Tesla string shenanigans or sorcery?

[bcroe]

You currently have 1 qty #6 bare copper wire and 6 qty #10 PV wire in a 1" EMT conduit.

I did not know, that it was OK to run bare copper wire in EMT conduit. Bruce Roe

[oregon_phil]

Thank you, Phil, I appreciate the explanation and you running the numbers. Surprisingly, I'm following most of it I think. It seems that was the trade-off. As I've mentioned in another thread, Tesla definitely makes trade-offs and this sounds like one of them. Armed with this, I may engage with Tesla but keep my expectations low. I would imagine they would want to see a full year of production before making any changes. With my initial analysis I estimated a 613 kWh loss with the NW panels "pulling down" the SW panels, but that's not currently happening. I'll just have to keep analyzing it going into Fall/Winter to see if that holds up.

As for the roof pictures I'm trying to decide what to do with that. With the stories I hear about Tesla breaking tiles, I do want to get some pictures of the tiles after the install and I do want to get pictures of the junction boxes. I do also want to address the pigeon problem I have. And finally I want to plan on cleaning the panels.

The question is, do I get a ladder and the equipment and do that myself? I do a lot DIY for my car and house, but my wife is nervous about the heights involved.

Thanks again for your help.

Now that you know the tradeoff, you can make an educated decision on what to do with the wiring. At least you know what's going. In the end, it probably doesn't matter. More people hours on the roof might mean more chance of broken tiles. A roof leak is way worse than lower PV production.

As for cleaning, I used to go up on my pole barn with a full safety harness to clean my panels, but in Oregon it rains enough in the winter to clean my panels. Even with a safety harness, one fall or trip on my roof cleaning my panels could cause an injury. and I'm not getting any younger. Any PV improvements from cleaning were pretty much gone in a week. I live in farm country. Now I just let nature clean my panels.

[azdave]

...And finally I want to plan on cleaning the panels.

The question is, do I get a ladder and the equipment and do that myself?

Most of us don't bother except in special circumstances. The risk of damage to the roof, gutters or yourself is not worth the small amount of savings. Paying someone to clean them will never pay off in increased efficiency either. Slips and falls from the roof cost exponentially more than what you'll gain from regular panel cleaning.

https://www.solarpaneltalk.com/forum...aning-services

[OCJ]

I thought NEM 3.0 was eminent in June 2021 and I chose to self install so I could do main panel changeout, new subpanels and solar install simultaneously. It was costing me $10 per day for electricity so timing was important for a couple of reasons.

That's the deadline I was initially shooting for too. When it got delayed the urgency level for me went down a bit. If I had to do it again I would ping them weekly to keep the ball rolling. It all worked out in the end though.

[OCJ]

Tesla has already proven they can run 4 qty #10 PV wires with #6 bare ground wire in a 3/4" EMT conduit (see group bundle #3).

The problem is the PV wire and the 1" conduit. I suspect there is a junction box where all the 3/4" EMT conduit comes together then transitions down into a 1" EMT conduit into your inverter. Picture please.

You currently have 1 qty #6 bare copper wire and 6 qty #10 PV wire in a 1" EMT conduit. This is perfectly fine. Fill percentage number is green. See picture 6 PV.jpg.

Since you need to add two more wires, Tesla would need to add two more #10 PV wires. 1 qty #6 bare copper wire and 8 qty #10 PV wire in a 1" EMT conduit violates fill percentage per Southwire fill percent calculator. Fill percentage number is red. See picture 8 PV.jpg

One way to fix the 1" conduit fill percentage problem is to switch from #10 PV wire to #10 THHN wire. Doing this makes the fill percentage acceptable in a 1" EMT conduit. See picture THHN.jpg

The deal is that they have to make the PV wire to THHN transition somewhere. My system has a large junction box on my roof right under my array where all PV wire is transitioned to THHN.

I have to assume there is a junction box at splice.jpg. If the installer used a junction box that is large enough where the splice is made (splice.jpg), then they can make the THHN transition there. Pulling new wire with old wire in EMT is not a good idea I am told. So in this case, I would pull out the old wire from the junction box to the inverter and pull a pull rope too. Then install new THHN #10 wire (4 qty) and one ground wire at the same time.

I'm not an installer nor an EE, so please check my work. It all depends on where the junction box is located.

Thank you, Phil, I appreciate the explanation and you running the numbers. Surprisingly, I'm following most of it I think. It seems that was the trade-off. As I've mentioned in another thread, Tesla definitely makes trade-offs and this sounds like one of them. Armed with this, I may engage with Tesla but keep my expectations low. I would imagine they would want to see a full year of production before making any changes. With my initial analysis I estimated a 613 kWh loss with the NW panels "pulling down" the SW panels, but that's not currently happening. I'll just have to keep analyzing it going into Fall/Winter to see if that holds up.

As for the roof pictures I'm trying to decide what to do with that. With the stories I hear about Tesla breaking tiles, I do want to get some pictures of the tiles after the install and I do want to get pictures of the junction boxes. I do also want to address the pigeon problem I have. And finally I want to plan on cleaning the panels.

The question is, do I get a ladder and the equipment and do that myself? I do a lot DIY for my car and house, but my wife is nervous about the heights involved.

Thanks again for your help.

[Ampster]

They asked me to fix them and send proof before they would schedule the install. So in my case no, they didn't do the tiles, they asked me to fix them.

I thought NEM 3.0 was eminent in June 2021 and I chose to self install so I could do main panel changeout, new subpanels and solar install simultaneously. It was costing me $10 per day for electricity so timing was important for a couple of reasons.

[oregon_phil]

I didn't observe that the "splice" on the roof is a PV Y adapter per your schematic.

They obviously made some MC4 connections onto PV wire in the field (non factory terminations), so the question becomes how did they make the transition from wire into the end of EMT?

Maybe they put the PV Y adapter in a junction box? More questions....

[oregon_phil]

Yes, that's what I'm wondering about, un-paralleling the strings. I initially was going to call them and ask them to un-parallel them, but I wanted to quantify the data first. That's when I ran across that NW string producing more than PVWatts estimate, and the SW string producing less, but the average being the same. Although as J.P.M. pointed out this could be all within the margin of error of the tools.

For 1 and 2, here are the appropriate screenshots, all run through conduit on the roof:




I set up Powerwall-Dashboard so here's the output from pyPowerwall:


As for 3, I'm wondering that myself. The other panels were grouped in 5 and 7... if they had been 6 and 6, would they have put them in parallel also?

Either they did it to save running another pair, they do it by default, there wasn't enough room, or their AI knows something we don't. I don't know.

Tesla has already proven they can run 4 qty #10 PV wires with #6 bare ground wire in a 3/4" EMT conduit (see group bundle #3).

The problem is the PV wire and the 1" conduit. I suspect there is a junction box where all the 3/4" EMT conduit comes together then transitions down into a 1" EMT conduit into your inverter. Picture please.

You currently have 1 qty #6 bare copper wire and 6 qty #10 PV wire in a 1" EMT conduit. This is perfectly fine. Fill percentage number is green. See picture 6 PV.jpg.

Since you need to add two more wires, Tesla would need to add two more #10 PV wires. 1 qty #6 bare copper wire and 8 qty #10 PV wire in a 1" EMT conduit violates fill percentage per Southwire fill percent calculator. Fill percentage number is red. See picture 8 PV.jpg

One way to fix the 1" conduit fill percentage problem is to switch from #10 PV wire to #10 THHN wire. Doing this makes the fill percentage acceptable in a 1" EMT conduit. See picture THHN.jpg

The deal is that they have to make the PV wire to THHN transition somewhere. My system has a large junction box on my roof right under my array where all PV wire is transitioned to THHN.

I have to assume there is a junction box at splice.jpg. If the installer used a junction box that is large enough where the splice is made (splice.jpg), then they can make the THHN transition there. Pulling new wire with old wire in EMT is not a good idea I am told. So in this case, I would pull out the old wire from the junction box to the inverter and pull a pull rope too. Then install new THHN #10 wire (4 qty) and one ground wire at the same time.

I'm not an installer nor an EE, so please check my work. It all depends on where the junction box is located.

[OCJ]

Also, those few days I actually dropped my Powerwall reserve down to 5% just to see if I could not pull anything from the grid. I'm not going to do that long term, but it is cool being "invisible" from the utility in terms usage. Also, it was a dang near perfect solar day so this isn't always reproducible and of course won't be going into Winter.

Utility view:



House view:

[OCJ]

Thank you for the reply.
Yes, that is a credit against future billing, not what you'll get a check for.
Any guess as to how long it'll take to break even on the power wall using differential T.O.U. rates ?

Yes, I expect I'll use some of that credit up in Winter. I know the excess generation gets < $.04 per kWh during True-Up.

I'm still working out the ROI for the Powerwall. I know it's long, but I'm not sure how long. As I mentioned, I did get it knowing that the ROI was longer, but wanted the ability to tweak how I run the system. Also, I may be able to get all or some of the Powerwall cost offset, in that case the ROI question is moot for me.

When I initially got PTO, I switched from Self-Powered to Time-Based Control, which runs 100% off the Powerwall between 4pm and 9pm and sends solar to the grid during peak. I was pushing around 9 kWh peak to the grid. I was also sending around 25 kWh Off-Peak during the day, until I got an EV.

At the beginning of August, I switched to Self-Powered with 20% reserve. So during On-Peak I only send what my house doesn't use. I also started charging the EV inside my solar production, from 11am to 3pm. So for Aug 17, I generated 55.7 kWh, pulled 0.3 kWh from the grid, pushed 19.1 kWh to the grid, and charged my EV at 4.3 kW for a couple of hours to get it back up to 80%. By doing this I minimize my NBCs.

Next up I'm thinking about creating my own Time-Based Control schedule to run off battery from 4pm to midnight, and maybe switch to EV-TOU2.

I know I'm only talking about $130 in NBCs for the year, but at this point of recently having a baby, switching jobs, and getting a new house, since my other hobbies have been destroyed this is my new hobby for now.

[OCJ]

Thank you for the picture of your layout. If you don't mind a slightly different set of questions:

1) Where is the electrical parallel connection for the SW and NW panels made? In the picture SW NW Panels.jpg is the parallel connection made on the roof at point A, or at the inverter at point B? Or some other place?

2) What type of wire did they use between arrays and how is the wiring run between arrays? On the roof in conduit? Down through the roof, in the attic?

3) There is very little online documentation for the Tesla 7.6kW 4MPPT inverter. I was able to find one picture of the internal wiring. I am guessing that the DC inputs have a jumper between 1+/2+ and 1-/2- or 3+/4+ and 3-/4-. Have you ever looked inside of the inverter after it has been shutdown?

You are concerned about paralleling SW and NW strings. Depending on where they made the parallel connection, what wire they used between between arrays (PV or THHN) and how they ran the wire between arrays (in the attic, in conduit, type of conduit, etc, ), it might be easy to un-parallel your solar arrays. Your inverter has 4 MPPT inputs. I'm at a loss on why your installer would choose to parallel inputs other than to save money on wire, labor, maybe doesn't have room in conduit?

Yes, that's what I'm wondering about, un-paralleling the strings. I initially was going to call them and ask them to un-parallel them, but I wanted to quantify the data first. That's when I ran across that NW string producing more than PVWatts estimate, and the SW string producing less, but the average being the same. Although as J.P.M. pointed out this could be all within the margin of error of the tools.

For 1 and 2, here are the appropriate screenshots, all run through conduit on the roof:




I set up Powerwall-Dashboard so here's the output from pyPowerwall:


As for 3, I'm wondering that myself. The other panels were grouped in 5 and 7... if they had been 6 and 6, would they have put them in parallel also?

Either they did it to save running another pair, they do it by default, there wasn't enough room, or their AI knows something we don't. I don't know.

[OCJ]

Roof tiles? I have heard other stories about Tesla refusing to do roof tiles? I had a similar quote from Tesla in June 2021 but I knew I wanted to upgrade my service panel and was concerned that would delay the install. Interestingly their proposal included some panels facing ENE My proposal was with no Powerwall and they had recently changed their policy and I also thought my install would get delayed in favor of more profitable ones with Powerwalls. I did a self install with the help of some professionals and the cost, including the service panel upgrade was about the same as their proposal.

They asked me to fix them and send proof before they would schedule the install. So in my case no, they didn't do the tiles, they asked me to fix them.

[J.P.M.]

Before tax credit and before sales tax, $24k for 9.6 kW and $10.5k for the Powerwall+. I checked a couple of local installers as well as https://www.californiadgstats.ca.gov/find_installer/ and decided the price was too good to pass up. Order placed 1/11/22, installed 5/11/22, PTO 6/23/22. The biggest ball drop was 6 weeks between the site visit and them telling me I needed to replace some roof tiles.

All in all the experience was fine for me, even though I hear others have major issues. I managed to generate $703 in credits through the beginning of August before getting an EV so now it's just my "hobby" to tweak whatever settings I can.

Thank you for the reply.
Yes, that is a credit against future billing, not what you'll get a check for.
Any guess as to how long it'll take to break even on the power wall using differential T.O.U. rates ?

[oregon_phil]

Thanks for your comments J.P.M. At the time I ordered solar we had only been living in this house a month. Since I was on SDG&E at the previous house, though, I pulled up the previous 1 year of data and made some guesstimations. The old house was 2,100 sqft, the new one was 2,800 sqft, a +33.33% difference, but the new house was also "newer" so I settled on +20%. The previous one year usage at the old house was 7,800 kWh with August being the worst at 1,259 kWh. So my guesstimate for the new home was around 9,400 kWh per year.

We also planned on an EV and a pool. Our mileage was pretty much exactly 30 miles per day on average, so around 10,950 miles/yr. I went with a 2.4 mi/kWh so that gave me an annual usage of 4,560 kWh. So now at around 13,960 kWh per year. And for the pool I believe I estimated around 1,500 kWh per year. That gives me 15,460 kWh per year expected.

Now, we have an EV. And our house turned out to be even more efficient than I thought, my annual house projection actually went down to 7,400 kWh.

Current: 11,960 kWh (higher efficiency and EV, 7,400 kWh house usage + 4,560 kWh EV usage)
Expected: 13,460 kWh (with pool, +1,500 kWh)

So for now I'm overproducing quite a bit, which is also why I'm looking at some electric space heating for winter for our bedroom and nursery.

As far as the roof goes, I don't think there is room for more panels SW and SE. I've linked to the diagram and pic. I think Tesla did a decent design given the limitations of my roof.



Regarding the NW and NE panels. I calculated them with a marginal cost of $2.70 per watt ($2.50 plus tax) since the SE and SW panels were going to be purchased no matter what. So the worst producing one, the NE panels, is $5,400, which is $2.70 * 5 panels * 400 watts with an annual production of 2,599 kWhs. Assuming every kWh is used, that's $1,170 per year from those panels (at $.45 per kWh). I estimate a 6-year ROI on that lowest productions set of panels.

I'm going to dig into the NW and SW data a bit more, maybe spot check a day in June and July. See if they exhibit that same variance.

I was looking forward to that SW set of panels bringing me good returns late in the evening, as you pointed out, especially going into fall/winter. I was disappointed they put it in parallel with the NW panels, but I really am curious how that NW set of panels is going to hold up towards the end of the year. I'm thinking since I'm overproducing anyway maybe see how it goes out of curiousity. Also, no shading at all. I did also get storage to give me options, even though the ROI is further out, but that's another post.

Thank you for the picture of your layout. If you don't mind a slightly different set of questions:

1) Where is the electrical parallel connection for the SW and NW panels made? In the picture SW NW Panels.jpg is the parallel connection made on the roof at point A, or at the inverter at point B? Or some other place?

2) What type of wire did they use between arrays and how is the wiring run between arrays? On the roof in conduit? Down through the roof, in the attic?

3) There is very little online documentation for the Tesla 7.6kW 4MPPT inverter. I was able to find one picture of the internal wiring. I am guessing that the DC inputs have a jumper between 1+/2+ and 1-/2- or 3+/4+ and 3-/4-. Have you ever looked inside of the inverter after it has been shutdown?

You are concerned about paralleling SW and NW strings. Depending on where they made the parallel connection, what wire they used between between arrays (PV or THHN) and how they ran the wire between arrays (in the attic, in conduit, type of conduit, etc, ), it might be easy to un-parallel your solar arrays. Your inverter has 4 MPPT inputs. I'm at a loss on why your installer would choose to parallel inputs other than to save money on wire, labor, maybe doesn't have room in conduit?

[Ampster]

Roof tiles? I have heard other stories about Tesla refusing to do roof tiles? I had a similar quote from Tesla in June 2021 but I knew I wanted to upgrade my service panel and was concerned that would delay the install. Interestingly their proposal included some panels facing ENE My proposal was with no Powerwall and they had recently changed their policy and I also thought my install would get delayed in favor of more profitable ones with Powerwalls. I did a self install with the help of some professionals and the cost, including the service panel upgrade was about the same as their proposal.