35,000 SF Commercial Office Building

[HarryN]

I wonder if you might be better off with a commercial grade setup - such as ones that are used by the companies that do grid scale solar fields?

Something like an ABB or GE that feeds higher voltages directly to the transformer.

https://new.abb.com/solar

 

[wpns]

I wonder if you might be better off with a commercial grade setup - such as ones that are used by the companies that do grid scale solar fields?

Something like an ABB or GE that feeds higher voltages directly to the transformer.

https://new.abb.com/solar

Now you are on the wrong side of the meter, getting paid wholesale rates for all of the power you generate while simultaneously paying retail rates for your consumption.

 

[mciholas]

Hardly a "direct competitor". SMA invented the grid-interactive PV inverter. Also the transformerless grid-tie inverter.

I didn't see any particular capability the SMA had that the Growatt lacked, at least not what I would need it to do.

Is your statement about what you perceive as a quality difference or is there some function the SMA does that the Growatt doesn't do, that I would need?

Mike C.

 

[Hedges]

Actually more likely the Growatt has more features.
And more likely you'll find documentation on them (sad how far the market leader has fallen - SMA used to provide extensive documentation.)

Just that I think SMA has far and away superior quality to any of the Chineseum inverters.
Now, if a tier-1 company has manufacturing done in China by a leading manufacturer, and monitors them for quality, I'm sure it can be top notch.
But a Chinese brand competing on price in the US, well, search the forum and see if people are having issues.
Perhaps some will turn out to be market leaders with quality as well.

I've used older model SMA PV and battery inverters. I ran up to 5 Sunny Boys for 17 years, had a couple failures, calculated something like 34 years MTBF. For now I'm mostly using SB 5000US and SI 6048US series.

I'm now playing with Sunny Boy Storage connected to LG RESU-10H batteries and have some issues. Getting some support. Don't know how Sunny Boy Smart Energy will be, was expecting to install a couple, but may have picked up enough Sunny Boy -41 series to use those instead (unless somebody wants to add storage, which isn't urgent with our NEM 2.0 reservations.)

 

[mciholas]

But a Chinese brand competing on price in the US, well, search the forum and see if people are having issues.

Is any inverter brand issue free?

Without knowing how many of each brand are installed, it is hard to convert the issue count to a problem rate. The cheaper inverters may be installed more often leading to a false sense of high failure rate.

Obviously, I don't want problematic inverters, so finding ones that do the job reliably with good value is hard to do.

My present question is whether it works to take 3 208 VAC single phase inverters and wire them to a 3 phase grid in a delta (inverter #1 feeds across phase A & B, #2 across B & C, #3 across A & C). That feels like that should work, but I'd like confirmation of it.

Obviously, a purpose made 3 phase inverter will work, but those are rare and seemingly significantly more expensive.

Mike C.

 

[Hedges]

I think SMA and Fronius have very good track records, but I'm not involved enough in the industry to really know. Some other big name brands have stood out for failure rates. I understand SMA was problematic for a while, like AFCI nuisance tripping. And then RSD function being only partially compatible with Tigo. Sunny Boys were used in a lot of solar farms.

By the way, lots of people are happy with SolArk. That is built in China, supported in US. But it is a more expensive AIO with backup/offgrid features, things you won't want to pay for.

I have no specific knowledge regarding Growatt. Another brand, I've read through many threads on issues. Part of that was people trying to use European single phase models for split phase, and the "supported" approaches didn't seem safe and correct to me.

In general, yes, 208V inverters will work between two legs of 120/208Y, and 240V inverters for the various delta arrangements.
Some of my Sunny Boys work with 208, 240, and 277V. They can be configured by jumpers, or auto-configure when neutral is connected.
Almost certainly an 208V inverter expects that situation.

Capacitance of PV panels matters when used across legs of 3-phase. Unlike 120/240V split phase, the midpoint of 208V orbits around ground at 60 Vrms, so capacitance shows up as leakage current. Most panels should be OK, some funny technologies are a problem.

3-phase inverters, by the way, often require a neutral. Some will work with delta, but not the higher voltage to ground of a corner grounded delta (which can occur with a fault.) And using transformers with them can be problematic. I did get a 277/480Y (or 480 delta) inverter working with 120/208Y battery inverters, but with a few tricks. SMA didn't offer a 120/208Y inverter. Their 277/480Y inverters are pretty economical for the wattage. Their European models are better matched to each other.

Unfortunately a well-behaved transformer to use with the following inverters costs too much. Need an HF inverter designed for your voltage.

Discover Sunny Tripower CORE1 String Inverter | SMA America

Discover the world's first free-standing string inverter: Sunny Tripower CORE1 ► Faster installation ► Rapid shutdown compliance ► SMA Shadefix

www.sma-america.com

https://www.sma-america.com/products/solarinverters/sunny-highpower-peak3

Somebody here named a 3-phase 120/208Y grid-tie inverter but I can't find the posting now.

 

[mciholas]

I think SMA and Fronius have very good track records

Will look at them. Thanks for the pointers.

I have no specific knowledge regarding Growatt.

I am currently trying to figure out if their US split phase units (example MIN10000TL-XH-US) will work on the delta 208 VAC 3 phase power I have. They show L1, L2 and N connections, and the N will not be stable between L1 and L2 (60 VAC wander as you noted) due to the 120 degree phase shift. N and PE will be stable, however, since they are bonded at the main panel.

In general, yes, 208V inverters will work between two legs of 120/208Y

Before committing to that, I would want a wiring diagram from the inverter maker showing it can be wired that way. The wandering N concerns me. Maybe that's is a non issue, or maybe it is fatal. I have emailed Growatt to ask about this.

A hopeful sign is that the Growatt units for the US market have 208 VAC numbers in them (somewhat derates their power output versus 240 VAC), and the only reasonable way you get that is by touching two phases of a 3 phase system. So there must be a way to use them that way or why would they give both 240 VAC and 208 VAC numbers?

Some of my Sunny Boys work with 208, 240, and 277V. They can be configured by jumpers, or auto-configure when neutral is connected.

Interesting.

Capacitance of PV panels matters when used across legs of 3-phase. Unlike 120/240V split phase, the midpoint of 208V orbits around ground at 60 Vrms, so capacitance shows up as leakage current. Most panels should be OK, some funny technologies are a problem.

It would take a lot of capacitance to make meaningful current at 60 Hz. At 100 nF (way more than one would expect), at 60 VAC wander, looking at 2.2 mA RMS current. Not a big deal.

3-phase inverters, by the way, often require a neutral.

I have a neutral. 208 VAC 3 phase wye. A "proper" 3 phase inverter is an option, but seemingly less choice and not as cost effective. Also, if I put in 6 Growatt single phase units and lose one, I don't lose the whole array. Also, having a spare inverter is cheaper if it is a smaller single phase unit.

Somebody here named a 3-phase 120/208Y grid-tie inverter but I can't find the posting now.

SolarEdge has something, SE50KUS.

https://knowledge-center.solaredge.com/sites/kc/files/se-three-phase-inverter-with-synergy-technology-208v-datasheet-na.pdf

Main bug is that is requires SolarEdge optimizers at each panel. Apparently, it can't work without them, perhaps the units rely on the optimizer for MPPT functionality. Those units appear to be ~$100 per panel, which is budget busting. I'm really trying to avoid MLPE boxes if I can, just extra parts, connections, failure points. I also don't like the everything in one box architecture if I can help it.

Ideal for me is a cost effective grid tied 208 VAC inverter in the 6 to 12 KW class that will drive 2 phases of a 3 phase system.

Mike C.

 

[Mike 134]

Will look at them. Thanks for the pointers.


I am currently trying to figure out if their US split phase units (example MIN10000TL-XH-US) will work on the delta 208 VAC 3 phase power I have. They show L1, L2 and N connections, and the N will not be stable between L1 and L2 (60 VAC wander as you noted) due to the 120 degree phase shift. N and PE will be stable, however, since they are bonded at the main panel.


Before committing to that, I would want a wiring diagram from the inverter maker showing it can be wired that way. The wandering N concerns me. Maybe that's is a non issue, or maybe it is fatal. I have emailed Growatt to ask about this.

A hopeful sign is that the Growatt units for the US market have 208 VAC numbers in them (somewhat derates their power output versus 240 VAC), and the only reasonable way you get that is by touching two phases of a 3 phase system. So there must be a way to use them that way or why would they give both 240 VAC and 208 VAC numbers?


Interesting.


It would take a lot of capacitance to make meaningful current at 60 Hz. At 100 nF (way more than one would expect), at 60 VAC wander, looking at 2.2 mA RMS current. Not a big deal.


I have a neutral. 208 VAC 3 phase wye. A "proper" 3 phase inverter is an option, but seemingly less choice and not as cost effective. Also, if I put in 6 Growatt single phase units and lose one, I don't lose the whole array. Also, having a spare inverter is cheaper if it is a smaller single phase unit.


SolarEdge has something, SE50KUS.

https://knowledge-center.solaredge.com/sites/kc/files/se-three-phase-inverter-with-synergy-technology-208v-datasheet-na.pdf

Main bug is that is requires SolarEdge optimizers at each panel. Apparently, it can't work without them, perhaps the units rely on the optimizer for MPPT functionality. Those units appear to be ~$100 per panel, which is budget busting. I'm really trying to avoid MLPE boxes if I can, just extra parts, connections, failure points. I also don't like the everything in one box architecture if I can help it.

Ideal for me is a cost effective grid tied 208 VAC inverter in the 6 to 12 KW class that will drive 2 phases of a 3 phase system.

Mike C.

You'll need something if it's a roof mount to shutdown each panel. Either optimizers or Tigo units...........

 

[mciholas]

You'll need something if it's a roof mount to shutdown each panel. Either optimizers or Tigo units...........

Not clear I do. Indiana is using NEC 2008 presently which doesn't have RSD.

Later NEC (2023?) allowed for UL 3741 which doesn't need per panel RSD, either.

So I need per panel RSD only if I get sandwiched in a brief period of time on code compliance.

In any case, Tigo TS4-A-2F is a lot cheaper per panel than the SolarEdge commercial optimizers and I can choose various brands and not be locked to one vendor. This is what turned me off of the SE50KUS unit. If I am going to have that much electronic stuff on the roof, I might as well do micro inverters. Sigh.

Mike C.

 

[Quattrohead]

Do you need 3 phase for anything ? Single/split is obviously easier to deal with.
I have 45 Solaredge optimizers and a 10k wave inverter you can have for $1000 plus actual shipping

 

[mciholas]

Do you need 3 phase for anything ? Single/split is obviously easier to deal with.

For my size building, the utility only does 3 phase.

To rewire the building to split phase would be exceedingly costly in any case.

We have maybe 2 things that are truly 3 phase (like a large temperature chamber).

I have 45 Solaredge optimizers and a 10k wave inverter you can have for $1000 plus actual shipping

I'm not to the point of buying stuff yet.

Mike C.

 

[Mike 134]

Not clear I do. Indiana is using NEC 2008 presently which doesn't have RSD.

Later NEC (2023?) allowed for UL 3741 which doesn't need per panel RSD, either.

So I need per panel RSD only if I get sandwiched in a brief period of time on code compliance.

In any case, Tigo TS4-A-2F is a lot cheaper per panel than the SolarEdge commercial optimizers and I can choose various brands and not be locked to one vendor. This is what turned me off of the SE50KUS unit. If I am going to have that much electronic stuff on the roof, I might as well do micro inverters. Sigh.

Mike C.

I just read the the 2023 NEC sec 690.12 and only 2 exceptions do not require RSD. However as you mentioned if you go to the expense of meeting UL 3741 standards such as the Ironridge system with the inverters they spec. it can be done

https://files.ironridge.com/flat-roof-mounting/resources/brochures/IronRidge_BX_System_UL3741_Installation_Addendum.pdf?_gl=1*1q8400c*_ga*MjA2NjE0MzM1Ni4xNzA4NTM1MDkz*_ga_TQ45KDFH4R*MTcxMDczMTk2Ni4yLjEuMTcxMDczMjA0MS42MC4wLjA.*_ga_QQSG9360JJ*MTcxMDczMTk2Ni4yLjEuMTcxMDczMjA0MS42MC4wLjA.

 

[Ryushin]

I've been reading through the thread. I am impressed with the custom design of your building.

I was looking at the Sol-Ark 30K manual and how it's different than the Sol-Ark 15K. It's an impressive design and it's interesting that they went with a high voltage DC setup for batteries. Though I think dual Sol-Ark 15Ks might offer more flexibility.

I'm thinking that since you can sell excess energy .25 to 1, you can have a large PV arrays to cover all your usage during the day, charge up your batteries, and sell big power to the grid. Then use the batteries to peak shave for the night and cloudy days to remove/flatten the demand charge.

My thinking was to use two Sol-Ark 15Ks in a 3 phase setup, four Growatt MIN 11.4K for AC Coupled into Sol-Arks, 70kW of PV, 100kWh of battery.
Either way, very much enjoying the possibilities of what you are trying to do.

 

[12VoltInstalls]

very much enjoying the possibilities of what you are trying to do

Totally agree.
This scale is nowhere in my wheelhouse nor does knowledge/experience specifically apply in particulars but from the original post my attention was captured because it had a tone of confidence and competence with the questions.
So many new, long, posts are replete with nonlinear questions that wouldn’t even need to be asked if they’d taken the time to actually be introspective and plan a little bit. And then the questions that come are an intelligent process of learning- the basis of decision-making.

I’m learning a lot here and feel like I should be paying a fee to audit the class.

 

[wpns]

peak shave

His peak demand charge isn’t the low hanging fruit, IMHO, I’d ignore it.

 

[Ryushin]

His peak demand charge isn’t the low hanging fruit, IMHO, I’d ignore it.

Well, @mciholas said the demand charge in his first post is a significant part of his bill so I thought it would be important to mitigate it:

We pay a "demand charge" which is a significant part of our bill. It is a charge per KW for the highest demand we've had in a 5 minute period in the last 3 months. So if by chance all the HVAC units line up and we're running a big machine (the test temperature chamber is the biggest load we got at about 5 KW), we can peak up and that costs us money over a long time.

At least with grid shaving there should be more of a flat charge from that point on.

 

[mciholas]

Well, @mciholas said the demand charge in his first post is a significant part of his bill so I thought it would be important to mitigate it:

I was a bit premature on that. Further research showed it to be under 10% of my bill. Something, but not huge. It wouldn't be worth a huge battery bank just to shave that cost. At best, I would trim off maybe 5-7 KW. My demand charge is $5.111 per KW in excess of 10 KW for the peak 15 minutes of demand in the month. My demand power is usually 22 to 32 KW, so that's $60 to $110 per month.

Based on feedback here, the idea of just building a large array with no battery is my current trajectory. My usage is about 300 KWH per day, so an array of about 100 KW would probably bring my bills way down but not near zero for sure. According to PVWatts calculator, that would generate about 121 MWH per year and I use about 108 MWH.

The problem is I pay 100% for import and get paid 25% for export. Even an array of that size won't zero my bill, it would have to be even larger, maybe 200 KW, to get close. The pay back for this is starting to be unreasonable as that would be at least a $100K array.

If I add battery to the design and aim for near zero export (try to use power locally first), then I can have a smaller array (about 80 KW) but I need a lot of batteries. With daily 300 KWH needs, that is about the size of the battery I would require. If we assume $200 per KWH for batteries, that's $60K just for those and they age out eventually. Having that much battery does give me backup power, a "generator", which is a nice feature but not all that compelling (only a fraction of the building would be on backup due to the complexity of wiring into a 288 KW service). I'd still have to rely on the grid for cloudy days, and my demand charge would likely be similar since my peak demand will occur on those days.

As a pure economic play, it can be hard to justify this system. I'm still working the numbers. Low cost panels ($100 for ~400 watts) plus low cost single phase string inverters (Growatt 10K for $1300) might make it work, but it would be going for the cheapest parts.

Mike C.

 

[Ryushin]

Based on feedback here, the idea of just building a large array with no battery is my current trajectory. My usage is about 300 KWH per day, so an array of about 100 KW would probably bring my bills way down but not near zero for sure. According to PVWatts calculator, that would generate about 121 MWH per year and I use about 108 MWH.

The problem is I pay 100% for import and get paid 25% for export. Even an array of that size won't zero my bill, it would have to be even larger, maybe 200 KW, to get close. The pay back for this is starting to be unreasonable as that would be at least a $100K array.

As a pure economic play, it can be hard to justify this system. I'm still working the numbers. Low cost panels ($100 for ~400 watts) plus low cost single phase string inverters (Growatt 10K for $1300) might make it work, but it would be going for the cheapest parts.

I can see where you going for sure. My two Growatt MIN 10K has been working great for me. The Growatt MIN let you combine 31 of them together. So those Growatts and inexpensive giant 550-750W panels. Might be best to order directly from China to get the best price. I directly ordered my 550W Bi-Facials from Bluesun during the summer for the best pricing I found at the time and they shipped them from the LA warehouse.

 

[Quattrohead]

And those peaks are due to multiple AC units turning on at once so a few ESP devices set up to make sure that cannot happen via the thermostats would mitigate that.
I agree with your cost and return analysis, I did the same for my new home build and it is absolutely not worth it for me to do, but I am doing it because I can build it into the cost of the home and I can do it and I want to do it. Battery backup is very nice in a hurricane area and not relying on FPL is cool even though their rates are very reasonable. And a little piece of me feels high and mighty and green lol

 

[12VoltInstalls]

And those peaks are due to multiple AC units turning on at once so a few ESP devices set up to make sure that cannot happen via the thermostats would mitigate that.

Exactly.
And even just 20kWh batteries might help partner with management to suppress peaks enough that they pay for themselves in a coupla years of a 15yr+ lifespan?
Just how I think…