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'whole home backup' confusion

jgbaum

Member
Aug 25, 2021
20
11
San Diego
I recently had a system installed (16kW, 2PW+, backup gateway 2) and all of my paperwork references 'whole home backup'. Basically, they pulled all of my loads from my main panel into a subpanel connected to the gateway. The only breaker in my main panel now is a 100A going to the gateway. What's odd to me is that they had me upgrade my main panel and service (which required significant trenching and $$$) from 100A to 200A, but they're only feeding this subpanel (which is capable of 225A) with 100A. There are several new loads I'd like to add in the coming months (EV chargers, electric dryer, water heater), which my project advisor was aware of, but there doesn't seem to be the bandwidth to support these in the subpanel. Am I mistaken? Should I ask Tesla to update the wiring/breaker to 200A?

My understanding (which may be wrong!) is that in order to be powered by my PV system or PWs when the grid is out, loads would need to be in the subpanel as no electricity would flow to the main.

I've included the wiring diagram below. Any insight would be much appreciated.

Thanks!


n91ktoodr6i71.png
 
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BGbreeder

Member
Jun 19, 2020
503
302
Bay Area
If you want more loads, then yes, you will probably want to upgrade the breaker and wiring.

However, if you didn't tell Tesla that you planned more loads, and you only had a 100A of existing loads, which would seem to be the case as you need a main service panel upgrade, then that is your issue not theirs. i.e. you had (I presume) 100A of loads and they are proposing 100A of backup. Seems reasonable from here.

I would hope that if you told them there were some Tesla cars in your and their future, they would do the upgrade.

Either way, I would do it now. It will be a bigger job, and more hassle later.

All the best,

BG
 
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Vines

Active Member
Jul 20, 2018
2,192
2,685
Silicon Valley, CA
I recently had a system installed (16kW, 2PW+, backup gateway 2) and all of my paperwork references 'whole home backup'. Basically, they pulled all of my loads from my main panel into a subpanel connected to the gateway. The only breaker in my main panel now is a 100A going to the gateway. What's odd to me is that they had me upgrade my main panel and service (which required significant trenching and $$$) from 100A to 200A, but they're only feeding this subpanel (which is capable of 225A) with 100A. There are several new loads I'd like to add in the coming months (EV chargers, electric dryer, water heater), which my project advisor was aware of, but there doesn't seem to be the bandwidth to support these in the subpanel. Am I mistaken? Should I ask Tesla to update the wiring/breaker to 200A?

My understanding (which may be wrong!) is that in order to be powered by my PV system or PWs when the grid is out, loads would need to be in the subpanel as no electricity would flow to the main.

I've included the wiring diagram below. Any insight would be much appreciated.

Thanks!


n91ktoodr6i71.png

I am honestly floored that such a design passes their QA. Either that or something else is going on.

Take a picture of the sticker on the inside door of the service panel, make sure it's clear enough to read.
 
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I'm curious about this too as my plans are somewhat similar. They are using a 125A breaker from the 200A main service panel to the gateway and then from the gateway there will be two panels, one for backed up loads and the other for non-backed up loads. I assumed the 125A might be the limit for the maximum breaker size for the 200A service panel but I don't know.

My backed up panel will have a 40A, 70A, 20A DP breakers and a 15A and 20A SP breakers. The non-backed up panel will have two 60A DP breakers.
 
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Vines

Active Member
Jul 20, 2018
2,192
2,685
Silicon Valley, CA
I'm curious about this too as my plans are somewhat similar. They are using a 125A breaker from the 200A main service panel to the gateway and then from the gateway there will be two panels, one for backed up loads and the other for non-backed up loads. I assumed the 125A might be the limit for the maximum breaker size for the 200A service panel but I don't know.

My backed up panel will have a 40A, 70A, 20A DP breakers and a 15A and 20A SP breakers. The non-backed up panel will have two 60A DP breakers.
It's only an issue if you just bought a new 200A service panel, and they are only using 100A or 125A of it.

If it's your existing service panel, then this is a reasonable approach.
 
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It's only an issue if you just bought a new 200A service panel, and they are only using 100A or 125A of it.

If it's your existing service panel, then this is a reasonable approach.
Thanks Vines, and OP sorry to highjack your thread. I'll limit myself to this post.

Yes, it is existing. We upgraded it two years ago before thinking about adding solar and battery.

My only concern is that I could see scenarios where we could get awfully close to the 125A. Two EVSEs pulling 40-48A each, AC at 20A, plus other home loads including an electric oven. Not a terribly likely scenario but not impossible. I guess at that point if the 125A breaker trips, the system goes in backup mode and the EVSE would be without power since they are not backed up.
 
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Vines

Active Member
Jul 20, 2018
2,192
2,685
Silicon Valley, CA
Thanks Vines, and OP sorry to highjack your thread. I'll limit myself to this post.

Yes, it is existing. We upgraded it two years ago before thinking about adding solar and battery.

My only concern is that I could see scenarios where we could get awfully close to the 125A. Two EVSEs pulling 40-48A each, AC at 20A, plus other home loads including an electric oven. Not a terribly likely scenario but not impossible. I guess at that point if the 125A breaker trips, the system goes in backup mode and the EVSE would be without power since they are not backed up.
If your installer set it up properly it will use (EDIT) PCS settings to make up the difference with whatever PV or Powerwall power it has available.
 
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Vines

Active Member
Jul 20, 2018
2,192
2,685
Silicon Valley, CA
If your installer set it up properly it will use (EDIT) PCS settings to make up the difference with whatever PV or Powerwall power it has available.
So for instance if you draw 150A from your loads for some amount of time, your Tesla gateway would limit the draw from the 125A breaker, and supply the rest of the power from whatever other sources it has like PV or Powerwall resources.

If configured with PCS settings, those will override whatever other settings the user has control of in the app like "Backup only mode"
 
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jgbaum

Member
Aug 25, 2021
20
11
San Diego
If you want more loads, then yes, you will probably want to upgrade the breaker and wiring.

However, if you didn't tell Tesla that you planned more loads, and you only had a 100A of existing loads, which would seem to be the case as you need a main service panel upgrade, then that is your issue not theirs. i.e. you had (I presume) 100A of loads and they are proposing 100A of backup. Seems reasonable from here.

I would hope that if you told them there were some Tesla cars in your and their future, they would do the upgrade.

Either way, I would do it now. It will be a bigger job, and more hassle later.

All the best,

BG
Thanks for the feedback. I had a few discussions with my 2nd (of 3 total) project advisor and have a few emails to back that up. I will reach out again to my current advisor and see what they can do.
 
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BGbreeder

Member
Jun 19, 2020
503
302
Bay Area
Thanks for the feedback. I had a few discussions with my 2nd (of 3 total) project advisor and have a few emails to back that up. I will reach out again to my current advisor and see what they can do.
I really do,think that the correct thing to do is a 200A breaker with wiring to match. I can't think why they would do otherwise, other than to save $14.29 in breaker and wire costs.

All the best,

BG
 
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jgbaum

Member
Aug 25, 2021
20
11
San Diego
I am honestly floored that such a design passes their QA. Either that or something else is going on.

Take a picture of the sticker on the inside door of the service panel, make sure it's clear enough to read.

Here's a pic I took inside the door of the new main panel when it was installed a few months back. Unfortunately, the inspection papers are covering some of it. I can snap another pic with a better view tomorrow if the info you're looking for isn't here.

IMG_9408.jpg
 
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Vines

Active Member
Jul 20, 2018
2,192
2,685
Silicon Valley, CA
Here's a pic I took inside the door of the new main panel when it was installed a few months back. Unfortunately, the inspection papers are covering some of it. I can snap another pic with a better view tomorrow if the info you're looking for isn't here.

View attachment 701517

There is no reason I can think of except they could not find the proper 4 pole HOM2200BB, so they used a 100A instead. Breakers were very hard to find over Covid supply issues.

In effect, your service upgrade Is mostly wasted in my opinion. Your entire system is limited to 200A simply because they didn't install 200A breakers and wire.

I would have them replace those with fully rated wires and 200A breakers. The 4 pole ones are several hundred dollars and that's what you need to have this done right. https://www.amazon.com/Homeline-Circuit-Breaker-HOM2200BB-Approved/dp/B008HKAJGA

In many cases, a 100A breaker could have landed on your original panel, so if 100A is all they are giving you to the gateway, why make you upgrade the service? Likely a ball got dropped somewhere but it's a bad look.
 
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SoCal Jimmy

Active Member
Apr 24, 2016
1,353
528
Inland Empire
i had originally done a Tesla solar subscription along with my 4 referral batteries , this is similar to how they did my install.
They moved all the house loads to a subpanel and feed it from a 125a breaker. I thought that was kinda stupid since the subpanel clearly had room for expansion but their design team only takes into consideration what you have today.
When i removed the subscription and went with my own solar install, the new installer laughed at how tesla had down it and said that was wrong.
they ran a HOM2200BB breaker with 2/0 cable from the main panel to feed the sub panel(edit: i think the 220a breaker goes to the gateway2 but i don’t recall).
Everything including the car charger is now on the subpanel with the exception of the pool and spa breakers which are still on the main panel. During an outage, i don’t care if those are off. (I might move the pool over though.)
 
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My system was installed today in the same way. The permit plans show 100a feeding into the gateway and then to my whole house (which was previously on a 200a main load center). The electrician actually installed a 110a breaker to the gateway. My project advisor said its most likely because he didn't have a 100a breaker so he sized it up? Looking at a couple of my friends install in the area, they all got 125a to the gateway. I'm not sure why it can't go higher than 125 and why mine was sized at 100a.

OP, did you ever get a follow up from Tesla?
 
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Vines

Active Member
Jul 20, 2018
2,192
2,685
Silicon Valley, CA
My system was installed today in the same way. The permit plans show 100a feeding into the gateway and then to my whole house (which was previously on a 200a main load center). The electrician actually installed a 110a breaker to the gateway. My project advisor said its most likely because he didn't have a 100a breaker so he sized it up? Looking at a couple of my friends install in the area, they all got 125a to the gateway. I'm not sure why it can't go higher than 125 and why mine was sized at 100a.

OP, did you ever get a follow up from Tesla?
It's all about what your existing main panel will take. Take a picture of the sticker inside the lid of your main panel and the breakers we can see what's what.
 
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It's all about what your existing main panel will take. Take a picture of the sticker inside the lid of your main panel and the breakers we can see what's what.
This is the panel I have: Square D Homeline 200 Amp 30-Space 42-Circuit Outdoor Ring-Type Surface Mount Solar-Ready Main Breaker Plug-On Neutral CSED-SC3042M200PS - The Home Depot
It is rated for 200amp main breaker with 225 bus bar. Before the install it had 125amp breakers in there feeding to my subpanel. Now it only has one 110amp breaker to the gateway.
 
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jgbaum

Member
Aug 25, 2021
20
11
San Diego
My system was installed today in the same way. The permit plans show 100a feeding into the gateway and then to my whole house (which was previously on a 200a main load center). The electrician actually installed a 110a breaker to the gateway. My project advisor said its most likely because he didn't have a 100a breaker so he sized it up? Looking at a couple of my friends install in the area, they all got 125a to the gateway. I'm not sure why it can't go higher than 125 and why mine was sized at 100a.

OP, did you ever get a follow up from Tesla?
I haven't yet gotten a satisfactory response. The response that I did get was completely insane to me. Basically, I was told to have an electrician add all of the new circuits that I want to the existing subpanel (EV charger, electric water heater, electric dryer, etc.), then to follow up with Tesla so they can evaluate if they need to update the design. So, build then plan...ludicrous.

Luckily, my credit card payment hasn't posted yet and I was able to get my credit card company to cancel my payment to Tesla. I'm hoping that will get their attention and will let you know how it plays out.
 
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I haven't yet gotten a satisfactory response. The response that I did get was completely insane to me. Basically, I was told to have an electrician add all of the new circuits that I want to the existing subpanel (EV charger, electric water heater, electric dryer, etc.), then to follow up with Tesla so they can evaluate if they need to update the design. So, build then plan...ludicrous.

Luckily, my credit card payment hasn't posted yet and I was able to get my credit card company to cancel my payment to Tesla. I'm hoping that will get their attention and will let you know how it plays out.
I just had an install done here in SD as well. I read this and went out back to look and it turns out I am in a slightly worse situation... 90A. I had never received any diagrams or permit paperwork and wasn't really consulted when they were doing the work, and was never even shown anything before any crew left on any day. We are definitely planning on getting an EV in the not-so-distant future, and likely replacing the AC with a heat pump. Absolutely mind boggling. I have an inspection for mine tomorrow already so I am not really sure what the options are here.

Hell, I still have no idea what they actually installed on the roof and getting any answers to that is just.. not happening.

I basically just have "whatever they felt like doing" attached to my house with no paperwork to show what they actually did as things were changed on the day of install. Went from 8.77kW roof to 13.04kW for... reasons? Who knows - all I know is that the price only changed by $100 or so.

Ooooo boy this is gonna be interesting tomorrow. I guess shame on me for assuming they would install the equivalent to what I had access to in the panel already.
 
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Vines

Active Member
Jul 20, 2018
2,192
2,685
Silicon Valley, CA
Just for my understanding, can’t you get a 200A sub-feed lug kit for Homeline panels? Since you have the main isn’t that all you would need?
Subfeed kits are available but usually in a similar form factor to the 4 pole breaker.

It's sort of a grey area, but I was taught that when subfeed lugs are used they basically continue the busway. In my interpretation, you need a main breaker inside the Tesla Gateway if you use subfeed lugs in the main panel.
 
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