Main Panel Upgrade 17.2kW Solar + 2 powerwallplus + 1 powerwall2?

[TTSSBB]

Tesla provided attached

 

[TTSSBB]

Tesla provided attached design for my 17.2kW solar + 3 powerwalls (2PW+, 1PW2.0).

During install, they said that they couldn't fit a 175A breaker into my panel and tried to get me to accept a 125A breaker. The load calc was about 157A. I don't know why they didn't catch this during site inspection.

Am I suppose to get a panel upgrade? If so, am I suppose to get a 225A buss bar with a 200A panel or is my issue finding a 175A breaker that fits into my existing main panel.

How does the system work for the design below? I can receive up to 130A from the 3 Powerwalls + 45 from the grid before tripping the 175A breaker? How does the 17.2kW solar panel fit into the equation for the current? How does the 120% rule calculate out for below?

Much thanks to the community for any help and guidance!

 

[arnolddeleon]

The ideal "cheap" option is a 175A breaker from your main panel to the gateway but I'm guessing your panel doesn't have a listed option that supports that. The other option is a main panel with 200A breaker and just 200A pass through (which is what I have).

However, unless you have sustained loads that add up beyond 125A I would take the 125A option (unless Tesla is paying for a panel upgrade). Your load center is still a 200A/225A load center. Your solar and Powerwalls can supplement the grid supplied 125A so if you happen to spike above 125A you will be fine. You have 125A (grid) + 130A (Powerwalls). This assumes they don't have to downsize the breaker to load center. I'm surprised that isn't a 200A breaker to the new load center.

Not an authority, just an avid reader of good posts from the likes of @Vines and others.

 

[TTSSBB]

Thanks for the suggestions and comments!

What do you mean by just 200A passthrough? Can you provide a simple schematic? Tesla isn't providing any answers to my questions and it's really hard to communicate with them.

For the 125A suggestion:

1) does section 6 and 8 both have to have same breaker size? The load center is the section 6 / (E) ? and can be left at 175A or 200A?

2) I assume the 125A is for section 8 in (A) of the schematic?

3) Any 120% rule implications?

Thanks again!

 

[hiltxan]

I had the exact same issue - kept asking Tesla for a 200A connection but they wouldn't do it and kept it at 125A. I asked for a load calculation and they said they didn't do one. I was arguing with Tesla back and forth and they wouldn't budge so I gave up to try to lock in NEM 2.0 (this was before they sent the interconnection application first). In reality, I think 125A is enough, even though I have an induction stove, electric oven, EV charger and adding 2 heat pumps in the future. Just be careful with the EV charging and maybe set a lower amperage and charge only at night. I did my own load calculation according to NEC and it said I needed a 325A panel which I think is overkill .

My schematic is similar to yours. I couldn't find a bigger breaker myself online for the Murray main panel, which may be the reason why it can't go any bigger. But the electrician during the install and the Tesla inspection coordinator both said I could probably upsize it to 150A later on since they used a 1 gauge wire. I got their phone numbers when they were here and will call them back if I do end up needing 150A. The distribution panel is limited by the connecting breaker on the main panel - it doesn't seem like the powerwalls can supply extra amperage on top of the connecting main panel breaker.

The 120% rule is actually 1 of 3 options for how your gateway connects to the main panel. See thread 120 percent busbar NEC rule

 

[TTSSBB]

Thanks hiltxan! Can you send me the link for the 150A breaker? Since I have 3PWs with 130A, it maybe better in my case? My load calc (performed by Tesla) was almost 160A. I don't know the model of my main panel, but is older type...maybe we have the same kind. The label is worn and hard to read.

 

[hiltxan]

Every panel uses different breakers so what may work for mine may not work for yours. The electrician basically said it was doable but didn't mention which one he was going to use. The ones I looked up from old spec sheets only listed 125A circuit breakers that were compatible, but maybe they know something I don't. For example, if they use a breaker suited for a main breaker and then use that one for the gateway connection, essentially having two main breakers on one panel.

 

[arnolddeleon]

Thanks for the suggestions and comments!

What do you mean by just 200A passthrough? Can you provide a simple schematic? Tesla isn't providing any answers to my questions and it's really hard to communicate with them.

For the 125A suggestion:

1) does section 6 and 8 both have to have same breaker size? The load center is the section 6 / (E) ? and can be left at 175A or 200A?

2) I assume the 125A is for section 8 in (A) of the schematic?

3) Any 120% rule implications?

Thanks again!

5 years ago Tesla replaced my combination meter/load center with a new panel that had a meter base and main breaker without any slots for load breakers. It just had lugs to pass through to a load center (or the gateway). In your diagram the first 175A breaker would disappear.

The incremental labor to replace your main panel shouldn't be that much because the loads are already being relocated. However, coordinating it with utility is probably the thing that adds schedule complexity and even more costs.

I don't know if 6 and 8 have to be the same. The decision would be easy if they didn't. But given that they had 175A instead of 200A seems to suggest they are matching them. My assumption had been that with PCS enabled they can feed your load center the max that it can handle (200A) without overloading the main panel because with PCS they are controlling the output of the inverters to make sure the main panel feed doesn't exceed its rating.

 

[morph3ous]

What they did for our system is removed all loads from our 200 amp panel with meter base. All they left in that panel was the disconnect and a 200 amp breaker at the bottom that goes to the gateway. Then they put in a new panel fed exclusively by the gateway and moved our existing loads to it.

I’m not sure this information helps in your case. Posting it in case it does.

16.3KW of solar w/ Tesla inverters and 4 PowerWalls.

 

[Vines]

Likely the correct solution here is to replace the main panel but you can probably make it work ok as a partial home backup system.

As you have, many main panels especially the more compact and center-fed versions cannot take large branch circuit breakers, so it sounds like 125A is the largest breaker you can supply.

As it is designed now, your Powerwalls could supply some additional power above the 125A available from the grid while they are charged.

It might be worthwhile looking at the loads you are backing up, or taking a second look at your load calculations. Your calculated load isn't that far off the ability for a 125A breaker to supply it.

Likely the system installer will consider setting the PCS controls such that you don't overload the busbar or the 125A breaker.

 

[h2ofun]

Likely the correct solution here is to replace the main panel but you can probably make it work ok as a partial home backup system.

As you have, many main panels especially the more compact and center-fed versions cannot take large branch circuit breakers, so it sounds like 125A is the largest breaker you can supply.

As it is designed now, your Powerwalls could supply some additional power above the 125A available from the grid while they are charged.

It might be worthwhile looking at the loads you are backing up, or taking a second look at your load calculations. Your calculated load isn't that far off the ability for a 125A breaker to supply it.

Likely the system installer will consider setting the PCS controls such that you don't overload the busbar or the 125A breaker.

For what all this stuff costs, do it right, replace the main panel. I did mine.

And if I could just have put everything in one panel.

 

[CrazyRabbit]

Likely the correct solution here is to replace the main panel but you can probably make it work ok as a partial home backup system.

As you have, many main panels especially the more compact and center-fed versions cannot take large branch circuit breakers, so it sounds like 125A is the largest breaker you can supply.

As it is designed now, your Powerwalls could supply some additional power above the 125A available from the grid while they are charged.

It might be worthwhile looking at the loads you are backing up, or taking a second look at your load calculations. Your calculated load isn't that far off the ability for a 125A breaker to supply it.

Likely the system installer will consider setting the PCS controls such that you don't overload the busbar or the 125A breaker.

He would have to upsize the main breaker in his New backed up loads panel.

 

[TTSSBB]

What they did for our system is removed all loads from our 200 amp panel with meter base. All they left in that panel was the disconnect and a 200 amp breaker at the bottom that goes to the gateway. Then they put in a new panel fed exclusively by the gateway and moved our existing loads to it.

I’m not sure this information helps in your case. Posting it in case it does.

16.3KW of solar w/ Tesla inverters and 4 PowerWalls.

Hi, in your case, what breaker size did they use in your distribution panel? In the schematic they gave me, they put a 175A breaker in both the main panel (which is the one which "doesn't" physically fit") and one 175A breaker in the distribution panel where all the loads are relocated. I wonder why they need that 175A breaker in the main panel. Can't they just use the existing 200A breaker in there. Then my setup sounds like yours. Anyway you have a schematic you can post? It's a blackhole with Tesla...no feedback for week now from them.

 

[TTSSBB]

For what all this stuff costs, do it right, replace the main panel. I did mine.

And if I could just have put everything in one panel.

My challenge is that I asked Tesla what specs etc. I need if I need a main panel upgrade and I get zero response from them. They claim they are working on it...for about a week now. I don't know specifically what to ask the electrician to do and need some confirmation as to what the electrician suggests would even meet Tesla spec. Other electricians want Tesla feedback to confirm before performing a job.

 

[TTSSBB]

Tesla claims my NEMA2.0 is submitted and I do not have to worry even if my install goes past the cutoff date so long as my PV layout doesn't change. Breaker changes or panel changes does not affect the application per Tesla. Hope this is true as I have asked numerous times.