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I need help deciphering Tesla diagrams

I can't tell if they currently have me set up for whole home house backup or if my a/c is excluded? Can anyone decipher this for me?
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holeydonut

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Assuming your AC breaker is being moved to the new 125 Amp sub-panel box labeled [X], your AC will be backed up.

I'm still trying to figure out how you're getting 3x Powerwalls with 125A service. PG&E would have crapped all over this design because they'd assume you'd export all solar and ESS to the grid during peak time. Lucky you're in SoCal.

PS. before you approve this design, see if they can replace the conductors with the (8) circle to #8 AWG instead of #10 AWG. @h2ofun would be pleased.
 
There is no description of what loads are moved to the backup panel (N on the diagram). Details are not needed for pulling a permit, but you are entitled to know because you are the one buying the install. The math will not change. List your breakers by Amperage and breaker size and give them a list and ask them to verify which ones.
Hopefully, @holeydonut is correct? Trust, but verify is always a good philosophy, especially when dealing with any installer and any IOU.
 

holeydonut

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Jun 27, 2020
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East Bay NorCal
There is no description of what loads are moved to the backup panel (N on the diagram). Details are not needed for pulling a permit, but you are entitled to know because you are the one buying the install. The math will not change. List your breakers by Amperage and breaker size and give them a list and ask them to verify which ones.
Hopefully, @holeydonut is correct? Trust, but verify is always a good philosophy, especially when dealing with any installer and any IOU.


Luckily, Vicki is in SCE territory. I agree, trust but verify.
 
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The panel labeled X is a 225A panel. According to the note, all loads which were in the original main service panel E, are to be relocated to X. This is a whole house backup.
@holeydonut, see the note that says "the maximum output current ... towards the main panel ... is controlled electronically". Regardless of your experience, I don't see why PG&E would object to this configuration.
 

holeydonut

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The panel labeled X is a 225A panel. According to the note, all loads which were in the original main service panel E, are to be relocated to X. This is a whole house backup.
@holeydonut, see the note that says "the maximum output current ... towards the main panel ... is controlled electronically". Regardless of your experience, I don't see why PG&E would object to this configuration.


During my crap installation, PG&E asserted the power control system of the Powerwall was only software controlled, and software can fail. So at one point in time, I had a system with only 35A of solar and 2x Powerwalls for another 40A. They ignored the PCS of the Powerwalls and declared my design would need to accommodate a PCS failure and the batteries + PV exporting in full 75A back to the MSP's busbar.

So even though Sunrun was putting a 200A main service panel, PG&E said I had to de-rate my home loads to a 125A. Because 125A going to the home + 75A coming from the generation = 200A.

Eventually Sunrun went back to the drawing board but instead of 2x Powerwalls and solar, we added a 3rd Powerwall and reconfigured everything by adding a new 200A sub-panel for whole home backup (kind of like Vicki's design). When that design was up for inspection it actually passed PG&E's check. But Sunrun had to keep their shiny new 200A MSP in place.

To avoid any doubt, I think Tesla's design for Vicki is fine. I'm glad Tesla and SCE are helping make the world a better place in SoCal. I know some people think when I explain what PG&E did that I somehow actually agree with PG&E because I attempt to rationalize things through their POV. But in reality, I don't like PG&E or their perspectives.
 
when I explain what PG&E
While I have been interested in your story of exceedingly poor treatment by PG&E, I don't think it's useful to extrapolate solely from your experience in advising others. The rules are fairly well spelled out, and designs that follow them generally don't elicit such a negative PG&E response.

Cheers, Wayne
 
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holeydonut

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While I have been interested in your story of exceedingly poor treatment by PG&E, I don't think it's useful to extrapolate solely from your experience in advising others. The rules are fairly well spelled out, and designs that follow them generally don't elicit such a negative PG&E response.

Cheers, Wayne


I'm more jealous that all ya'll have such an easy time getting your systems put in. Anyway, Vicki's design looks good yeah? Well except that conductor size for her Powerwall v2.1's.
 
The panel labeled X is a 225A panel. According to the note, all loads which were in the original main service panel E, are to be relocated to X. This is a whole house backup.
@holeydonut, see the note that says "the maximum output current ... towards the main panel ... is controlled electronically". Regardless of your experience, I don't see why PG&E would object to this configuration.
Thanks! I had the a/c replaced just so it would be compatible so that is good to hear. Tesla actually recommended a few more solar panels but that is all the roof would accommodate.
 
Well except that conductor size for her Powerwall v2.1's.
The factors that go into sizing conductors and OCPD do not include tweets. When Tesla updates their PW spec sheet with a higher inverter continuous output current, or their installation instructions to call for a larger conductor, then it will be time to expect installation practices to change.

Personally, I doubt there will be a change to existing hardware that will entail using anything bigger than #10 Cu conductors and 30A breakers for a Powerwall. My guess would be that the maximum continuous output current stays at 24A, and the most that changes is an increase in the peak power output (surge capabilities). That will help with motor (HVAC) starting, but that's about it.

Cheers, Wayne
 
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Three powerwalls are 30 amps each or 90 amps. Houses do tend to average about 70 amps, you can actually get some sort of amp meter, turn on everything in the house, and go hold it up in the main panel and see.

There are many threads on here about how two PW's (60 amps) may or may not get AC startup done. I am not aware of any AC units where people with three or more PWs had any problem.

Unless there is something special about your house, with three PWs they will go for whole home.

The rest of the calcs are highly technical which is why only electricians or electrical engineers understand them fully.

The rest of us sort of speculate.
 

h2ofun

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Aug 11, 2020
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The factors that go into sizing conductors and OCPD do not include tweets. When Tesla updates their PW spec sheet with a higher inverter continuous output current, or their installation instructions to call for a larger conductor, then it will be time to expect installation practices to change.

Personally, I doubt there will be a change to existing hardware that will entail using anything bigger than #10 Cu conductors and 30A breakers for a Powerwall. My guess would be that the maximum continuous output current stays at 24A, and the most that changes is an increase in the peak power output (surge capabilities). That will help with motor (HVAC) starting, but that's about it.

Cheers, Wayne
thats what my gut is telling me now with the data. i have less concerns. just want to know why elon said November
 

holeydonut

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I am wondering how much time exactly I should put in to trying to decipher this. (I have a hard science degree and want to take it all in but also want to trust Tesla knows what they are doing)



View attachment 657816


Tesla is just doing their diligence showing your home's expected ability to draw power falls well below the threshold of the systems being installed can handle.

So assuming your hot water heater, furnace, kitchen oven, and kitchen cooktop all use natural gas... and you have no pool pump, hot tub, EV, or grow-house, then I think what Tesla is proposing is good. I'm amazed you were able to use so much power to warrant such a large system even though your house has so many gas appliances. But if this is the system you want, it'll definitely provide you with a ton of clean energy and your home's ability to use electricity is very well protected.

By the way, You really don't need to upsize those conductors between the Powerwalls and the Tesla gateway. There's just another thread on this site where people are all excited some Tweets from Elon... and larger conductors may help in anticipation of those Tweets becoming reality.

One last thing... I guess some people on the forum (myself included) may tell you that you should consider switching some appliances to use electricity instead of natural gas first. Because trying to make changes after Tesla installs stuff may be difficult due to how they label things and other electricians often do not like to touch systems that are protected behind a whole home battery backup. In my case, trying to add an EV charger after getting solar and batteries became more of a hassle than I realized. But such decisions could set you back weeks/months on your solar and battery installation.
 
Assuming your AC breaker is being moved to the new 125 Amp sub-panel box labeled [X], your AC will be backed up.

I'm still trying to figure out how you're getting 3x Powerwalls with 125A service. PG&E would have crapped all over this design because they'd assume you'd export all solar and ESS to the grid during peak time. Lucky you're in SoCal.

PS. before you approve this design, see if they can replace the conductors with the (8) circle to #8 AWG instead of #10 AWG. @h2ofun would be pleased.
It may be because her solar is only 11.4. On my 16.32 with three PWs we had to upgrade the main panel from 150 to 200, in Los Angeles, though, not SCE.
 
Tesla is just doing their diligence showing your home's expected ability to draw power falls well below the threshold of the systems being installed can handle.

So assuming your hot water heater, furnace, kitchen oven, and kitchen cooktop all use natural gas... and you have no pool pump, hot tub, EV, or grow-house, then I think what Tesla is proposing is good. I'm amazed you were able to use so much power to warrant such a large system even though your house has so many gas appliances. But if this is the system you want, it'll definitely provide you with a ton of clean energy and your home's ability to use electricity is very well protected.

By the way, You really don't need to upsize those conductors between the Powerwalls and the Tesla gateway. There's just another thread on this site where people are all excited some Tweets from Elon... and larger conductors may help in anticipation of those Tweets becoming reality.

One last thing... I guess some people on the forum (myself included) may tell you that you should consider switching some appliances to use electricity instead of natural gas first. Because trying to make changes after Tesla installs stuff may be difficult due to how they label things and other electricians often do not like to touch systems that are protected behind a whole home battery backup. In my case, trying to add an EV charger after getting solar and batteries became more of a hassle than I realized. But such decisions could set you back weeks/months on your solar and battery installation.

Holydonut is exactly right. In my whole home system there is a 60 amp Tesla vehicle charger and a 60amp AC and a 60 amp jaccuzzi pump on a 150 panel. I see yours is 125, so depending on what is in the panel now adding a Tesla charger might screw up the analysis.

Obviously, the total amps of the various circuits far exceed the panel rating, but someone who knows can explain. It appears to be not just the ratings of the circuits, but some sort of assumption as to how much draw they all draw simultaneously.
 

holeydonut

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Jun 27, 2020
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East Bay NorCal
Yes, we have gas water heater, clothes dryer, furnace, kitchen oven, and kitchen cooktop. We may add a vehicle charger in the future.



Cool, good to know!

I don't know if Tesla will do it, but maybe you can get your installer to write somewhere on the line diagram that they would be ok with you adding 48 amps of continuous load in the future into the panel labeled [X] on your line diagram. Or, I guess if they're really helpful, they can say you have a Tesla EV charger in your design right now, and provision a breaker in anticipation of an EV charger.

This may make it easier for you to find an electrician later who will put a reasonable EV charger in your house since there would be everything ready for that EV charger. For example, a Tesla Gen 3 HPWC is 48A continuous (it needs a two pole 60A breaker); and could slot right in when you're ready.

Some members here are finding that Tesla's installers are putting stickers that read "do not add loads" to the new panels during their installs. Naturally such a sticker could make a future electrician think twice about adding a load. In my case I am having a tough time finding an electrician who will touch a whole home backup out of legal-fears; and I don't even have warning stickers about adding loads.
 

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