Tesla surprises with a $4800 bill on existing $5300 install contract

[cali8484]

Its now been a month and my 3 Powerwalls and all 4 panels are just sitting there not yet wired. I struggled through the crazy billing and Tesla had a local contractor contact me to sort out their mess. They just could not figure out how to get the wiring to work out. I spoke to the local contractor who decided he needed to come over to understand how to best arrange the wiring to and from my main panel and the new equipment wall. We worked out a scheme that wasn't too bad but he decided a new main panel with meter and disconnect only made sense to both fit on the PG&E side for the meter and provide a splice area where breakers would have been. Then to use wiring troughs flying over top to wire main feed from disconnect and spliced service wires ( 200A house, 100A house, and 50A pool) to the top of my wall and then to the backup and non backup panels. So I extended my wall toward the existing service by 7 inches and dug a trench to reroute the solar directly to the generation panel. We will reroute wires that didn't need to go up my service pole such as the solar and pumps on the ground. That minimizes the splicing needed in the new panel empty space.

After he and I worked out this plan, he sent a cost to Tesla. Then Tesla removed the 2 items from my contract that were wrong, the solar meter and PW pad. That reduced the cost by about $1500 and Tesla charged me about the same for the new panel, permit changes and accepted the labor due to their bungling. That means my new contract is roughly the same. So now its been almost 2 weeks and Tesla says they are waiting for purchasing to send a contract to the local contractor. This project has been a real nightmare and its surprising Tesla can install any complex job due to their incompetence and horrible internal communication and coordination. I was happy with their manager who took over and arranged getting things right so far.

So it just sits looking like this waiting for completion.

View attachment 569514

What a nightmare. Do you think a third-party installer would have done much better?

 

[Vines]

I looked at Eaton's catalog of CH products, I didn't see any 4 position branch breakers or subfeed lugs.

Cheers, Wayne

I went to UL and CSA seeing if they would take our money to test and approve the 4 pole breaker HOM2200BB to land on the SC2040M200 panel, assuming we removed all the other breakers inside it.

Will see what they say, if its $5k one time plus $1.5k per service panel to relist it may be worth the testing time. It seems silly to pull out a perfectly good service if there is an alternate path.

What a nightmare. Do you think a third-party installer would have done much better?

Depends on the installer. I know some that would make similar mistakes, and others (I work for one) who would see this coming before the contract. Its pretty clear to anyone knowledgeable who is looking at the pictures of the panel.

 

[sorka]

Sorry if I seemed combative, its a subject that comes up a lot. I see this variously being dangerous to costly for the customer but is also the (bad) reason why a customer might choose a cheaper installer. The cheap installer just know the AJH doesn't know better, slap some subfeed lugs in there and go.

With us at the cutting edge of PV and ESS installations we have to self regulate and not give our industry a bad name. It only takes a couple fires, someone doing something stupid before the hand of regulation slaps us down.

If I decided to go with 2 powerwalls and not three, would a 100 amps as a feeder be sufficient? What is used to factor in the total load? The 8.16KW system where I'll have it installed has a theoretical AC output max of 6800 watts (June 23rd at noon). Powerwalls are 5KW each continuous but 7KW instantaneous for a few seconds. If we have to use the full instantaneous values, then I need 86 amps which is 6 amps over max for a 100 amp branch. If the rules only consider continuous loads, then 70 amps is enough. But I'm not an electrician and I don't know what goes into load calcs for a branch. Of course the NEC 220 calcs need to be done for the whole panel so it might be disqualified on that alone.

 

[wwhitney]

Take the maximum solar inverter output current per the spec sheet (doesn't matter how many panels you have)
Multiply that by 125%
Add 30A for each Powerwall

The result is the smallest size feeder you can use, considering the onsite generation. As you note, if the feeder also supplies loads, then you need to do a load calculation for the feeder as well.

So for a 100A feeder with (2) Powerwalls, you are limited to 32A solar inverter output current. The inverter would be typically labelled as 7.68 kW AC (or smaller).

Cheers, Wayne

 

[Vines]

You use the max continuous output rating of the PV inverters or Powerwall inverters x 1.25.

3 Powerwalls is actually an 80A breaker (78A actual) instead of a 90A. 20.8 A is the max output value for each Powerwall unit output

 

[sorka]

So with two powerwalls, that's 41.67 amps which would leave 38.33 amps left for an inverter or roughly 9200 watts?

 

[Vines]

This is the most simple way to put it yes.

There is no reason really why you cannot have 10 powerwalls on that 100A feeder as long as they collectively don't allow more than 100A through the breaker (83A continuous) This is better described in the 2020 code and in this article. (currently site down but should be up in a day or less)
https://iaeimagazine.org/magazine/f...normal-and-emergency-power-sources-for-homes/

Basically the Gateway 2 is a microgrid interconnect device (MID). As long as it only takes up to 100A (83A cont.) from, and only backfeeds 40A to the main service panel bus there is no reason why you cannot supply 200A worth of loads with enough powerwalls on the other side of the gateway, even despite the 100A branch circuit connection.

Once the AHJ approve the idea of the MID the door is open to do less service upgrades, even with giant systems. The real question is what the AHJ will trust. Currently its a software setting for charge and discharge rates. I sort of wish there were micro switches for charge and discharge rates inside the GW2 similar to how the HPWC setting changes for different breaker sizes.

 

[sorka]

If I have my Tesla charger on that same branch circuit. i.e. a sub panel in the garage with the solar and powerwalls, intuitively you'd think the charger wouldn't increase load and in fact could only decrease maximum load down the 100 amp line back to the main breaker....or is there something that prevents that?

 

[Vines]

Power will flow freely from the PV to the car charger and not from the grid in that case.

 

[sorka]

Power will flow freely from the PV to the car charger and not from the grid in that case.

Right I totally figured that so it would only serve to reduce load on that branch circuit. I was just wondering if there were any whacky NEC rules that prevent such a configuration?

 

[BrettS]

Right I totally figured that so it would only serve to reduce load on that branch circuit. I was just wondering if there were any whacky NEC rules that prevent such a configuration?

Remember that the powerwalls can also charge from the grid when stormwatch is active. In the worst case scenario you could have the car charging as well as the powerwalls charging before a storm and overload that 100A circuit.

 

[sorka]

Remember that the powerwalls can also charge from the grid when stormwatch is active. In the worst case scenario you could have the car charging as well as the powerwalls charging before a storm and overload that 100A circuit.

Good point. What is the maximum PW2 charge rate? I don't see a firm spec. See several claim it's limited to 3.3KW to PW. Is this configurable?

 

[BrettS]

Good point. What is the maximum PW2 charge rate? I don't see a firm spec. See several claim it's limited to 3.3KW to PW. Is this configurable?

I believe it is actually 5kW per powerwall. It is not configurable. At least not by the end user. It’s conceivable that Tesla might be able to change it, but I’ve never heard of them doing so.

 

[sorka]

I believe it is actually 5kW per powerwall. It is not configurable. At least not by the end user. It’s conceivable that Tesla might be able to change it, but I’ve never heard of them doing so.

So I'd basically need to set Tesla charger to to max 32A which I'm fine with.

 

[Vines]

The GW2 can limit the total draw through itself. So for instance if the EV charger was drawing 48A and stormwatch mode came on, the other 5 of the Powerwalls on a theoretical 100A circuit would only charge to the rate that keeps the 100A breaker safe. This is only configurable by your installer.

The GW2 reads in real time the draw through itself, so in the same theoretical instance, you started drawing 125A from your 100A feed, the GW2 will tell the powerwalls to discharge to prevent your popping that breaker from overload as well.

 

[wwhitney]

20.8 A is the max output value for each Powerwall unit output

So the data sheet says "Real power, max continuous 5 kW". And 5 kW is 20.8A @ 240V, or 26A after the 125% factor.

But the data sheet also says "Apparent power, max continuous 5.8 kVA." And 5.8 kVA is 24.2A @ 240V, or 30.2A after the 125% factor.

I would think for NEC purposes you'd need to use the latter numbers, because if the load power factor is not 1, the Powerwall can put out 24A continuously.

Cheers, Wayne

 

[Vines]

You

So the data sheet says "Real power, max continuous 5 kW". And 5 kW is 20.8A @ 240V, or 26A after the 125% factor.

But the data sheet also says "Apparent power, max continuous 5.8 kVA." And 5.8 kVA is 24.2A @ 240V, or 30.2A after the 125% factor.

I would think for NEC purposes you'd need to use the latter numbers, because if the load power factor is not 1, the Powerwall can put out 24A continuously.

Cheers, Wayne

You always have the best responses, Cheers.

 

[pgrovetom1]

What a nightmare. Do you think a third-party installer would have done much better?

I know a third party installer would do better. Tesla sent one team with one of their electricians and he had a mental plan that included my existing main panel and they put in the PWs and panels in my photo, then a second team came to "finish" it without knowing what "it" is. They second electrician had a completely different plan that included a new main panel but his mental plan described for all the rewiring was incomplete. They both left baffled. Then Tesla sent a third party electrician and he and I worked out what we thought would be the cleanest way. I spoke with all 3 electricians about their plan and thinking and only the 3rd party guy really thought it through. The first Tesla electrician put up the PWs, a 400A non-backup panel, a 200A backup panel, and the gateway as in my photo. The plan myself and the third party electrician came up with understood where the various wires would be arriving on the wall ( over top, along the ground, right, left, top, bottom) and the installed locations of the various panels are not in the best places. So they might get moved ( argh!!).

The plan we decided on is a little contingent on finding the right new main panel but I suspect there are good ones. It will be similar to my current panel with the existing PG&E coming up from below via conduit directly into the bottom of the meter left side of the panel. The right side of the panel will only use its main 200A breaker as a main disconnect. The meter connects left to right to this 200A main breaker. The house side of the main breaker goes out the top of the panel into a wiring trough/box ( similar to the small one in the photo) and flies over top to the top right of the equipment wall. Then that is wired to the non-backup panel which is wired to the gateway.

Then we will move the 2 solar systems and wire them underground in conduit to the lower left of the equipment wall. Then from there they will go to moved disconnect switches and then to the generation panel. That gets the solar and disconnect switches out of the main panel reducing the wiring carried over top. My existing 50A pool feed, the 200A house feed and 100A house feed that are already in my existing panel will be put back into the new panel mostly empty ( only a 200 disconnect) left side where they will be spliced and routed out the new main panel top into another wiring tray running alongside the main 200A feed from PG&E. Once on the wall they will be routed to the backup panel ( 50A pool) and the other 2 ( 200A and 100A) will be routed to the new backup panel. Then the 3 pump wires sets will be rewired longer or spliced and run into the same trough and go to the respective backup or non-backup panel.

I only told much of our plan because what is written above was not really thought out by either Tesla electrician which is why Tesla threw up their hands and brought in the 3rd party electrician where he and I walked through each wire flow from where it is through to where it must go and how will we do that. I suspect Tesla has people who could do this but the 2 that came over did not have the time and tried to wing it roughly and then just left. My impression was that neither planned to return so didn't seem bought in such that they would do it right since they would have to deal with it next time.

I got a message from the 3rd party electricians and they tentatively plan on doing the job on August 19th and 20th.. I'm keeping my fingers crossed.

 

[BrettS]

I believe it is actually 5kW per powerwall. It is not configurable. At least not by the end user. It’s conceivable that Tesla might be able to change it, but I’ve never heard of them doing so.

So I just wanted to follow up on this because apparently I was mistaken. I believe that the max charge rate per Powerwall is 5kW, but it would appear that the system doesn’t charge them that quickly in stormwatch mode. I want into stormwatch mode because of tropical storm Isaias and I’ve been watching my powerwalls charge today. My 4 Powerwalls are charging at a rate of 13.3kW total, or 3.325kW per Powerwall. It’s sending all of my solar power to the powerwalls and then using as much as it needs to from the grid to get to 13.3kW. As the solar production goes up and down as clouds pass overhead it will take less or more from the grid to keep a constant 13.3kW going to the powerwalls.

 

[miimura]

From what I've heard, it will only grid charge up to about 3.3kW per PW. If you had more solar, it would charge at rates between 3.3kW and 5kW. It just won't use the grid to exceed 3.3kW.