2x Sol-Ark 15K's + HomeGrid Stacks

[2TrevorJ]

After 1-1/2 years of planning I'm roughly a week and half into my new setup. 2x15Ks - 57.6 kWh of HomeGrid Stacks - 20.4 kW of REC's w/ Tigo TS4-A-O Optimizers and Cloud Connect Advanced (CCA) - Bypass/Transfer Switch - MicroAir Easystarts on my 3.5 & 4-ton AC units. Big house draws are pretty much all gas (other than the oven and my daughter's Nissan Leaf) so I have quite a bit of power to spare right now, but July & August should be close if my math holds out. So far this has handled everything I've thrown at it with zero compromises. There's actually a screen shot from this morning with me charging the batteries, the car, and exporting all at once. ? The only disappointment so far has been the lack of 600A charge limit from the Homegrids when they prominently advertise 300A for each stack. Most of the time the BMS is calling for 200-240A (total). Super conservative at <= 0.2C. That said, I've barely ever run into the charge limit and started exporting on PV. I was at 100% yesterday at 17:15, 79% at dawn this morning, and was topped back off and exporting by 10:40. ? Now, before anyone mentions it...yes this was an expensive endeavor that doesn't make a whole lot of sense if all you're after is ROI. That's not my focus. Feel free to ask any questions about the system/performance/behavior.

 

[Danke]

Very nice !

Did you go with two 15Ks for redundancy?

 

[2TrevorJ]

Did you go with two 15Ks for redundancy?

EV charger and two A/C units gave me pause with a single 15K. That and both A/C units/thermostats take cues from a single app and if/when I manually drop the temp the compressors fire up at exactly the same time. I'm not sure a single 15K can take that hit...even with soft starts. It might as I'm seeing 32-34A on the 4-ton and 16-18A on the 3.5-ton but I didn't have that data when I modeled the system.

Secondary is having the ability to charge the batteries at >275A but so far that's proven to not be that necessary. I've got 14.2kW of excess power as I type this; 272A at the HomeGrid's 52.2V indicated (if the batteries weren't already pegged). Maybe I'll see more in the summer but the extra charge current is a nothingburger right now.

 

[Hedges]

I picked up about 8kW of REC 325W and Tigo "Fire" RSD. Plan to use with a transformerless TriPower inverter.

I'm going to be curious how your optimizers behave with half-cut cell panels. I think they are internally wired as 2p3s.
Without optimizers, a better MPPT algorithm can run voltage down and see if there is a higher wattage peak at lower voltage, pushing current through bypass diode where one section is shaded.

I have no idea how the RSD deal with parallel/series PV. But I doubt they periodically sweep the voltage range.

One of the guys here posted a link to data on portal showing Tigo's report of extra power captured. But I don't know if it can really know how the array would have performed without optimizer. I figure a single shaded sectio of 2p3s could get Tigo to double current from 3s (if "double" is within its operating range) and declare victory, not realizing there was 2p2s available with 33% more power.

Maybe if you log an optimizer's reports while experimenting in covering one cell in each of 1 ... 5 sections, various configurations.

 

[Rayh76]

Great looking install. Thanks for sharing. I can't quite tell but did you use 2/0 wire downstream of your PDBs back to your transfer switch and then to your main panel? I have 2 Solark 15ks still in the box in my garage and I'm hung up on if that wire should be rated for 200amp or 400amp. The breakers on each Solark is 200amp so the combined should be 400amp but I also know that the breaker at my pole downstream of the meter is 200amp. Theoretically it should be impossible for the combined solark load wire to reach that amperage. I'm curious to how others are handling it. I commented on Engineer775 latest video asking the same question but no reply yet. Thanks!

 

[2TrevorJ]

L1/L2/N everywhere is 2/0 copper. I ultimately came up with the same answer as you (as evidenced by my install config) but I'm not without concern. Is it possible to draw say...160A continuous from the grid then supplement it with PV/battery to meet a load beyond 200A? I bet it is. I've lived here in this new house with no issues for 16 months on a 200A breaker so I'm not too concerned with my current load profile BUT I'm not going to be adding additional load to my main panel without some additional thought and measurement. Good thing I have a whole house load-meter built in now. I can't imagine seeing 38+kW load. My record so far is 11kW.

 

[Rayh76]

Thanks! I'm guessing Eng775 came up with the same conclusion as it looks like he used the same size SER aluminum wire everywhere also (I could be wrong).

May I ask where you purchased your PDB's from? Are those Mersen's?

Thanks again,
Ray

 

[Rayh76]

The more I stare at your photos the more questions I have. What size/model wiring trough are you using? I've never considered having zero clearance between the trough and the inverters. Looks much cleaner and I wonder why no one else is doing that? Is your trough spaced away from the wall? If not too much of a hassel, a picture of the side would be helpful for me.

 

[629658]

The more I stare at your photos the more questions I have. What size/model wiring trough are you using? I've never considered having zero clearance between the trough and the inverters. Looks much cleaner and I wonder why no one else is doing that? Is your trough spaced away from the wall? If not too much of a hassel, a picture of the side would be helpful for me.

12” trough sits on the wall

 

[Rayh76]

A 12" trough butted up to the solarks gives it 0" of clearance and blocks the vent holes. I don't think Trevor's are blocking the vents.

 

[2TrevorJ]

They're CMC Brand "CDA-355" blocks that they got from Grainger. I went looking for a link to them and they're MIA. The installer was less than enthused by the $200 a piece price they paid to get them quickly after they failed to pay attention to the parts list I sent them in advance. In hindsight they should have just picked up a pair of these:

https://www.grainger.com/product/MERSEN-Power-Distribution-Block-3-25CC40

https://www.grainger.com/product/BUSSMANN-Power-Distribution-Block-3-4XK20

The side view isn't pretty and my first thought when they unloaded that trough was "WTH...where's the 12" trough?" but Ray's correct...it breathes really well.

Solar comes in a separate conduit on the end towards the batteries. And excuse those exposed low voltage wires. That's the 48V to 24V DC-DC power supply wires for the Tigo Cloud Connect Advanced unit in the trough. The CCA (and therefore the solar array) always has power if the batteries are alive. The rapid shutdown stops the party if necessary (the inverters first which then kills the CCA via normally closed relay). Another thing I figured out for the installer. Don't get me wrong, nice folks with sound basics...just not versed in a whole-home backup like this. I've had the luxury of geeking out on the minutiae for quite a while.

 

[Rayh76]

Thanks for the quick reply and photo. That's what I had envisioned in my head. Now I need to decide how I'm going to mine...so many decisions. Haha

 

[Rayh76]

Are your CTs upstream of you PDB box or are you not using them? I think I see the wires passing through but curious to why they aren't in that box.

 

[Browse]

The manual says minimum of 6" vertical clearance, but I don't see any fans in the bottom section of the unit, so not sure if that applies to just the top...

 

[2TrevorJ]

Are your CTs upstream of you PDB box or are you not using them? I think I see the wires passing through but curious to why they aren't in that box.

CT's between the meter and the 200A breaker. Barely fit in the breaker box. Had to extend them a bit with Cat5 twisted pair and that worked like a champ...just pay particular attention to the diagram in the Sol-Ark manual when you do the extension and connection at the master. Get a crimper like this to terminate the Cat5 pairs at the master:

https://www.amazon.com/Preciva-Hexagonal-Self-adjustable-Terminals-Connectors/dp/B07XBLGPCY/

Super clean. Ran the CT cal afterwards in the Sol-Ark and it worked just fine. I really don't think they're necessary with my config but whatever...they were in the box. ?

The manual says minimum of 6" vertical clearance, but I don't see any fans in the bottom section of the unit, so not sure if that applies to just the top...

Intake is at the bottom back of each unit and air flows goes vertical from there out the top.

 

[Danke]

The manual says minimum of 6" vertical clearance, but I don't see any fans in the bottom section of the unit, so not sure if that applies to just the top...

It doesn’t say left or right side either…

“2” Minimum Horizontal Clearance || 6” Minimum Vertical Clearance”

Bottom:

 

[niktak11]

The manual says minimum of 6" vertical clearance, but I don't see any fans in the bottom section of the unit, so not sure if that applies to just the top...

It's 6" both top and bottom

 

[Rayh76]

Trevor,
Since I over think everything...
The manual states (pg 39) that CTs should be installed upstream of everything except for a Gen transfer switch, knife blade disconnect, etc. I've added (on paper) a separate PDB so that I could install the CTs downstream of the connection going to the knife blade disconnect. My drawing is attached. I'm not sure how your Solark will act if you throw the knife disconnect but maybe depends on settings. I was hoping to save money by only having 2 PDBs (or fewer Polaris lugs) after seeing your setup but to comply with the manual I might need 3. Not sure but I sure do appreciate this discussion.

Ray

 

[Danke]

https://diysolarforum.com/attachments/back-of-trough-jpg.133236/

I have not installed mine yet and have not thought about doing it that way, but it would sure save both space and materials.

Anyone know if there’s any codes that need to be complied with for clearance of wireway to inverter?

 

[Rayh76]

Something to consider is inverter maintenance. If I'm seeing everything correctly, the trough is supported by both inverters. What would he need to do if one inverter needed removed? Temporarily support is from below? Add some big shelf brackets underneath?