Hello from Ventura, CA (and question about 400A service and parallel Sol-Ark configuration)

[ventura-diy]

Hello fellow community members!

I'm very glad to have found this forum, since I've been trying to complete a solar project for some months now, but have encountered many issues. I'm hoping to tap the collective expertise and generosity of the members on this forum to navigate my way to a fully operational system.

Attached is a naive single line diagram that I've determined might work for me. Could someone knowledgeable please take a look and comment (specifically about basic code compliance, and hardware choices, or if simplifications are possible/desirable). Will it work as I've drawn it? Thanks a bunch in advance.

For context, here's my situation, in brief:

• I live in northern part of greater Los Angeles (my house is in zip code 93021), so I'm subject to the full force of many rules and regulations from my HOA, my local AHJ, and of course SCE - but that is a secondary concern right now. The technical issues are what I'm trying to nail down first. My goal is to be "grid-independent" as much as possible with SCE as backup.
• I have 400A service from SCE, fed via underground lines to a outdoor wall mounted 400A meter-main panel (General Electric TM2440RMS) with around 37 breakers used on the main panel and a subpanel (lug only) inside the garage with another 20 breakers used.
• I want to back-up everything (all circuits should have access to the battery backup power). So perhaps ~19 kW of panels on the roof and ~60 kWh of batteries. Solar charging and battery discharging must be shareable.
• After much back and forth with a number of solar companies (and all kinds of misinformation), I've decided on a dual Sol-Ark 15K-2P system with the Renon Xtreme LV battery stacks.
  • 8 out of 10 solar companies in my region (as far away as west LA) backed out or gave me ridiculous quotes when I specified this is what I'd like to do - but that's another story for a different post
• Needless to say, I'm trying to complete the project affordably, so while 400A rated switches, panels, etc. would be nice, I'm mostly likely going to have live with 200A components as much as possible (is this true?), hence the line diagram details that I've drawn.

I've noticed there are threads in this forum that explicitly discuss parallel Sol-Ark configurations and hardware bits and pieces needed to get the system operational. Sorry I haven't read all those posts yet, and I can post this query on some thread there, if that would be better. Thanks

 

[DIYrich]

Usually people parallel SA to go from 50a to 100a for one 200a main panel.
In your case, I would make two separate 200a systems (one for each panel).
You can have a common battery bank.

 

[BentleyJ]

Agree with DIYrich. If each inverter is set up independently then each Breaker in the existing main panel simply feeds one Sol-Ark and each inverter feeds directly into its own subpanel. This would eliminate the distribution box.

Unless there is some reason the loads cannot be reasonably balanced between the 2 subpanels there is no particular advantage to operating the inverters as Primary-Secondary vs. 2 stand alone units. They could still share the same battery.

 

[ventura-diy]

Usually people parallel SA to go from 50a to 100a for one 200a main panel.
In your case, I would make two separate 200a systems (one for each panel).
You can have a common battery bank.

Agree with DIYrich. If each inverter is set up independently then each Breaker in the existing main panel simply feeds one Sol-Ark and each inverter feeds directly into its own subpanel. This would eliminate the distribution box.

Unless there is some reason the loads cannot be reasonably balanced between the 2 subpanels there is no particular advantage to operating the inverters as Primary-Secondary vs. 2 stand alone units. They could still share the same battery.

Thanks for your replies. Yes, I did think about that as well - i.e. have two independent Sol-Ark's, not paralleled, feeding each panel. Charging/discharging from the batteries remain the same. It saves some $ eliminating the distribution box (guesstimating ~$500). A few questions then:

1) is paralleling the Sol-Ark's, while do-able, not advisable? Have folks done this and encountered glitches, headaches, etc. that just doesn't make it worth it and it's better to balance the loads among the two panels and just let the units work independently?
2) the parallel configuration (for ~$500 more) enables me to route a up to 30 kW (instead of 15 kW) in case one panel does need more than 15 kW for some amount of time (e.g. I do plan to hook up a Level 2 charger to one of the panels in the future). Once again, is this flexibility not worth it in actual practice?
3) how does the software work then? Will I need current transformers for each of the Sol-Arks and will they coordinate somehow if I'm feeding back to the grid?

 

[BentleyJ]

Sol-Ark is a good inverter with generally above average firmware. Most users on the Forum seem to be satisfied. That said, operating inverters in parallel tends to be more difficult in the beginning getting them set up and balanced. Likewise if there are any issues that come up months or years later, parallel operation can make troubleshooting more difficult. Not trying to discourage you from parallel operation. In the end, the equipment needs to be set up to serve your electrical needs in the best way possible.

I would recommend making a spreadsheet for each subpanel and listing the proposed circuits in each. If you find that your peak usage would favor operating them in parallel then do that.

 

[DIYrich]

Not a problem with paralleling when used for 200a. The problem is with paralleling with 400a. Each SA is designed to passthrough 200a. If one goes down while passing 200+amps, that is a problem.

 

[ventura-diy]

A follow-up question: is my connection to the 400A panel correct (in the line diagram that I uploaded earlier)? I'm reading on various forums that what I have in the diagram is a "supply-side" tap that is subject to various NEC rules. So do I need to modify my diagram, to have the hot wires from the meter go to the polaris taps *before* the 200A breakers. Attached is a picture of a panel similar to mine. Note the "guard" at the top where the meter hot lines directly feed the two 200A breakers. What would a "line-side" tap mean in this case? Does it mean the meter hot wires are pulled out through the top separately in to the polaris tap and then via the disconnect to the inverters? In that case, could I not feed the output of one of the inverters back into the 200A breaker and bus bar of my main meter-main panel (and not have a separate subpanel) as I originally thought I would need. Somewhat confused.

 

[BentleyJ]

A follow-up question: is my connection to the 400A panel correct (in the line diagram that I uploaded earlier)? I'm reading on various forums that what I have in the diagram is a "supply-side" tap that is subject to various NEC rules. So do I need to modify my diagram, to have the hot wires from the meter go to the polaris taps *before* the 200A breakers.

Yes, the diagram in the OP above is a Supply Side Tap. Nothing wrong with that, in fact the breaker is then positioned to limit current and protect the inverter pass through to the 200A rating. Except that it does invoke the 120% rule if you are going to sell back. This is basically that the sum of the breaker rating + solar back-feed sell breaker cannot exceed 120% of the Bus Bar rating. Its gets a little more complicated with this type of double main breaker set up but if the bus bars are rated for 400Amps then each 200A breaker should be able to have a 40A solar sell back capability.

Attached is a picture of a panel similar to mine. Note the "guard" at the top where the meter hot lines directly feed the two 200A breakers. What would a "line-side" tap mean in this case? Does it mean the meter hot wires are pulled out through the top separately in to the polaris tap and then via the disconnect to the inverters? In that case, could I not feed the output of one of the inverters back into the 200A breaker and bus bar of my main meter-main panel (and not have a separate subpanel) as I originally thought I would need. Somewhat confused.

Yes

 

[garetwo]

Except that it does invoke the 120% rule if you are going to sell back. This is basically that the sum of the breaker rating + solar back-feed sell breaker cannot exceed 120% of the Bus Bar rating.

Also, are not most "400" amp residential panels rates at 320amps continuous? Will this impact the calculations? What model GE panel is it...duh (General Electric TM2440RMS)? I wonder what the feed through bussing is rated on the first 200 amp breaker - oh, according to AI it has the same 320 amp continuous as the main bus feeding the two main disconnects.

 

[garetwo]

what is a fused power distribution box with two 200-amp breakers?

 

[BentleyJ]

Also, are not most "400" amp residential panels rates at 320amps continuous? Will this impact the calculations? What model GE panel is it? I wonder what the feed through bussing is rated on the first 200 amp breaker.

I did attempt to look up the bus bar rating of that GE panel (model # given in original post) One place listed it as 320A and in another at 400 so I don't know for sure. There is most likely a label inside the panel that will clarify.

 

[garetwo]

I did attempt to look up the bus bar rating of that GE panel (model # given in original post) One place listed it as 320A and in another at 400 so I don't know for sure. There is most likely a label inside the panel that will clarify.

I believe it is a 320 continuous. Sadly, I am not an expert as many are in here, so I may have more questions than solutions. It seems you could feed the Sol-Ark panels directly, no polaris taps line side of the inverter and no manual transfer switches or the fused power box with two more 200 amp breakers on the load side. Aren't the inverters able to perform transferring and isolation?

 

[garetwo]

This is probably a great example of super ignorance, but why not have two separate systems and let the inverters control stuff, including zero export?

 

[ventura-diy]

Thanks for the replies everyone. To respond to your various questions (garetwo):
--my panel is a GE TM2440RMS (~15 years old)
--the "fused distribution box" (suggested by Sol-Ark engineer) could be a basic power distribution box capable of 400A (https://breakeroutlet.com/circuit-b...block-cat-69093-pdb-3-pole-by-ferraz-shawmut/) followed by two 200A breakers maybe installed in the subpanels themselves. The idea here is to combine the phase matched waveforms of both Sol-Ark inverters and basically recreate the 400A meter-main hot lines, except that in this case it will be max current output of the two sol-arks = 62.5x2 =125A total. Combining them (instead of feeding each Sol-Ark output separately to each panel) means you don't need to worry about the instantaneous load in any subpanel - it will all be fed by the combined inverters. By the way, wizards on this forum: is my understanding and explanation (and expectation) of this power combiner block correct?

I haven't thought through all the actual hardware items yet - that's something I'll pose to the forum wizards shortly. In the meantime, however, my immediate headache is about load-side vs line-side tap. My questions are in my next post.

 

[ventura-diy]

Pictures are worth a thousand words, so I've posed my questions about load-side vs line-side tap issue with my planned dual Sol-Ark setup in the attached picture.
I also noticed there is a similar thread on this forum about main-meter taps here: https://diysolarforum.com/threads/how-to-handle-meter-and-main-panel-combo.105734/
I'll post there referencing my same questions.
In the attached picture, I'm basically looking for some guidance as to what load-side tap would mean for me (trying to read-up /watch Youtube as much as I can about all the nuances about this set-up), since it seems like I can't do a load-side tap without spending $6K to replace my 400A main-meter combo unit (!!).

 

[ventura-diy]

In my previous post, I mentioned: "it seems like I can't do a load-side tap without spending $6K to replace my 400A main-meter combo unit (!!)"
I meant to say "line-side tap"

 

[garetwo]

--the "fused distribution box" (suggested by Sol-Ark engineer) could be a basic power distribution box capable of 400A (https://breakeroutlet.com/circuit-b...block-cat-69093-pdb-3-pole-by-ferraz-shawmut/) followed by two 200A breakers maybe installed in the subpanels themselves.

ok, thank you, the "fused" had me. I do think distribution with a main breaker is better than a whole new panel with more breakers

In my previous post, I mentioned: "it seems like I can't do a load-side tap without spending $6K to replace my 400A main-meter combo unit (!!)"
I meant to say "line-side tap"

You show only one existing 200 amp panel in your home and the addition of a new one, but I see you have a 2nd panel in the garage as well

• I have 400A service from SCE, fed via underground lines to a outdoor wall mounted 400A meter-main panel (General Electric TM2440RMS) with around 37 breakers used on the main panel and a subpanel (lug only) inside the garage with another 20 breakers used.
• I want to back-up everything (all circuits should have access to the battery backup power). So perhaps ~19 kW of panels on the roof and ~60 kWh of batteries. Solar charging and battery discharging must be shareable.

You only mention a quantity of breakers, no load calcs showing the two inverters will do a whole-home backup, I assume you are leaving the garage out? It "appears" a load-side tap would be ok, is there a reason you wish to do line-side?

You posted an image of a panel you said is like yours and asked:

Does it mean the meter hot wires are pulled out through the top separately in to the polaris tap and then via the disconnect to the inverters?

It does mean tapping load side of the meter, line side of the bus feeding the two 200-amp meters. Is it possible to have the utility kill power to the panel and open the left side to see if there is a provision in place already to tap onto the bus? Maybe someone in here has worked on them. I doubt field modifying a UL listed enclosure will be allowed. I think it was around 2020 the NEC mandated shielding the line side of the two 200 amp breakers, so a 15 year old panel may not have that shield in place - I cannot find any images online, it would be great to see yours.

 

[garetwo]

Pictures are worth a thousand words, so I've posed my questions about load-side vs line-side tap issue with my planned dual Sol-Ark setup in the attached picture.
I also noticed there is a similar thread on this forum about main-meter taps here: https://diysolarforum.com/threads/how-to-handle-meter-and-main-panel-combo.105734/
I'll post there referencing my same questions.
In the attached picture, I'm basically looking for some guidance as to what load-side tap would mean for me (trying to read-up /watch Youtube as much as I can about all the nuances about this set-up), since it seems like I can't do a load-side tap without spending $6K to replace my 400A main-meter combo unit (!!).

QUESTION 1: If I open up my panel, will I see the same “panel” at the top, i.e. the same breaker, where I could run a line to the existing lugs before they touch the 200A breakers, which means I won’t be able to do “line-side” tap for some reason? I do not think you will see the same shielding in a 15 year old panel, you can open the distribution side and look. If unsure, just turn off the two 200 amp breakers and you will may be exposed to live electrical on the line side only, none if there is a shield. I would ask SEC to kill the power and open the left side and get pictures so you see what you can do.

QUESTION 2: In my original drawing as shown, if I take the hot lines off the meter (i.e. 2AWG wires) to the 200A breaker, would this be considered a “load-side” tap? Well it certainly isn’t a main lug, so it’s not a main panel in the sense of the NEC. But it’s not a subpanel either. It’s an old subpanel meant to simply house a breaker for a previous main panel. In that case, is a “load-side” tap my only choice? What are the changes needed in this whole main-meter combo?

I do not think you have #2AWG to the line side of the meter, I think you will find there is a line side bus with compression lugs at the bottom that SEC has landed on, the meter socket, then a meter load-side, main breaker line side bus. A “main-lug” panel is one without a main breaker, you have two 200-amp breakers. A “sub-panel” is a load center or a panelboard (usually commercial). They are “subs” in the sense of being subject to the panel ahead of them. You must see the inside of the meter compartment AND have permission to tap into it.

QUESTION 3: If load-side is my only choice, what are the changes needed in my original diagram? What are the limitations, given that I’m planning two 50A–60A 10kW in parallel to power all the home circuits?

The Sol-Arks appear to have 200 amp feed through capability (my ignorance) but, unto themselves, only 50 amps continuous? So, when in “grid-down” the max output is dramatically reduced. I do not know enough about these to ensure no overloading the inverter(s) if you are feeding 200 amp loads.

 

[garetwo]

i would like to follow this if you moved it to a different thread, did you?

 

[garetwo]

• After much back and forth with a number of solar companies (and all kinds of misinformation), I've decided on a dual Sol-Ark 15K-2P system with the Renon Xtreme LV battery stacks

Will these be the system package or stacked modules?
Renon Xtreme LV Modular Home Battery System | 10.24–30.72 kWh | Stackable LiFePO4 | WiFi EMS | Plug & Play | 10-Year Warranty
Renon Xtreme LV 5.12 kWh Stackable Battery Module R-EM51100-XTL01

 

[glandpuck]

Ok, here is my free advice. Note, the thread is long, so i did not read all of it in detail. The initial diagram shows you have 400 amps of service, but really 2 independent 200 amp panels.

Just as a start, the 30 kW batteries are insufficient for a Sol-Ark 15k. That power is the minimum for each inverter. I have no clue about the brand of batteries you have chosen, however, I can tell you personally that Pytes batteries, available to you locally from distributor or Pytes sales will off you many choices and expandability as well as top notch quality. Please take a look at them.

My next point of concern is as follows: The initial line diagram shows a configuration that is just not going to work well. The Sol-Ark 15K wants a grid input and then a load output. The grid input should be a supply side tap after your meter and before your main 200 amp breakers. This can be with a Polaris tap or equivalent or via allowable lugs. The reason to do this is that when your grid is on, the Sol-Ark CT's are directional and will allow the inverter to feed back power to the grid which will really be into your circuits anyways. You can program the firmware to keep your batteries charged and send little to none of the PV power back into the grid. HOWEVER, THE MAIN ADVANTAGE OF A SUPPLY SIDE TAP IS THAT THE 120% BUS BAR RULE OF THE LOAD PANEL NO LONGER APPLIES AND IN FACT YOU CAN ACHIEVE UP TO 190 AMPS OF POWER BACK THROUGH THE TAP USING 90 DEGREE CENTIGRADE WIRE. IF YOU TAP ON THE LOAD SIDE OF THE BREAKER, THE 120% BUS BAR RULE APPLIES.

Now, on your load side tap, under the constraint of the 120% bus bar rule, the load output of the Sol-Ark will have to be a via a branch breaker into each of the 200 amp panels you created. This will be limited to a 50 amp breaker size and you need to de-rate your 200 amp breaker to 175 amps unless you have a 225 amp rated bus bar in the panel. The Sol-Ark can output 15kW using battery and PV or 12Kw using battery only (63.5A). BUT A 50 AMP BREAKER ALLOWS ONLY 40 AMPS OF CURRENT FLOW AT 240 VOLTS = 9,600 WATTS. SO YOU HAVE DRASTICALLY LIMITED YOUR INVERTER'S CAPABILITY. So when the grid is on, your Sol-Ark will send up to its max power rating back to your panel, but when there is no grid, you will be limited to 9,600 watts per inverter UNLESS YOU DE-RATE YOUR already de-rated 200 AMP BREAKER below 175 amps to 150 amps. Then you could install the load output of the inverter on a branch breaker of 80 amps and allow the full output of the inverter on the load side when the grid is down.

As for the batteries, if the inverter can output 12kW on battery and your battery is 30 kW and the DOD is 90%, that's 27 kW of useable power. In other words, a little over 2 hours per inverter at full load. Not enough unless you also have a generator running for backup. I suggest you start with 40 kW per inverter. Pytes V10/V16 or V5 stack or the LVi stacks will provide a solid pathway to the future expansion and work seamlessly with the Sol-Ark.

So in conclusion, I think you need to change things up a bit and rethink what you are doing. The manual transfer switches in you initial drawing are un-necessary unless you are switching power between the Sol-Ark and a generator and Sol-Ark and the grid to service the Sol-Ark. And at this point in time, in CA, the battery prices over time are a far superior value than a generator which needs oil changes, makes noise, needs service and is subject to rising fuel prices while the battery is paid for now and sits there for 20 years relying on the daily sun.

 

[ventura-diy]

Thanks for the replies, garetwo and glandpuck. The plot thickens...

• Yes, garetwo, I'll keep this community informed as I move forward. My timeline: hoping to talk to a licensed PE electrical eng within 1-2 weeks, hire him/her to draw up plans and submit to my AHJ and SCE before the Oct. is over. Trying to get first pass success, hence all this talk from me on this forum. I'm sure others in my area in SoCal have similar issues with 400A service (my neighbor, e.g.)
• The Renon Xtreme LV is stackable, floor mounted, indoor and outdoor rated. I'm considering either three 20 kWh stacks or two 30 kWh stacks (can't beat the price!) depending on what my AHJ says about where I can put them (inside or outside garage). EG4 LL-S will need outdoor enclosure if you can't get permission to put 60 kWh inside garage.
• Thanks for the detailed info glandpuck. Yes, I read up the 120% rule details and came to the same conclusion. Basically, it means I'm choking the Sol-Arks to 40A max, so no 200A passthrough from the grid to my loads when I might really need the extra power (but I can still max out to 62.5Ax2 if solar power and batteries are available right? I just can't feed more than 40Ax2 back to the grid to from the two Sol-Ark's right?)
• It all boils down to the line-side vs load-side tap. I must be able to do a line-side tap to really do justice to the Sol-Ark's capabilities

So, the big $64K question: how the heck do I do a line-side tap on my old GE TM2440RMS main-meter panel?

• SCE's suggested "Generation Meter Adapter" solution (https://www.sce.com/sites/default/files/inline-files/#126256_Generation+Meter+Adapter.pdf) does not seem to apply to me, since it is for 200A panels
• I can't just open up the panel and put in polaris taps on the main line (or can I?), because that seems to void the safety and code rules rated for these panels
• There seems to be an exception to the 120% rule for "center-fed" panels (rule 705.12(B)(3)(4), but my panel seems to be split-panel, and doesn't have a center bus bar.

So am I up a creek, with no choice but to do a panel upgrade if I want to do a proper line-side tap?

P.S.: There's no way I'm qualified to remove the dead front cover from my panel to take a look inside. My wife will kill me if I even try that, and then I'll die again from electrocution from the panel

 

[ventura-diy]

Will these be the system package or stacked modules?
Renon Xtreme LV Modular Home Battery System | 10.24–30.72 kWh | Stackable LiFePO4 | WiFi EMS | Plug & Play | 10-Year Warranty
Renon Xtreme LV 5.12 kWh Stackable Battery Module R-EM51100-XTL01

It'll be stacked modules. They can go inside or outside have a nice relatively simple floor mounting mechanism, so no expensive wall mounting headaches. Also you can stack up to 20 kWh per stack (seems to be the AHJ allowed limit per stack for inside garages in SoCal) or up to 30 kWh per stack max - about 5.5 feet high.
The Pytes batteries also look good and seem similarly priced for 60 kWh, as glandpuck mentioned. However, they will need some sort of weather rated enclosure, maybe mulitiple ones, if you want to put them outside (e.g. V-BOX-OC).

 

[ventura-diy]

i would like to follow this if you moved it to a different thread, did you?

Still continuing on this thread for now. If it gets too long, I'll branch off to a new thread (to focus on a specific issue).

 

[garetwo]

P.S.: There's no way I'm qualified to remove the dead front cover from my panel to take a look inside. My wife will kill me if I even try that, and then I'll die again from electrocution from the panel

The dead front is not a huge issue, but I am pretty sure if you contacted your utility and told them you would like to have your service shut down to inspect it, the line person coming out will open both sides up for you because they are typically way more helpful than the office staff. Comes out, shuts down, pulls meter, opens the left side, you take a picture or two, you ask him to open the right side whare the two screws have been somehow already removed....Provide the images to the forum! Or, even you are more than safe to remove the dead front because the entire assembly is dead.