2 Systems tying to one main panel: eg4 18k pv + IQ7+

[zanydroid]

Could use optimizers for shading, but also some debate that the built in diodes do just as good of a job as an optimizer or microinverter with regard to shading. Obviously, RSD is required for rooftop systems have to consider that.

Trading microinverters for the the bad interoperability (if SolarEdge, maybe also the new SolArk ones) and lack of forum experience of optimizers is not my jam.

 

[zanydroid]

Doesn't Luxpower make this inverter?

Yup, makes it more disappointing if true, though if folks asked maybe they can port over some code.

The LuxPower AC coupled battery inverter does not have MPPT, it is targeted for retrofit only on an existing grid tie system, to add self consume and TOU optimizing. IIRC it can’t charge from/turn on the microinverters when off grid, so the opposite problem. So it’s more of emergency power for short outages.

I won't disagree with the lower end inverter comment.
I expected the inverter to charge from AC coupled solar. I wasn't looking for that info, so I didn't see that hole in the instructions. In my reading I think it would charge from AC coupled solar when off grid. That's why there is an end SOC. Once the battery is charged to 100% there's no where else to put the energy from the AC coupled solar.

It will charge from off grid by my reading. And the bunch of UI settings they screenshotted sort of double confirms it.

Take a look at the two paragraphs for on-grid though, it makes no such promises.

 

[zanydroid]

No statements about charging behavior and no UI showing ways to customize it.

 

[the.shining]

Can you draw it out? Which way is down stream? When you say regulate, is this with grid connected or not?

the hybrid is downstream from the microinterter because it receives the microinverters output as its input.

They also don't have the long history and track record of Enphase, so longevity is still a question in my eyes.

Yes, dependability is a big asset, but micorinverters I'm general appear to have less issues with failure rates because they are simpler machines which is one big reason to build with micros, any brand.

It can't. In the main panel frequency is set by the grid, no inverter is going to influence grid frequency. When disconnected from the grid, then the battery inverter sets the frequency for your home micro grid.

on grid: if batteries are full, no load is present, and micros are outputting pv, the eg4 needs to be able to shutoff micros. This can't be done by frequency shifting. BUT, there may be an alternative relay control mechanism. IF an alternative exists, then no other solutions need be entertained. Otherwise, Hoymile may be the answer.

Off grid: frequency shifting can certainly be implemented. No problem here for eg4.

I could be wrong and I haven't read the manual cover to cover, which I'd suggest you do before purchasing an inverter, but this section sure does look like it is documented.
View attachment 184937

This section dismisses Frequency Shifting as a regulating mechanism when ON GRID. It doesn't explicitly rule out other alternative relay control (regulating) mechanisms. It's likely safe to assume there is no alternative...thus Hoymiles are the defacto alternative

 

[zanydroid]

Yes, dependability is a big asset, but micorinverters I'm general appear to have less issues with failure rates because they are simpler machines which is one big reason to build with micros, any brand.

I am not sure they are simpler. They’re passively cooled in a more inclement environment. I would guess they are more complex than a grid tie string inverter.

This can't be done by frequency shifting. BUT, there may be an alternative relay control mechanism. IF an alternative exists, then no other solutions need be entertained. Otherwise, Hoymile may be the answer.

What I was looking for was some discussion about implementing zero export/self consume against the current output of the microinverters. This is certainly doable by turning on the charger and modulating it until the net power is zero.

 

[k490]

If that was the case, why are nearly every battery inverter in this class designed with pass through relays, grid forming, etc?

Sure, energy arbitrage is a valid use case (one that I employ), but I don't think this is the most common set up.
That's a lot of work and expense to not have grid down back up power.

You can have both, I do.

Yes, I agree it can pass through but you're not going to have 100% of your home's circuits on the critical load backup panel. If you move everything over to that sub panel might as well just go with an off-grid inverter which isn't exactly true, the off-grid inverter does have a grid input. The only difference with a hybrid is it can back-feed to that grid input where an off-grid inverter can't. I think I was kind of talking about a way which gives the homeowner the ability to permit a string of microinverters then later add a DIY inverter / Battery which you can expand.

 

[zanydroid]

Yes, I agree it can pass through but you're not going to have 100% of your home's circuits on the critical load backup panel.

This is exactly the setup that you pay a premium for on the SolArk 15k and EG4 18kpv. As long as you have all your home circuits on 200A or smaller service you can splice the inverter in between the 200A subpanel with all house loads and the meter/main combo. These have an internal 200A bypass / transfer relay.

The only difference with a hybrid is it can back-feed to that grid input where an off-grid inverter can't. I think I was kind of talking about a way which gives the homeowner the ability to permit a string of microinverters then later add a DIY inverter / Battery which you can expand.

Technically many POCO will also require the battery to be permitted if the storage inverter is to be paralleled with grid (IE any kind of grid assist mode). It’s stipulated in the interconnection rules for almost all California POCOs. Either you try to fly under the radar, set up an inverter that can carry full system load from battery and inverter, or pull off a few circuits into a CLP/the only circuits legally allowed to self consume.

 

[FilterGuy]

I really don't see a good reason to even use the microinverters if you want to permit entire system.

The main use case for Micro-inverters with the 18Kpv is when the customer has an existing grid-interactive solar system that they want to add batteries to. Rather than re-wire the array, you can just take the AC out from the existing system and feed it to the correct port on the 18Kpv.

Yes, dependability is a big asset, but micorinverters I'm general appear to have less issues with failure rates because they are simpler machines which is one big reason to build with micros, any brand.

Micro Inverters have a terrible reputation for having a High failure rate. (All of them, but particularly EnPhase).

1) They are sitting under the hot panel and heat is not good for electronics.
2) You have a lot of them, so even if the absolute failure rate is low, you have to multiply that failure rate by the number of them you have for the failure rate of one of them going out.

 

[zanydroid]

2) You have a lot of them, so even if the absolute failure rate is low, you have to multiply that failure rate by the number of them you have for the failure rate of one of them going out.

That just yields the expected number that will die. I wouldn’t say this is worse than a string inverter since it is still incremental where a string blows up all at once (albeit it also restores all at once… note that RSD for strings are connected in series and they themselves can degrade reliability) . Arguably progressively losing microinverters could be considered a cost of doing business just as panel level degradation is.

They are parallel wired so if they fail the rest will stay up, unless the failure also breaks the disconnect/isolator between the AC output and trunk and wrecks the whole branch.

 

[zanydroid]

The main use case for Micro-inverters with the 18Kpv is when the customer has an existing grid-interactive solar system that they want to add batteries to. Rather than re-wire the array, you can just take the AC out from the existing system and feed it to the correct port on the 18Kpv.

Do you know if 18kpv properly factors in the output of microinverters in on-grid self consumption mode? The manual suggests it does not, which is surprising because other Luxpower products can do it, and clearly says it in their manual.

 

[k490]

The main use case for Micro-inverters with the 18Kpv is when the customer has an existing grid-interactive solar system that they want to add batteries to. Rather than re-wire the array, you can just take the AC out from the existing system and feed it to the correct port on the 18Kpv.

Micro Inverters have a terrible reputation for having a High failure rate. (All of them, but particularly EnPhase).

1) They are sitting under the hot panel and heat is not good for electronics.
2) You have a lot of them, so even if the absolute failure rate is low, you have to multiply that failure rate by the number of them you have for the failure rate of one of them going out.

I have heard that EnPhase can be a problem trying to get it to AC couple to an inverter. Also have a limit how much PV power you can AC-couple. Why I was saying just leave it tied into the main panel and setup an inverter battery back feed the same main panel. Obviously would need to make sure the busbar can a handle the amount of current. I understand would lose that string if power went out could also connect more panels to the 3 MPPT inputs of an 18PKV.

 

[the.shining]

Enphase provides 25 warranty on their microinverters. Eg4 provides 10 yr warranty. Whether these warranties can be depended on is anyone's guess, but all else being equal, enphase microinverters appear to be the cheaper and longer life inverter at the present time.

And it sounds like the original system I proposed with the microinverters feeding into the main panel (instead of the eg4) could be feasible for ON grid AND OFF grid (using some relay system in additon to eg4). However, the relay system specifics have not been specified as of this time, that I've seen. Perhaps this is a basic workflow but I'd like to see some exact hardware suggested that would accomplish this workflow.

Whether on or off grid, the hybrid should be able to guard against backend to the grid, no?

When the grid is off, hybrid can frequency shift to control all connected arrays.

But when grid is on, batteries are full, and we don't want any backend to grid...then the hybrid MUST have a way of communicating to microinverters to shut off. It can't be done by frequency shifting while grid is on, so it would have to be done by some relay (regulatory) system. What hardware/component would accomplish this regulating action?

 

[the.shining]

...and because this is a daily load sharing system, sub paneling isn't an option. Worst case scenario I can limit loads or cut off breakers at main panel, but neither I nor the common customer wants to rearrange their circuit breakers into sub panels. I'm trying to design a system that is turn key not only for me but for common scenarios where people value inverter diversification, multiple power paths, seamless load sharing, on and off grid solar power.

 

[400bird]

Enphase provides 25 warranty on their microinverters. Eg4 provides 10 yr warranty. Whether these warranties can be depended on is anyone's guess, but all else being equal, enphase microinverters appear to be the cheaper and longer life inverter at the present time.

And a John Deere costs more than a Ford.
You're comparing two inverters with very different features and functionality, unless you're getting into the Enphase battery. In that case it's more like comparing a kit car to a new car off the lot.

Comparing the value of each company and their ability to back their products, I'd go with Enphase every day of the week. EG4 imports inverters designed and manufactured by another company, they just get custom paint and stickers. Enphase has their own products and engineering. One has a long history with honoring warranty even early on when the failure rate was higher. The other is a new company with nearly daily complaints in this very forum.

That said, all of this is a mile away from where you started this thread.

 

[ksmithaz1]

The thread is about creating a Frankensystem. There is no way I would ever intentionally mix micro inverters with an AIO on a new install. It just sounds dumb, and now you are all worried about weird interactions, why would you want to intentionally create something so complex? I see dubious benefit and the likelihood of strange behavior. Heck throw a couple of windmills in there while your at it. Rube Goldberg would be proud.

 

[ksmithaz1]

The thread is about creating a Frankensystem. There is no way I would ever intentionally mix micro inverters with an AIO on a new install. It just sounds dumb, and now you are all worried about weird interactions, why would you want to intentionally create something so complex? I see dubious benefit and the likelihood of strange behavior. Heck throw a couple of windmills in there while your at it. Rube Goldberg would be proud.

For the cost of the micro inverters you could add extra panels.

 

[zanydroid]

The thread is about creating a Frankensystem. There is no way I would ever intentionally mix micro inverters with an AIO on a new install. It just sounds dumb, and now you are all worried about weird interactions, why would you want to intentionally create something so complex? I see dubious benefit and the likelihood of strange behavior. Heck throw a couple of windmills in there while your at it. Rube Goldberg would be proud.

How else would you use module level optimization though? I use microinverters because I only have roof space on a city lot, and low quality (highly obstructed) at that.

If you need it, the alternative is optimizers. That is no better. You have vendor locked in SolarEdge, then not amazingly documented TIGO, then SolArk which is brand new.

There are somewhat more people experimenting with microinverters on the forum than optimizers. Maybe all the Tigo optimizer people get it to work then disappear.

 

[zanydroid]

And it sounds like the original system I proposed with the microinverters feeding into the main panel (instead of the eg4) could be feasible for ON grid AND OFF grid (using some relay system in additon to eg4). However, the relay system specifics have not been specified as of this time, that I've seen. Perhaps this is a basic workflow but I'd like to see some exact hardware suggested that would accomplish this workflow.

AFAIK EG4 has not released a MID. If you add an Enphase or other MID on top of a hybrid IMO the system is getting too franken for my taste.

 

[k490]

...and because this is a daily load sharing system, sub paneling isn't an option. Worst case scenario I can limit loads or cut off breakers at main panel, but neither I nor the common customer wants to rearrange their circuit breakers into sub panels. I'm trying to design a system that is turn key not only for me but for common scenarios where people value inverter diversification, multiple power paths, seamless load sharing, on and off grid solar power.

Microinverters as far as I know don't have a way to throttle the output to match what you're using in the home. The manufacture intended them to be used with a utility interconnect agreement. The feature you want is only available in a small number of UL listed inverters that I know of like the Sol-Ark, and EG-4 18PVK. It's more than just a relay it actually throttles the output to match what your home is pulling. The CT clamps notice that your home is starting to pull power from the grid, and it adds power to your main panel until those CT clamps show no more power being pulled.

The CT clamps go around the large 2/0 wires coming from the meter to your main disconnect.

You would not be able to control the microinverters by using a manual breaker or relay they would feedback to the grid if you had no interconnect agreement, they would investigate what you're doing. I know some just receive a letter, but I would not be surprised if my utility actually reported to the city have them inspect what you're doing. These days all the have to do is pull up google see panels on an unpermitted house going to result in a fine plus bunch of hoops to jump through. This is why I was advocating for a lower cost permitted microinverter string then you can add your own battery system later. The utility won't be upset about back feeding city won't be after you.

 

[ksmithaz1]

How else would you use module level optimization though? I use microinverters because I only have roof space on a city lot, and low quality (highly obstructed) at that.

If you need it, the alternative is optimizers. That is no better. You have vendor locked in SolarEdge, then not amazingly documented TIGO, then SolArk which is brand new.

There are somewhat more people experimenting with microinverters on the forum than optimizers. Maybe all the Tigo optimizer people get it to work then disappear.

*I* wouldn't mix it in a new build. Opinions are like *ssholes so take it with a grain of salt. I think the benefit of this seriously mixed approach is far outweighed by the complexity and expense. That being said, if I took a micro-inverter approach, I would be all in on that approach, All the way down to the enphase battery setup. I don't think micro-inverters lend themselves well to a cafeteria plan solar setup.

Then again, if I wanted battery storage, I wouldn't run the microinverters at all. I think you can arrange your panels in strings to take advantage of a less expensive AIO, or even a multi-mppt & DC inverter only, without sacrificing any production at all. Anecdotely, I've covered some of my newer panels with cardboard, partially and completely. I saw a corresponding drop in output that was pretty much in line with expectations, I've not seen anyone raving about either optimizers or micro-inverters on how they boosted production, in low light and shading scenario's. Mostly it's I spent a ton of $$ and it seems to help, maybe, which is probably related to the third line above.

I'd put the extra effort and expense in to optimizing my panel placement and strings, maybe get an extra panel or two, if you can figure out where to stuff it. To that end, I've been shuffling and moving around a couple of strings in my back yard. I'm finally gettting around to putting up a couple of block structures to use as storage and to mount my arrays, based on my production findings. If you spend some effort and extend multiple string connections to where the panels are, then maybe shuffle the topology around and optimize it that way, you can probably get a good handle on what works best.

 

[zanydroid]

That being said, if I took a micro-inverter approach, I would be all in on that approach, All the way down to the enphase battery setup.

The problem with using Enphase batteries is that now you’re using an inherently loser design approach for batteries. They parallel together multiple altered IQ8s, which are upgraded grid tie inverters. Sure they’re much better regulated than a regular grid tie inverter for use in off grid, but I don’t think they have good surge. These are also 1st/1.5th generation of that specific microinverter iteration.

I saw a corresponding drop in output that was pretty much in line with expectations, I've not seen anyone raving about either optimizers or micro-inverters on how they boosted production, in low light and shading scenario's. Mostly it's I spent a ton of $$ and it seems to help, maybe, which is probably related to the third line above.

I think of microinverters as the easiest way to set up a fully parallel setup. They have reasonable size output wiring due to 240VAC and reasonable current. Fusing is in the microinverter. They have the advantage of not needing to activate bypass diodes and put heating load on them. So there is now zero risk of hot bypass diodes melting the panel or having to be replaced. It’s more expensive to swap a microinverter but easier/more supported than digging into a potted junction box. I can’t imagine doing that on a roof, but maybe some people are that good.

They also are unbeatable in smaller roof planes. RSD requirements basically invalidate sub arrays smaller than about 5S due to the minimum string size if you want to stay within RSD manufacturer design limits (going below it probably runs into dark start risk etc. probably not a "will spontaneously combust" situation. another issue is that you might have a rough time finding MPPTs/AIOs that combine low start voltage with full code compliance esp for NA-specific things like AFCI)

The big PITA microinverters do to you is having to deal with AC coupling at a system size where DC is theoretically superior (at least in the grand scheme of things). And zero export microinverters have more intrinsically complex dependencies. Namely the control signal needs to get fanned out to all the microinverters and this is not super reliable. On wireless brands, you have to manage wireless signal quality. On PLC brands you have to manage PLC quality. For a good time Google for horror stories of filtering PLC for Enphase installs. Suddenly microinverters are no longer brainless like microinverter install teams expect them to be (and have used as a crutch)

 

[the.shining]

Is the proposed solar system from the Franken family? Hell yes.

Are there more pros than cons? Hell yes.

Some people need to update their pricing cards. Microinverters are cheaper and have 2.5x longer warranties. Yes. It's more complex, but don't try to win the ROI war by arguing against micros.

I get the argument to permit a micro system, then add a hybrid/battery later. That might be the simplest best answer than trying to mess around with Hoymile and open source software.

 

[zanydroid]

Some people need to update their pricing cards. Microinverters are cheaper and have 2.5x longer warranties. Yes. It's more complex, but don't try to win the ROI war by arguing against micros.

Multi-port microinverters are NOT cheaper than the cheapest grid tie Growatts/etc with 1741SB, even with RSD added into the mix (and if it's a ground mount you don't need them). Assuming you can efficiently max out the grid tie inverter.

Grid tie inverters pull further ahead if you can be smart about overpaneling (microinverters are inherently less flexible with this), for instance by using orientation diversity when over-paneling, or if you need to optimize for harvesting across all seasons.

There was a recent thread where we did some math on it and it comes up all the time.

The longer warranty needs to be hedged against the company dying or getting murdered by geopolitics (see: Huawei and other companies subject to trade restrictions or maybe pulling out using trade restrictions as an excuse). As well as the extra labor cost, which I seriously doubt Hoymiles is covering (not that I read their warranty before buying).

Another advantage of micros is that you need to do much less learning and prep work before you're ready to install one.

I get the argument to permit a micro system, then add a hybrid/battery later. That might be the simplest best answer than trying to mess around with Hoymile and open source software.

FWIW when I was talking to ncsolarelectric about the OSS stack (which I'm not using, I have a DTU Pro, 2.4GHz version, that I bought from him along with the rest of the hardware), he said he had one customer that tried to get it to work, and failed.

 

[ksmithaz1]

Is the proposed solar system from the Franken family? Hell yes.

Are there more pros than cons? Hell yes.

Some people need to update their pricing cards. Microinverters are cheaper and have 2.5x longer warranties. Yes. It's more complex, but don't try to win the ROI war by arguing against micros.

I get the argument to permit a micro system, then add a hybrid/battery later. That might be the simplest best answer than trying to mess around with Hoymile and open source software.

I've said before, the best ROI is generally micro-inverters, no batteries, grid tie, minimal number of panels mitigating TOU or expensive power.

Line card: ~$120 per panel for micro-inverters. 12 panels, $1440 you just bought a 6000. Warranties are wonderful as long as you never have to use them. Add a battery to a micro-inverter setup and you can toss your ROI out the window. Thus it depends on your objective. Micro-inverters don't scale as well, simply because you have to keep buying them, and your not getting any inverter capacity along with it.

If you don't grid-tie, micro-inverters are even a worse idea. Your AC output is now directly tied, you end up with another box to do the inverting, and batteries, and you get to lose energy every time you convert it.

I have 47 active panels. That's like $6000 worth of micro-inverters, with a theoretical max output of around 18KW, and zero battery capacity that only works with grid tie and sun. For that you can get a big SolArk or EG4, and tie vanilla batteries to it and actually generate power when the sun doesn't shine.

 

[the.shining]

FWIW when I was talking to ncsolarelectric about the OSS stack (which I'm not using, I have a DTU Pro, 2.4GHz version, that I bought from him along with the rest of the hardware), he said he had one customer that tried to get it to work, and it failed

I'm a software engineer. Nothing stabile about software. I wouldn't be adverse to open Hoymile for my own system but I couldn't install it as a turn key system for 3rd parties. My home's system will be a proof of concept for any potential clients who want the most efficient, flexible, and resilient solar system for the best price. When you factor in warranties (credible)...micros win. Hybrids have 10 yr warranties, which makes them 2.5 less dependable than micros. Yes, we can debate the credibility of warranties, but 25 yr vs 10 yr warranties puts my mind and most customers minds at ease