels with the optional 200A disconnect for this application. They are expensive but 2 of them would allow you to make a user defined second connection. I am sure other products also can do this, if I did some research.
Still trying to understand what problem you are saying I might have. Here is my design going to the county.
 

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Vines

Active Member
Jul 20, 2018
2,188
2,671
Silicon Valley, CA
This is a way to use 1 gateway, and keep all your PV and PW resources behind the same gateway. Your design has no problem, except those that are unavoidable due to 2 gateways.

Then when a backup event happens you can choose to switch over to whole home. This will give you potentially longer run time and no worries about balance between the 2 systems, and also gives you the biggest juice to start large loads.

For instance if you have 2 systems and 2 gateways, you are limited to the system with the least resources will cause you to lose half power first. Not to mention all the weirdness about having 2 systems on the app and the home consumption will be split.

You asked about charging the other batteries from the first system, and this is just an alternative that avoids all this complexity, though it has other trade offs.
 

h2ofun

Active Member
Aug 11, 2020
3,103
678
auburn, ca
This is a way to use 1 gateway, and keep all your PV and PW resources behind the same gateway. Your design has no problem, except those that are unavoidable due to 2 gateways.

Then when a backup event happens you can choose to switch over to whole home. This will give you potentially longer run time and no worries about balance between the 2 systems, and also gives you the biggest juice to start large loads.

For instance if you have 2 systems and 2 gateways, you are limited to the system with the least resources will cause you to lose half power first. Not to mention all the weirdness about having 2 systems on the app and the home consumption will be split.

You asked about charging the other batteries from the first system, and this is just an alternative that avoids all this complexity, though it has other trade offs.

I agree. My issue is I have must stuff in both panels, so I cannot use just one. :( You can see that from the loads on each GW in the drawing.

Oh well, now the challenge will be is who can come up with an app that combines 2 GW's into one presentation. :)

So my original question is with the grid on, and if I wire with 2 GW's, I am assume the solar will still move around the entire 2 gw setup to provide suds to whatever needs it, PW's, house, etc? This is what I hope I am not missing with how the GW's work.
 

Vines

Active Member
Jul 20, 2018
2,188
2,671
Silicon Valley, CA
Yes, the 2 gateways cannot talk to each other. All resources must be split, and loads on either system cannot be self consumed by the other system.

All CT must not overlap, no loads CT, no PV CT's can capture the same data.

Basically what would happen is that the Powerwalls would charge from the grid at the same value as the PV generation.
 
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h2ofun

Active Member
Aug 11, 2020
3,103
678
auburn, ca
Yes, the 2 gateways cannot talk to each other. All resources must be split, and loads on either system cannot be self consumed by the other system.

All CT must not overlap, no loads CT, no PV CT's can capture the same data.

Basically what would happen is that the Powerwalls would charge from the grid at the same value as the PV generation.
Makes sense. So in my case, best way to look at it is this is basically two different homes. They both do their thing, and excess solar from both get pushed back to PGE where the meter sees the differences. Yep way more complicated than one would want.

I assume PW's never charge from grid other than SW mode?

I still am asking why with ER for SGIP who want the batteries used to reduce load on the grid will not allow me to grid charge when I do not have enough solar. I have nothing to lose with asking various folks. Just because someone else has not been successful does not mean I could not. But, not counting on it. :)
 

wwhitney

Active Member
Nov 2, 2017
1,015
1,381
Berkeley, CA
I agree. My issue is I have must stuff in both panels, so I cannot use just one.
Can you clarify a couple things for me:

- Are the existing transfer switches for the generator automatic or manual?
- You're generator is 22 kW, so that's 92A @ 240V. What is the load calculation for the loads in the panels supplied by the generator?
- What is the load calculation for the whole house? Is it above 200A?

Cheers, Wayne
 

RKCRLR

Member
Apr 13, 2020
514
214
Garden Valley, CA
I still am asking why with ER for SGIP who want the batteries used to reduce load on the grid will not allow me to grid charge when I do not have enough solar. I have nothing to lose with asking various folks. Just because someone else has not been successful does not mean I could not. But, not counting on it. :)
I'll follow your lead.
 

h2ofun

Active Member
Aug 11, 2020
3,103
678
auburn, ca
Can you clarify a couple things for me:

- Are the existing transfer switches for the generator automatic or manual?
- You're generator is 22 kW, so that's 92A @ 240V. What is the load calculation for the loads in the panels supplied by the generator?
- What is the load calculation for the whole house? Is it above 200A?

Cheers, Wayne
The 2 transfer switches for the generator are automatic

I do not remember the load calculations the contractor did for the generator. I know we put the delay modules on everything 30 amps and over.

My issue is even if the load calculation is under 200A, because of how where the loads are in the subpanels, there is no way to change the wiring. The panel in my garage has all my heat pumps for both the garage living space and the house space. The house subpanel has all the normal house stuff minus the heating/air.

So if I have a power outage, and want heat/air and house stuff, I have to have both subpanels backed up. One reason I put the 2 ATS in for the generator.

I am all ears, is there some other way I could be doing this with my limitations. If I were starting the house over, then yep, I would wire one panel essential and one non essential. But in my case they both are essential so I assume no one I could use just one GW?
 

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