EG4 18K/Sol-Ark 15K with 600A Service

[babgvant]

We are building a house that will have 600A service. I would like to install a system capable of providing whole home backup, and potentially run "off-grid" if we want to.

After some research, it appeared that stacking 3-4 EG4 18K / Sol-Ark 15K would check the boxes. With 200A pass-through, we'd need at least 3, a fourth would provide 200A of inverter capacity during "off-grid" moments.

At a high level, I was expecting the topology to look something like this.



But, after reaching out to EG4 and Sol-Ark, I am no longer confident that we can stack the inverters in this way.

Is this possible? If not, what other options are there?

Thanks

 

[zanydroid]

I don’t see why not. All AC in and AC out are overcurrent protected to 200A. You do have 200+150A of available fault current within a single inverter if shit hits the fan (grid plus 3 other inverters), but I would think this is vetted as part of certifying the stacking.

What specifically did they tell you? Hard to react against/criticize it , understand the dissonance, with no details

 

[DIYrich]

Seems like the only thing not in parallel is the batteries. You should put them in parallel. You might want to consider the growatt sph 10000tl-hu-us and parallel more.

 

[HighTechLab]

I don't see a problem here either...the battery bank is the absolute smallest you can make it to support 4x inverters, so you may consider adding more of that if you ever want to come close to meeting the demand of the home with solar / without grid.

You will need an interlock in the "AC combiner" to ensure that you can't have the feed directly from the grid bypass on at the same time that the AC output of the inverter is on.

600A service is wild and sounds like it might be overkill. Is your house completely electric appliances?

 

[Brucey]

Say you have three 200A panels. Each of those is capable of 48kW. So total possible max of 144kW.

Each eg4 18kpv has a battery inverter capacity of 12kW. So even with four of them you'd have enough for full backup of just one 200A panel.

 

[babgvant]

I don't see a problem here either...the battery bank is the absolute smallest you can make it to support 4x inverters, so you may consider adding more of that if you ever want to come close to meeting the demand of the home with solar / without grid.

You will need an interlock in the "AC combiner" to ensure that you can't have the feed directly from the grid bypass on at the same time that the AC output of the inverter is on.

600A service is wild and sounds like it might be overkill. Is your house completely electric appliances?

Thanks. I would love to throw a 6th battery in the mix, but I was told that NEC code only allows me to do 80kWh in the garage.

The switchable bypass will be a manual 600A double throw. When GRID is connected to the inverter combiner it will be physically disconnected from the output combiner panel. Would that be sufficient?

Yes, all electric house with an ADU above the detached garage. I would have preferred to see a lower number on the calcs .

 

[babgvant]

Seems like the only thing not in parallel is the batteries. You should put them in parallel. You might want to consider the growatt sph 10000tl-hu-us and parallel more.

Sorry, I was lazy. They actually are in parallel; we will be using the paralleling kits that come with the PowerPro batteries.

 

[babgvant]

I don’t see why not. All AC in and AC out are overcurrent protected to 200A. You do have 200+150A of available fault current within a single inverter if shit hits the fan (grid plus 3 other inverters), but I would think this is vetted as part of certifying the stacking.

What specifically did they tell you? Hard to react against/criticize it , understand the dissonance, with no details

Sol-Ark never responded.

EG4 provided a wiring diagram that only runs 200A of a 400A service through the inverters (below). Indicated that's all they have, and would not answer any questions around whether it was possible to do what I want to do.



My guess is that this topology is intended to reduce installation cost, and not due to functional limitations within the products.

 

[zanydroid]

EG4 provided a wiring diagram that only runs 200A of a 400A service through the inverters (below). Indicated that's all they have, and would not answer any questions around whether it was possible to do what I want to do.

They don’t provide custom SLDs; you can hire folks to do that though.

Thanks. I would love to throw a 6th battery in the mix, but I was told that NEC code only allows me to do 80kWh in the garage.

It is residential code that governs the limit.

You can work around this by having more batteries back to back on the opposite side of the wall. For instance, a bunch on the wall in an exterior wall of the garage, and then more on the other side on the outside.

Yes, all electric house with an ADU above the detached garage. I would have preferred to see a lower number on the calcs .

Do you have EV charging involved? You can use EVSE load management to chop down the calculations from EVs. You can use general load management to chop other non essentials. You can swap away from high power stuff like tankless electric and resistive dryers to heat pump water heaters and heatpump dryers. Tankless electric to HPWH will be a gargantuan load calculation saving

BTW hightechlab is the owner of a solar retailer with a good reputation on here. Carries EG4.

 

[babgvant]

They don’t provide custom SLDs; you can hire folks to do that though.

Totally understand that from a cost/liability perspective why they won't tell me how to do something. But I asked if it was possible, that's all they would provide.

It has been a struggle to find someone who is willing to do the work. All of the installers I've engaged with want to use systems that aren't going to do what we want, or will only work in a highly compromised way.

It is residential code that governs the limit.

You can work around this by having more batteries back to back on the opposite side of the wall. For instance, a bunch on the wall in an exterior wall of the garage, and then more on the other side on the outside.

Installing batteries outside is possible, but I would prefer not to do that. That wall is going to be very cramped and it gets cold here.

Do you have EV charging involved? You can use EVSE load management to chop down the calculations from EVs. You can use general load management to chop other non essentials. You can swap away from high power stuff like tankless electric and resistive dryers to heat pump water heaters and heatpump dryers. Tankless electric to HPWH will be a gargantuan load calculation saving

We have all the heat pumps. We could probably do without resistive backup heat, but that wouldn't be ideal. There are EVSE in the mix, but even if we drop them out the calc is over 400A.

BTW hightechlab is the owner of a solar retailer with a good reputation on here. Carries EG4.

 

[zanydroid]

It has been a struggle to find someone who is willing to do the work. All of the installers I've engaged with want to use systems that aren't going to do what we want, or will only work in a highly compromised way.

Might need to go up to higher end installers (and with bigger markup)

Are there installers willing to install to a design/plans set you get elsewhere? I dunno, maybe with EE stamps to take more heat off them

 

[zanydroid]

Can you use propane backup heat to knock down the calculations? If you are true off grid you would need propane supply anyway for generator

It sounds like this is an on grid house so it would be more cost effective to use resistive backup.

Installing batteries outside is possible, but I would prefer not to do that. That wall is going to be very cramped and it gets cold here.

You are also allowed by residential code to put the batteries in living space but there are a lot of restrictions. I suspect in a lot of cases it would look weird in the adjacent room. Maybe you can have architect design the layout to optimize for it. I’m not super familiar with the max in living space but it is probably 40kWh

Also would be good to confirm what revision of residential code you are on.

Can you get the habitation certificate or whatever for the off grid build, based on a full size generator alone? Assuming you are forced to have one anyway. Then slowly add the solar from scratch (EDIT: never mind, you are on grid. That should make it strictly easier to do incremental build of solar)

Or get some of the heavy lifting installed for you, like the solar array, and then you sort out the rest of the system.

 

[babgvant]

Can you use propane backup heat to knock down the calculations? If you are true off grid you would need propane supply anyway for generator

It sounds like this is an on grid house so it would be more cost effective to use resistive backup.

Sorry, should have clarified. This is not an off-grid system. Just a system that I want to be off-grid capable. We should be completely fine with 3x 15K/18K (150A) the load calcs are a worst case. Given the design of the house, even in the worst conditions, it's unlikely that we'd need the resistive backup. It's one of those things that even if we pulled it and the EVSE out, we'd be on the line for 400A.

Since it's a totally new build, I think it makes sense to roll with 600A even if we could cut things out to make 400A work because it is so close.

You are also allowed by residential code to put the batteries in living space but there are a lot of restrictions. I suspect in a lot of cases it would look weird in the adjacent room. Maybe you can have architect design the layout to optimize for it. I’m not super familiar with the max in living space but it is probably 40kWh

Max indoor is 40kWh in this location. 80kWh is possible in a garage or outdoor. It's possible to do more, but that opens a can of worms around permits and fire code. It is a fight we could fight, but given that we're unlikely to need more than 80, it probably wouldn't be worth it.

The limits are bonkers. It's totally fine for me to park a 200kWh Hummer in the garage with a more dangerous battery chemistry, but installing 90kWh of LFP would require commercial fire suppression systems .

Also would be good to confirm what revision of residential code you are on.

2020

Can you get the habitation certificate or whatever for the off grid build, based on a full size generator alone? Assuming you are forced to have one anyway. Then slowly add the solar from scratch (EDIT: never mind, you are on grid. That should make it strictly easier to do incremental build of solar)

Or get some of the heavy lifting installed for you, like the solar array, and then you sort out the rest of the system.

I'm not legally allowed to do any of the work myself. Even if I could get away with it, my wife would not let me get away with it :D.

 

[zanydroid]

Since it's a totally new build, I think it makes sense to roll with 600A even if we could cut things out to make 400A work because it is so close.

Yes I wrote 80% of that when I thought it was an off-grid build. Since it's on-grid, there's less value to aggressively dieting the load calculation. Unless 400A->600A service drop is a big jump up in monthly fees.

2020

OK, cool, just wanted to make sure you weren't unnecessarily getting pulled into the 80kWh / 9540 requirements.

I'm not legally allowed to do any of the work myself. Even if I could get away with it, my wife would not let me get away with it :D.

Ouch. Well, you need to get smart at hiring then (here we are allowed to do everything solar/ESS related ourselves). Maybe if it's a big enough project, you can bring someone in from out of area.

 

[HighTechLab]

This is the gist of the way I would set it up.

600A hardware is REALLY expensive and almost exclusively three-phase. To see what I mean, attempt to track down a 600A on-off-on manual transfer switch... I'm seeing $7,000 to $11,000! 600A main-lug only panelboards are about $4000 each... and the electricians to install them will most certainly bid it like an industrial job.

For reference, to carry 600A of current, you absolutely will be doing parallel runs. Something along the lines of 3x 3/0 or 2x 400MCM, options depend on how many lug openings the breaker has. This is my point, the hardware to handle this kind of current is extremely spendy because it's not even close to residential grade.

I think this system easily hits over $100k parts/labor very quickly. There are many ways to shave this, and the best place to start is fitting your loads on a 400A service. I just did a design on an all-electric house that had two tesla chargers and easily fit everything on a 400A service. We only backed up 200A on that one, because things like the clothes dryer and EV chargers were easy to load-shed when the grid goes down and we put a 50A welder outlet in the garage from the critical loads panel so that a mobile charger could be used in the event of a prolonged outage.

 

[Quattrohead]

Yeah the power load calculations on new homes is ridiculous, they don't consider modern energy efficient appliances at all. My original quote was for 250 amps total load. With a few small changes and a little education for the designer, I got that to well below 200 amps.
ICF walls with spray foam insulation on the roof deck, first HVAC calc was for 5 tons which I knew was totally wrong, made them recalculate it properly and it came to 2.5 tons, right where I thought it should be.
And this is for an all-electric house in central florida, 2500 ft.

 

[Quattrohead]

Has Dexter has implied, try and get yourself down to at least 400 amps.
Maybe even split the main home and other living area into two entirely separate feeds and get them down to 200 amps.

 

[babgvant]

I think this system easily hits over $100k parts/labor very quickly. There are many ways to shave this, and the best place to start is fitting your loads on a 400A service. I just did a design on an all-electric house that had two tesla chargers and easily fit everything on a 400A service. We only backed up 200A on that one, because things like the clothes dryer and EV chargers were easy to load-shed when the grid goes down and we put a 50A welder outlet in the garage from the critical loads panel so that a mobile charger could be used in the event of a prolonged outage.

Thanks. I'm painfully aware of the difference in cost .

Unfortunately, this is a conversation we have already had. A big part of it is that with an ADU items like the stove/oven, HVAC, and water heater are doubled up.

 

[HighTechLab]

Thanks. I'm painfully aware of the difference in cost .

Unfortunately, this is a conversation we have already had. A big part of it is that with an ADU items like the stove/oven, HVAC, and water heater are doubled up.

I think then my drawing stands as how I would try and tackle this as one system...

The only other option I could think of is to make it two systems, one with a single inverter handles the (presumably) 200A for the ADU and then a 3 inverter setup on the 400A system for the main house. Perhaps this helps with your 80kWh battery bank limit?

 

[green-river]

I’ve been working on calcs for a similar 3-structure property with ADU with a friend locally here. It is a challenge because all the electric appliances are doubled up with essentially two homes on the property. A few things I’ve found to help bring down the amps:

Cooking: there are new appliances coming on the market that have a battery in the oven so it can run on 120V, instead of a 50A 240V circuit, like the Impulse or the Copper.

- https://www.impulselabs.com
- https://copperhome.com

Water heating: Rheem and A.O. Smith both make a heat pump water heater (HPWH) now that runs on 120V instead of a 30A 240V circuit. Additionally Rheem has an option for a 15A 240V heat pump water heater that has a bit more first hour capacity.

When kept at 140°, and using a mixer valve, they all provide a lot of capacity.

 

[babgvant]

I’ve been working on calcs for a similar 3-structure property with ADU with a friend locally here. It is a challenge because all the electric appliances are doubled up with essentially two homes on the property. A few things I’ve found to help bring down the amps:

Cooking: there are new appliances coming on the market that have a battery in the oven so it can run on 120V, instead of a 50A 240V circuit, like the Impulse or the Copper.

We looked at doing that, but the upfront cost and future lock-in of these types of device made it a hard thing to opt for. Lock-in was a bigger part than the up-front cost. When the induction range in the ADU breaks, I can run to the big box and get another one from the wide selection of 40A induction ranges. If the range with a battery breaks, my options are extremely limited and expensive.

Water heating: Rheem and A.O. Smith both make a heat pump water heater (HPWH) now that runs on 120V instead of a 30A 240V circuit. Additionally Rheem has an option for a 15A 240V heat pump water heater that has a bit more first hour capacity.


When kept at 140°, and using a mixer valve, they all provide a lot of capacity.

120V ASHP water heaters are a great option in warmer climates. Last I checked they don't sell them here (NE IL). Might be able to get one shipped, but if it didn't work. Would be an expensive mistake .

The house is fairly large, the architect was originally planning to put in two water heaters. We opted to go for one 240V + the on-demand booster. Cheaper and cut the load calc down. Just another part of the load calc math problem. The on-demand booster should only get used in worst case situations, when the house is full of guests.

 

[green-river]

It is eye-opening how much more capacity you get out of a tank though when you raise the temp to 130º, 135º, or 140º. I've had 8 guests over for the weekend and a 50-gallon HPWH, set at 140º, covered all showers all weekend without a problem.

In northern Illinois, the groundwater temps are not great which might make a 120v HPWH not ideal. I think they're conservative on selling them in the northern half of the country because there is no way a 120v element can keep up. A 240v HPWH running in hybrid mode would likely still fit the needs. Maybe get the bigger 80-gallon. You'd likely run in heat pump mode 90% of the time, and just use the two resistive elements for backup for high use.

I'm not sure load calcs can take into account an appliance that 90% of the time uses 2 amps, and only a few hours a year uses 30 amps. As hybrids become more mainstream perhaps calcs could evolve.

 

[green-river]

We looked at doing that, but the upfront cost and future lock-in of these types of device made it a hard thing to opt for. Lock-in was a bigger part than the up-front cost. When the induction range in the ADU breaks, I can run to the big box and get another one from the wide selection of 40A induction ranges. If the range with a battery breaks, my options are extremely limited and expensive.

Fair point about the lock-in. If these early models work out and become more common, we're still probably 5-10 years away from battery stoves being at big box stores. I'm in a rural area so definitely understand the expense of mistakes finding/shipping appliances from farther away.

For the lock-in though, you can, and likely should, run bigger wire, so you're future-proofing each location. Especially on a new build. Run 8 AWG wire, even if only using it for a 120v 20amp circuit. So you could still replace it with any common big box model in the future.

For example, I ran 10 AWG to the laundry room even though I only have a 120v heat pump dryer that uses about 8 amps. Because we're starting to see 240v heat pump clothes dryers like from LG. So I want that location to be ready for these new models, or the option to go back to an electric 30A tumble dryer.

 

[GuyG]

600A hardware is REALLY expensive and almost exclusively three-phase.

If he can get three-phase power, that’s probably a good idea. He could save a bit of cash by using two SolArk 30K units instead of four 15 Ks.

But for single phase, I recently found an Eaton 4242L600 for about $1,300. It’s a Loadcenter and not a true Panelboard, but serves my purposes. Also got lucky and found an Eaton 600A fused disconnect, still in box, for $600. If you take the time to prowl around, you can find some high-amp equipment for less than the obscene prices that are the norm these days.

ps, that drawing that eg4 sent you looks crazy complicated/expensive and unnecessarily so. HighTechLab provided a much better one.

 

[Brucey]

The larger solarks >15 use HV batteries I believe. But prob not a budget concern.