Installation Questions

[cr0ntab]

Hey All,

I had asked someone about how to have a few non-backed up loads (pool and ev charger) in a powerwall install and they gave me this picture, which is exactly what I'm looking for:

Imgur

Today my solar contractor upgraded the main panel. When I got home I saw this installed:

Siemens 200 Amp 24-Space 42-Circuit Flush Mount Solar Ready Meter Load Center Combination-MC2442B1200EFV - The Home Depot

From all my reading I didn't see an option for that panel to use any feed through lugs. (nor does it visibly seem like it can?)

I'm not necessarily sure the installer made a mistake, however, I have a feeling they're going move all of the circuits out of this panel and over to a new sub behind the gateway.

Then later in the installation process once we get the gateway and the rest of the powerwall gear install a 200A breaker in this panel to feed the gateway.

However, if they use a 200A breaker in the main I can't add any additional loads due to NEC 705.12.d.2.3.c

Which isn't what I want.

After doing some more research it looks like this is more inline with what I'll need:

Square D Homeline 200 Amp 8-Space 16-Circuit Outdoor Ring-Type Semi-Flush Mount Solar-Ready Main Breaker Plug-On Neutral CSED-SC816F200PF - The Home Depot

It does advertise having feed through lugs, (and you can see them in the picture) it only has 8 spaces (perfect for my pool equipment and an EV charger).

Before I bring this up to my installer I wanted to get a bit of feedback on some other installations to see if I'm misunderstanding something.

 

[GenSao]

The main panel your contractor installed should be fine for your setup. It is the feed-trough panel in Imgur. The contractor can install a 200A breaker for a 200A circuit to the Tesla gateway.

All of the backed up circuits should be moved to a new sub-panel behind the gateway. You should be fine to adding loads in the 200A sub-panel behind. For that panel you are not limited to a sum of 200A for all the breakers.

 

[wwhitney]

As to your handwritten diagram, while I agree that as shown it meets the letter of 705.12(D)(2)(3)(c), it certainly doesn't meet the spirit. That is, logically it makes no difference whether the 200A breaker feeding the Tesla gateway is in the Tesla gateway and connected to subfeed lugs in the main panel, or is in the main panel and connected to the Tesla Gateway. So the absence of language in 705.12(D)(2)(3)(c) that subfeed lugs should be counted as per the breaker protecting them is just an oversight.

I think what'd you really like is a 200A feeder from your main panel to the Tesla Gateway and downstream backed up loads, plus a splice to that feeder going to another main breaker panel for your non-backed up loads. That splice is allowed under 705.12(D)(2)(1), and it could be a tap per 705.12(D)(2)(2). I think that's the only way to do what you want without using a 400A panel.

Cheers, Wayne

 

[cr0ntab]

The main panel your contractor installed should be fine for your setup. It is the feed-trough panel in Imgur. The contractor can install a 200A breaker for a 200A circuit to the Tesla gateway.

All of the backed up circuits should be moved to a new sub-panel behind the gateway. You should be fine to adding loads in the 200A sub-panel behind. For that panel you are not limited to a sum of 200A for all the breakers.

Thanks for the reply!

I'm not concerned about adding loads to to the sub panel behind the gateway. That all makes good sense to me.

I'm concerned about adding loads (pool and ev charger) in front of the gateway. (So they aren't backed up)

As I interpret NEC 705.12.d.2.3.c if we use a 200A breaker in the main to feed the Tesla gateway I cannot add the (non backed up) pool or ev charger circuits to the main.

As to your handwritten diagram, while I agree that as shown it meets the letter of 705.12(D)(2)(3)(c), it certainly doesn't meet the spirit. That is, logically it makes no difference whether the 200A breaker feeding the Tesla gateway is in the Tesla gateway and connected to subfeed lugs in the main panel, or is in the main panel and connected to the Tesla Gateway. So the absence of language in 705.12(D)(2)(3)(c) that subfeed lugs should be counted as per the breaker protecting them is just an oversight.

I think what'd you really like is a 200A feeder from your main panel to the Tesla Gateway and downstream backed up loads, plus a splice to that feeder going to another main breaker panel for your non-backed up loads. That splice is allowed under 705.12(D)(2)(1), and it could be a tap per 705.12(D)(2)(2). I think that's the only way to do what you want without using a 400A panel.

Cheers, Wayne

Hey Wayne, thanks for the insight!

I think I follow what you're saying here.

I guess my next question would be, given the Siemens panel that they installed where would they make that tap?

The meter socket does have two lugs, but both are used for the 200A service disconnect.

I'm guessing they'd need a different type of panel to get that done?

I want to make sure I call them on this if I need to before we move too far forward. I don't want to have to re-do all of this electrical down the line. We're starting from scratch right now, might as well get it right.

 

[miimura]

Why can't you put a smaller breaker in the main panel feeding the Gateway? With the 200A main and a 150A feeding the gateway, you could add more loads in the main panel. My installation is like this. I had a 125A breaker feeding a sub-panel. This breaker was used for the grid feed on the Gateway and the sub-panel was wired to one set of load lugs on the gateway. The new generation panel was wired to the second set of load lugs on the gateway. I still have 2 50 amp EVSE circuits active in the main panel that aren't backed up. I have another 160 amps of loads in the main panel that are wired but not active.

 

[cr0ntab]

Why can't you put a smaller breaker in the main panel feeding the Gateway? With the 200A main and a 150A feeding the gateway, you could add more loads in the main panel. My installation is like this. I had a 125A breaker feeding a sub-panel. This breaker was used for the grid feed on the Gateway and the sub-panel was wired to one set of load lugs on the gateway. The new generation panel was wired to the second set of load lugs on the gateway. I still have 2 50 amp EVSE circuits active in the main panel that aren't backed up. I have another 160 amps of loads in the main panel that are wired but not active.

Well I certainly can

However, you're the first person to mention that it was an option, so I just didn't know.

As far as loads that aren't backed up, I'm looking at:

60A breaker for pool equipment
50A breaker for EVSE

My old panel had a 100A main for everything so I could certainly downsize the breaker to the gateway to leave some more head room.

I'll ask about this option as well.

Thanks guys!

 

[wwhitney]

Note that the panel you linked to is "solar ready" which means it has a 225A bus but a 200A main breaker. This arrangement allows up to 70A of backfeed under 705.12(D)(2)(3)(b). So if the installation is for 2 Powerwalls or less, and you don't have solar, you can put as many breakers for loads in that panel as you like.

Cheers, Wayne

 

[wwhitney]

I see you mentioned a solar contractor. So if the solar inverter output current is no more than 32A, and the install is one Powerwall, then that also qualifies under 705.12(D)(2)(3)(b).

For 705.12(D)(2)(3)(c), the bus rating is 225A, so you could use any combination of breakers for the Gateway and for your non-critical loads panel that add up to 225A or less.

Cheers, Wayne

 

[wwhitney]

I guess my next question would be, given the Siemens panel that they installed where would they make that tap?

In the context of the NEC the word tap refers to a specific kind of splice, where one leg has an ampacity below the rating of the breaker protecting the feeder. That leg is then limited in the length it can run, and the other end must land on a circuit breaker whose rating does not exceed the ampacity of the leg. So whether the splice is a tap or not is a separate issue.

Anyway, the idea would be to splice the feeder going from the 200A branch circuit breaker in your main panel (or from the sub feed lugs) to the lugs (or breaker) in the gateway. The easiest way to do that would be to use double lugs on either end of the feeder, if possible. Otherwise, you'd need some 3-port insulated mechanical connectors. That connection could be made in either the main panel enclosure, or the gateway enclosure (Tesla may not like that idea, although not for any good reason I'm aware of), or in an additional intermediate enclosure.

Cheers, Wayne

 

[Mickey Mouse]

I might be out of my league in this conversation but I would like to try anyway. I ordered a whole house connection for my powerwall and Tesla sent me a price quote for 2 installed with an installation price of over 3,000$ , I had a choice to order 1or2 powerwalls I elected one powerwall with a partial backup and the installation price went to 2700$, so the second powerwall is only 300$ more to install. I just install solar with enphase inverter and a new main electrical service panel ( EATON COMBINATION METER 100amps MBE1224PV100BTS), I have 4 one inch slots not used right now, please explain how Tesla plans on hooking this one powerwall about 30 feet a away , next to the solar inverter, will the installers knock a hole on the side of my main service panel or replace this service panel and that’s why the installation price is very high, I elected conduits exposed on my outside wall.

 

[SoundDaTrumpet]

Without seeing the itemized list, I was initially going to say that the installation cost includes a main panel upgrade. Past TMC postings show main panel upgrades typically start at $2500 and up; however you mention "partial backup" so with all the 20A or less circuits being backed up, it seems to verify news that Tesla Energy has issued a new pricing matrix. (As evidence a couple of weeks later the new PW prices rise from $3500 to $3900, and I received a repriced contract showing an increase of main panel upgrades north of $3000.)

Tesla Energy will likely add a 3' gutter box above your existing main panel (to span to the next stud) and divert circuits to a new (included in price) backup loads panel. The generation panel (included in price) will be home for the Powerwall and the solar breakers (microinverters). A gutter box has ample room to be creative. Your panel will have plenty of empty slots with blankout covers. Aesthetically, you could replace the dead front with a new one. It is probably easier to buy a new load center just for the dead front cover since your recently installed main panel is still manufactured.

 

[cr0ntab]

To make this question a bit more concrete, here is the approved single line diagram from the permits.

Approved_Electrical_Single_Line_Diagram2.pdf

From those plans I don't see where or how they're going to leave room for an EVSE or pool circuit in the main, particularly when it says "Note: there will be no other breakers in the main."

I think reducing the breaker size or adding a feeder tap like @wwhitney discussed are probably my only choices?

The plans don't make a whole lot of sense to me how they're laid out, but we'll see what happens.

I have all my desires to put the pool and EVSE circuits in front of the backup gateway in writing with a paper trail since the beginning.

​

 

[GenSao]

To make this question a bit more concrete, here is the approved single line diagram from the permits.

Approved_Electrical_Single_Line_Diagram2.pdf

From those plans I don't see where or how they're going to leave room for an EVSE or pool circuit in the main, particularly when it says "Note: there will be no other breakers in the main."

I think reducing the breaker size or adding a feeder tap like @wwhitney discussed are probably my only choices?

The plans don't make a whole lot of sense to me how they're laid out, but we'll see what happens.

I have all my desires to put the pool and EVSE circuits in front of the backup gateway in writing with a paper trail since the beginning.

​

Based the single line diagram, It looks like your EVSE and pool circuits may be relocated to behind the the backup gateway. Just curious, why would you want them in front of the backup gateway? I would think it would be nifty to maintain the ability to charge your car when the power is down.

 

[SoundDaTrumpet]

To make this question a bit more concrete, here is the approved single line diagram from the permits.
...
The plans don't make a whole lot of sense to me how they're laid out, but we'll see what happens.
...
I have all my desires to put the pool and EVSE circuits in front of the backup gateway in writing with a paper trail since the beginning.
​

Surprised your contractor didn't put any transmittal disclaimers prohibiting posting this online. Tesla Energy sure does. The planning document looks very close like my Tesla Energy ones.

Check what the NEC load calculation is for whatever is being backed up (estimate yours is 125A), and swap the 200A main breaker with say a 125A.

 

[wwhitney]

If the answer to one of the questions on the Home Depot website is to be believed, the main breaker in that meter main is not field replaceable. So complying with 705.12(D)(2)(3)(b) would not be an option.

You could still comply with 705.12(D)(2)(3)(c) by using a 125A breaker to your gateway, and then using a 100A breaker to your non-critical loads panel.

Cheers, Wayne

 

[Mickey Mouse]

Ok so you’re information of one powerwall will backup all of my 20 amp and below circuits are all going to be backup on a sub panel Tesla will install, correct?