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Question about 120 percent NEC rule with Tesla Gateway 2

holeydonut

Supporting Member
Jun 27, 2020
1,852
1,231
East Bay NorCal
Lol this stuff is so complicated. The most important lesson I've learned in all of this is that it's very likely the solar companies are selling some poorly conceived systems on customers that don't even know it. Only an expert in the field would know what to do/tweak/influence/etc to get the "right" system as opposed to a "working" system.

Looking back at all the quotes I've received, I can attest the system I would have "cookie cutter out of the box" would be massively sub-optimal. From the way the racking goes up on the roof to all this electrical engineering. I guess there's a reason Tesla told me to pound sand and wouldn't sell to me haha. And of course PG&E would probably still try to block it...
 

Vines

Active Member
Jul 20, 2018
1,913
2,247
Silicon Valley, CA
Wow, just wow. I have to really wonder who at PGE got a bee in their bonnet. I have tried to decipher your SLD by your description, since I feel bad how sideways this went for you. I hope that this way you can get what you paid for eventually.

Basically imo PG&E is just being obstinate, and the text they are asking you to put there is just to give you a win without really losing anything on either side.

If getting the SLD signed off by a PE, and adding some text to the plans will let them go forward with the service upgrade, then its the easy path forward, for a few hundred bucks and a couple days.

Its actually good you got involved as this could go round and round with PGE otherwise, this is actually a win wrapped in a pain in the ass. Sunrun should have no issues getting a PE to stamp it, and off you go. However, what is your time worth, did you save the money you wanted to?

As to the wiring and SLD, sounds like you have that figured, I concur that 2/0 Cu is appropriate from MSP to GW, then 3/0 to the external 200A panel with 200A main breaker. In the example I am showing I would use #1 Cu to the 125A Main Breaker in the non backup loads subpanel.

Here's my interpretation of your case.

holey SLD1.jpg
 

wwhitney

Member
Nov 2, 2017
900
1,188
Berkeley, CA
Aren't Powerwalls occasionally a load when they go into stormwatch mode?

Also, I think the 125A backup load subpanel disqualifies the "Entire load associated with a dwelling"
You're thinking of (2017) 310.15(B)(7)(1) or (2). Subsection (3) says no feeder in the dwelling has to be larger than the the size computed in section (1) or (2).

Cheers, Wayne
 

holeydonut

Supporting Member
Jun 27, 2020
1,852
1,231
East Bay NorCal
Wow, just wow. I have to really wonder who at PGE got a bee in their bonnet. I have tried to decipher your SLD by your description, since I feel bad how sideways this went for you. I hope that this way you can get what you paid for eventually.

Basically imo PG&E is just being obstinate, and the text they are asking you to put there is just to give you a win without really losing anything on either side.

If getting the SLD signed off by a PE, and adding some text to the plans will let them go forward with the service upgrade, then its the easy path forward, for a few hundred bucks and a couple days.

Its actually good you got involved as this could go round and round with PGE otherwise, this is actually a win wrapped in a pain in the ass. Sunrun should have no issues getting a PE to stamp it, and off you go. However, what is your time worth, did you save the money you wanted to?

As to the wiring and SLD, sounds like you have that figured, I concur that 2/0 Cu is appropriate from MSP to GW, then 3/0 to the external 200A panel with 200A main breaker. In the example I am showing I would use #1 Cu to the 125A Main Breaker in the non backup loads subpanel.

Here's my interpretation of your case.

View attachment 609169


Thanks Vines! I think my initial thread (when I first joined TMC) threw you off a bit. Sunrun ended up realizing they couldn't do the partial home backup in an intelligent way... so they shifted to whole home backup.

I just have to sign something that says if the AC's don't work when on Battery+PV only, it's not on them. This approach also keeps me from having to explain to my wife why she can't run the AC's if PG&E isn't available.

This slightly modified diagram is more along the lines of what I think they're doing. The "Backup Loads" now has the same 90 A and 70 A breakers that used to be in my old main service panel.

I'm going to be their second customer under the large-scale SGIP. I'm scared.


upload_2020-11-16_21-24-32.png





PS: If you're wondering why each of the solar branches is 20 A but the combined is 35A... it's because that's what they're gonna do and I get to live with it. I asked for a 40 A PV subfeed but they said no, I only need 35 A.
 
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holeydonut

Supporting Member
Jun 27, 2020
1,852
1,231
East Bay NorCal
However, what is your time worth, did you save the money you wanted to?


Lol definitely regret this whole process. I think this is what PG&E wants though... for people to hear the horror story and then not convert to green energy.

I just wish your company would actually do solar. I couldn't find a company that would do the PV portion with the stand-off racking method (with top and bottom flashing) instead of tile hooks. That literally was the primary reason I went with Sunrun since they were the only one willing to entertain that racking in my area. The company you recommended for PV won't come out this far.

The Sunpower installer wanted way too much and could only do 1 PW. A couple of local PV + ESS installers could only get 1 PW, or only did LG Chem.

I never talked to Semper... I wonder if they'd have been different.

Anyway, at this point, I wouldn't even know who to go to for a one-stop shop that wouldn't just push a cookie cutter design.

And I can't imagine why PG&E is being such a-holes. Haha j/k. PG&E sucks... they shouldn't be expected to behave in a good way.
 

Vines

Active Member
Jul 20, 2018
1,913
2,247
Silicon Valley, CA
Lol definitely regret this whole process. I think this is what PG&E wants though... for people to hear the horror story and then not convert to green energy.

I just wish your company would actually do solar. I couldn't find a company that would do the PV portion with the stand-off racking method (with top and bottom flashing) instead of tile hooks. That literally was the primary reason I went with Sunrun since they were the only one willing to entertain that racking in my area. The company you recommended for PV won't come out this far.

The Sunpower installer wanted way too much and could only do 1 PW. A couple of local PV + ESS installers could only get 1 PW, or only did LG Chem.

I never talked to Semper... I wonder if they'd have been different.

Anyway, at this point, I wouldn't even know who to go to for a one-stop shop that wouldn't just push a cookie cutter design.

And I can't imagine why PG&E is being such a-holes. Haha j/k. PG&E sucks... they shouldn't be expected to behave in a good way.

The company I work for has started moving away from curved tile roofs, unless its new construction. If you got rejected for a tile roof, that's a recent development. Unfortunately we are so slammed that we aren't taking every job so some jobs management has decided to decline tile for the moment until we catch up a bit.

Sucks man but you are pretty close to the end now of the painful journey.
 

holeydonut

Supporting Member
Jun 27, 2020
1,852
1,231
East Bay NorCal
The company I work for has started moving away from curved tile roofs, unless its new construction. If you got rejected for a tile roof, that's a recent development. Unfortunately we are so slammed that we aren't taking every job so some jobs management has decided to decline tile for the moment until we catch up a bit.

Sucks man but you are pretty close to the end now of the painful journey.


Yeah, tile roofs are all the rage out here. Tile hooks seem to have helped with install speed, so it bumped up the margin for the installers. But I've heard some pretty gnarly stories about the tile hooks from my roofer.

I also feel like I've been hit with way too many roadblocks, bumps, screw ups, etc in the planning aspects of my install. Even the Sunrun local manager of the Walnut Creek office says he's never seen a customer get hit with all of these problems.

It's clear to me that Sunrun isn't ready to sell these Powerwalls. And I don't even think they're equipped to sell solar since PG&E has workers wanting to send a message to Sunrun by blocking my install.
 

Vines

Active Member
Jul 20, 2018
1,913
2,247
Silicon Valley, CA
Tile hooks are not one of our choices, we always use a post and lead flashing, and have a roofer come out and do that work. There are other products that can be used but we only want double flashed tile attachments.
 
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holeydonut

Supporting Member
Jun 27, 2020
1,852
1,231
East Bay NorCal
Tile hooks are not one of our choices, we always use a post and lead flashing, and have a roofer come out and do that work. There are other products that can be used but we only want double flashed tile attachments.


Lol that explains why you guys stopped doing racking on tile roofs haha. Costs more money to do it that way, and the margins are so thin now due to Tesla's undercutting :(
 
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holeydonut

Supporting Member
Jun 27, 2020
1,852
1,231
East Bay NorCal
@Vines , @wwhitney ... after i survive this clean energy clusterffffff and COVID, I owe you both a drink... Can you let me know if you believe the attached modified form of Vines' diagram will work?

I'm proposing to put my home loads on the Gateway 2's internal panelboard and using the sub-panel exclusively for generation and battery.

I pinged my Sunrun PM (I know, I'm a terrible person bugging folks during a holiday), and he said he wouldn't allow Wayne's proposal of using one of those quad breakers to sneak the 3x powerwalls plus solar on the TEG2 internal panelboard.

So I think the change to Vines' drawing is necessary since I need a single big-a$$ disconnect lever outside my house that actually lets the firefighter shut down the Solar and ESS. I cannot believe Sunrun's original line diagram basically left this thing out.

I feel like the internal Panelboard can handle my current home 90A and 70A loads, but Tesla has never drawn up any of their diagrams this way. They always show the internal panelboard being used for generation/Powerwall. So it's not clear to me if things could be flipped on its head like this.

I also don't know if I need a single OCPD is required to protect the internal panelboard now that it has the backup loads.

Couple of important subtleties...
A) the "main size" breaker on the TEG 2 is still empty since I'm not using the TEG2 as service equipment
B) the HOM2040L225PRB sub panel is rated for 225 Amps, but I'm going to cap it with a 125 A OCPD



upload_2020-11-27_22-29-15.png
 
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wwhitney

Member
Nov 2, 2017
900
1,188
Berkeley, CA
I pinged my Sunrun PM (I know, I'm a terrible person bugging folks during a holiday), and he said he wouldn't allow Wayne's proposal of using one of those quad breakers to sneak the 3x powerwalls plus solar on the TEG2 internal panelboard.
That seems short sighted, since the Powerwall 2 with Backup Gateway 2 installation manual says on page 28: "The Internal Panelboard is 200 A-rated and supports 6x 1” breaker spaces (12 circuits) using Eaton BR branch circuit breakers up to 125 A maximum." So Tesla clearly allows the use of quad and tandem breakers, per the "12 circuits" comment.

So I think the change to Vines' drawing is necessary since I need a single big-a$$ disconnect lever outside my house that actually lets the firefighter shut down the Solar and ESS.
I haven't followed the other thread closely enough--has someone from your jurisdiction actually told you need that, or are you just anticipating it? With the Gateway 2's internal panel used for generation via quads, you could just put the Gateway 2 outside.

Here's another option for you, if Sunrun won't budge on the quad breakers: put in a small combiner panel by the Powerwalls. The (outdoors) Gateway 2 internal panel would be your generation panel and can have (1) 90A breaker for the (3) Powerwalls, and the (2) 20A breakers for the two microinverter strings (or (1) 35A breaker if that panel shown with the (2) 20A breakers is on the roof or something).

I also don't know if I need a single OCPD is required to protect the internal panelboard now that it has the backup loads.
The relevant language is (2017) NEC 705.12(B)(2)(1)(b), which requires "An overcurrent device on the load side of the power source connection shall be rated not greater than the ampacity of the feeder." That language implies a single OCPD. But physics wise there's no reason two OCPDs whose sum is not greater than the ampacity of the feeder wouldn't do the same job.

Cheers, Wayne
 

holeydonut

Supporting Member
Jun 27, 2020
1,852
1,231
East Bay NorCal
Yeah, since I've been hit with every single BS issue on this install, I'm confident someone is going to crap all over Sunrun's line diagram as "unsafe" unless I proactively try to get out in front.

You can see here where they've diagramed their current AC Disconnect. It literally won't do anything useful in this configuration.
upload_2020-11-27_21-36-28-png.612491


I agree having the Gateway 2 outdoors with all the PV and ESS breakers should be fine. But those quad eaton 30A/30A breakers are really hard to find... and I'm not holding out hope that Sunrun has some sitting around.

So do you think that new diagram will work where I run the house loads off of the internal panelboard and use the bottom lugs to connect to a Generation panel? This way the big switch is outside and would look "normal" to an inspector who isn't aware of what a TEG2 looks like.

Sunrun's electrician is coming out on Dec 2; I don't have much time. I can always let them put in the system as they diagram and give them a "I told you so" if I get tripped up during inspection. I just don't want this dragging into 2021 due to the ITC.


Here's another option for you, if Sunrun won't budge on the quad breakers: put in a small combiner panel by the Powerwalls. The (outdoors) Gateway 2 internal panel would be your generation panel and can have (1) 90A breaker for the (3) Powerwalls, and the (2) 20A breakers for the two microinverter strings (or (1) 35A breaker if that panel shown with the (2) 20A breakers is on the roof or something).


I'll see if the installer can do this option if I can't put the home loads on the internal panelboard.

The two 20 A strings are joined into a 35A by the Enphase Combiner Box that is sitting outside on my wall. But the Enphase combiner can only combine AC PV sources, it can't be used to combine the Powerwalls :(
 
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wwhitney

Member
Nov 2, 2017
900
1,188
Berkeley, CA
So do you think that new diagram will work where I run the house loads off of the internal panelboard and use the bottom lugs to connect to a Generation panel?
From a pessimistic point of view (i.e. everyone involved is going to give you as hard a time as possible), I would say no, because the language I quoted refers to a single OCPD, not two OCPDs. And there's no way to put a main breaker on the TEG2 internal panelboard larger than 125A.

Which version Enphase Combiner Box do you have? And the Powerwalls are inside the garage, right?

Cheers, Wayne
 
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holeydonut

Supporting Member
Jun 27, 2020
1,852
1,231
East Bay NorCal
From a pessimistic point of view (i.e. everyone involved is going to give you as hard a time as possible), I would say no, because the language I quoted refers to a single OCPD, not two OCPDs. And there's no way to put a main breaker on the TEG2 internal panelboard larger than 125A.

Which version Enphase Combiner Box do you have? And the Powerwalls are inside the garage, right?

Cheers, Wayne


Gotcha, thanks Wayne! I'll see if Sunrun can make a mini generation panel then; and pipe that into a lonely 125A double-pole on the TEG2 internal panelboard (facing outdoors). This means they can abandon that big-ol-lever-switch. BTW, 125 A double-poles are amazingly hard to find as well. WTF is going on with Eaton's supply chain?

Yeah, the Powerwalls are all on my interior garage. I've already kind of door-dinged one trying to put the baby in the back of the car.

The Enphase Combiner is a 3C. The 20A inputs are two separate AC home runs coming off my roof from the microinverters. The combined current then feeds through a 35A to be mounted somewhere.

I looked into this to act as a generation panel for PV and ESS, but it won't work. The Enphase recommends 3C to have no more than 80A total of generation equipment plugged into it, and each input breaker should be 20A. The only time you should exceed 20A on each breaker is if you have an Enphase Aggregator on your roof bringing 3 strings together for one home run up to 60A. There's also a separate 10A to run the Enphase Envoy that cannot be removed. And, the whole thing seems to mess up if you put loads in there that aren't microinverter output current.
 

wwhitney

Member
Nov 2, 2017
900
1,188
Berkeley, CA
Gotcha, thanks Wayne! I'll see if Sunrun can make a mini generation panel then; and pipe that into a lonely 125A double-pole on the TEG2 internal panelboard (facing outdoors).
Generation panels don't require a main breaker. Just panels with loads on a feeder with two sources. I'd push for the 30/30 quad solution, otherwise I like a 90A (or 100A or 125A) and a 35A in the TEG2 internal generation panel.

WTF is going on with Eaton's supply chain?
Presumably COVID ripples.

Cheers, Wayne
 
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holeydonut

Supporting Member
Jun 27, 2020
1,852
1,231
East Bay NorCal
Generation panels don't require a main breaker. Just panels with loads on a feeder with two sources. I'd push for the 30/30 quad solution, otherwise I like a 90A (or 100A or 125A) and a 35A in the TEG2 internal generation panel.


Presumably COVID ripples.

Cheers, Wayne



Thanks Wayne, I think I have enough options to present to Sunrun.


Option 1: Ask them to make a generation panel that feeds the TEG2 internal panelboard. But if they use a panel like this; why wouldn't they just put the 3x 30A and 1x 35A double poles into it? Then I could plug this generation panel directly to the bottom lugs on the TEG2. I'm trying to understand the benefit of putting only the Powerwalls into a sub panel and then running the 35A separately onto the TEG2 internal panelboard.

A generation panel with everything in it will also provide the benefit of piping through a big-lever-switch outside of my house. This way the inspector sees the big lever (can't claim glove-hands!) instead of BR style breakers.


Option 2: Try to get them to just use a Quad 30A alongside a 35A double pole on the TEG2 internal panelboard. This would need to be mounted outdoors and safety placards describe the PV/ESS disconnect as all the breakers on the TEG2 internal panelboard.


Option 3: let Sunrun do whatever is currently drawn up even though it's weird. This setup has the AC disconnect outside of the gateway so it really makes no sense.
 
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