400 Amp Service and EG4 Grid Boss

[Pilot Bob]

The builder said we will have a 400 Amp service into a new home with two 200 Amp panels. Will this require 2 each of the EG4 Grid Boss and a EG4 Flex Boss 21,or is it feasible that we will be able to run most loads on one of the 200 Amp panels? With 1 Flex Boss is was planning on having 22-23kw solar input, If I need 2, can I divide the solar input between the two so each can manage the loads of the panel? In my county, a ground mount system can only produce 120% of what the house uses to limit energy going to the grid. Hopefully this makes sense.

Thanks, Bob

 

[Quattrohead]

What are your architects calculations for your loads?
Mine grossly over calculated for reasons that I did not understand and I ended up correcting them and getting it down to a single 200 amp panel again.

 

[Pilot Bob]

He has not provided yet, although he did say it was close but thought it best to provide the additional for future.

 

[Dagoth Ur Does Solar]

I don't know what most people have in their homes, but lots of the posts that I see here it looks like builders or electricians are often heavily overestimating these load requirements.

One thing to consider is that if you have enough loads to require 400 amp service, you're probably gonna need a real big solar system.

But really, I'd want to do the calculations myself and double check just to be sure.

 

[wpns]

I would have him put in the 400 amp service if it makes him happy, but only install one 200 amp panel, and put all of your loads on that. Add an Emporia Vue or equivalent, and you will know how close you are to maxing out your system, or if you ever even get close to 200 A. You can always expand later. Have the electrician leave room to put another 200 amp panel in if you really need it, but then you can start with one grid boss and some number of flex boss 21 inverters, and expand later as required.

Note that the FlexBoss 21 is only good for 75 A, so you might need two or three of them depending on how close to your supposed 200 amp load you are. Just leave room in the installation location for extra inverters (and batteries) and you’ll be fine.

You could even put in the second 200A panel for now, and call it non-critical (grid-only) loads, to reduce the required size of your solar system.

 

[etekberg]

No one here can answer what loads you have, but reasonable chance you don't need it. I have a 400 amp service but my peak 15 minute power usage from the electric company data for last year was 12kW before I added a 12kW car charger. Now it is 18kW over the last year, but I don't charge often. I would guess most 400 amp services are for the purpose of additional circuit breaker room rather than load.

I'm in the process of converting one of my 200 amp panels into a grid only loads panel, and the other into a backed up loads panel to be powered the inverter.

 

[kscessnadriver]

You guys understand it’s very easy to do the load calculation as required by the NEC. There’s multiple places online that the form is automated, you just put in what the house has

 

[CyberBill]

Pilot Bob - Did you ever make progress on this build or discover anything for a 400A service?

Right now I'm using two separate 200A services (with two meters) coming into my property, one to the house and the other for the shop, and I am looking to combine them behind a single 400A meter. During the day I make a ton of solar, which gets exported at $0.03/kWh, some of which comes right back into my shop where I pay for it at $0.10/kWh!

My plan is to bring 400A service into a main panel, which gives 200A to the house, 200A to the shop, and 200A to a new set of buildings. It would be really nice if I could install one set of batteries to power the whole setup!

 

[peufeu]

I have 25A service

Besides that make sure you check the amp rating on the passthrough relay in the inverter, the one between grid port and backup output...

 

[Tommytwotone]

Pilot Bob - Did you ever make progress on this build or discover anything for a 400A service?

Right now I'm using two separate 200A services (with two meters) coming into my property, one to the house and the other for the shop, and I am looking to combine them behind a single 400A meter. During the day I make a ton of solar, which gets exported at $0.03/kWh, some of which comes right back into my shop where I pay for it at $0.10/kWh!

My plan is to bring 400A service into a main panel, which gives 200A to the house, 200A to the shop, and 200A to a new set of buildings. It would be really nice if I could install one set of batteries to power the whole setup!

You may find that pending your POCO it is actually (2) 200 amp panels fed from the meter or that this is the more cost effective way to do it. The 400 amp residential panels are very pricey as I recall and our POCO does not support that method.

As I understand it the Gridboss is one per install deal at the moment although I know of a group that asked about doing more than one and who knows that may happen.

We have two 200 amp panels with a Gridboss tied to one of them. Obviously when we are feeding back toward the grid any excess power consumed by the other 200 amp panel, that includes a barn feed in our instance as well, would be before the meter so it would just get used and not cross the meter if there was a load.

That does not address one battery bank for bigger services. Is it possible to feed 400amp to 600 amp services with one bank? I gather it is as some entire factories are 100% solar with generator backup NO grid. At this point I do not believe the Gridboss supports that size application but multiple Flexboss units, 18k units etc etc fed into a combiner panel may be the way to go.

 

[mciholas]

He has not provided yet, although he did say it was close but thought it best to provide the additional for future.

Beware of this thinking. Architects over specify everything to the detriment of the budget. For my 35,000 SF office building, the architect specified 90 tons of cooling, and I cut it back to 42 tons and those units have never needed even stage 2 activation after 10 years. I could have gotten by with 25 tons.

200 amps is 48 KW. Unless you have some really wild loads, it is extremely unlikely you will pull anywhere near that load. If you do have issues with tripping the main breaker (something I have NEVER seen under non fault conditions), then relatively minor lock outs on simultaneous loads can solve this problem.

Also, realize the architect is basing their calcs on very old rules of thumb when we had 100 watt incandescent bulbs and not LEDs, when appliances weren't energy star, when computers used 300 watts, when TVs used 250 watts, etc. Houses use a lot less "incidental" energy than they used to, including better HAVC stuff, too.

Also, in the end, you can have two 200 amp panels, just put everything you DON'T want backed up in panel #1 and everything else you DO want backed up in panel #2, and put the GB ahead of panel #2. For example, the pool pump and heater goes in panel #1 since you can live without that in a grid down situation. Indeed, it is helpful to split the loads like this so grid down automatically load sheds and your battery last longer. As long as you have permission to back feed the grid, then your panel #1 will use your power you back feed. You can even move the CTs to the combined flow to both panels and set the system up for zero export.

Mike C.

 

[EG4TechSolutionsTeam]

Here are some wiring diagrams that might help with the 400Amp Service. In case anyone needs them.

https://eg4electronics.com/wp-content/uploads/2024/12/Dual-GridBOSSes-on-400-A-Residential-Service.pdf

 

[FilterGuy]

Will this require 2 each of the EG4 Grid Boss and a EG4 Flex

If you want whole home backup, yes.

However, if all of your critical loads are on one of the 200A panels, you could just but the inverter and gridboss on that side.

 

[niktak11]

Here are some wiring diagrams that might help with the 400Amp Service. In case anyone needs them.

https://eg4electronics.com/wp-content/uploads/2024/12/Dual-GridBOSSes-on-400-A-Residential-Service.pdf

Are there any plans for a 400A Gridboss (or 200A Gridboss that can be used in parallel with a common inverter system)?

 

[Chuck2]

Looking at the manual for the Gridboss, is everyone sure that it will not output 350A continuous if you utilize the Backed up and Non Backed up ports simultaneously for the two 200A panels? You have 3, 90A inverter breakers capable of feeding power into the gridboss as well as one 200A grid breaker (should you choose to install it). If you used inverters rated for 50A continuous and they are all backfeeding the Gridboss on the inverter ports while the grid is supplying up to 200A on the main grid input breaker, what is to stop the unit from actually delivering 350A continuous and at least 500A surge if the grid stayed at 200A (which it WILL exceed for surge) in addition to around 100A each from the inverters in a surge?

Has anyone actually tested what the Gridboss will deliver? The busbars in the EG4 wall mount batteries are rated for 600A, so unless they really cheesed out the internals on the Gridboss comparitively, as long as the loads are spread between the smart ports, the "backed up" and the "non backed up" ports, the unit should deliver way more than 200A continuous and over 500A surge and be perfectly safe. Should handle a 400A service pretty well on it's own really.

The only way to actually STOP it from sending out 350A continuous would be if they purposefully limit the inverter outputs dramatically as the incoming CT's from the grid + the incoming current from the inverters exceeded 200A in the software. Are they actually doing this, or are we all sizing systems around the idea that the Gridboss is only doing 200A, when in reality it is 150A worth of inverter PLUS 200A worth of grid? I mean, there is 270A worth of overcurrent protection just on the inverter inputs alone..... neverminding the 200A grid input breaker..... The overcurrent protection in the INPUTS to the Gridboss are 470A alone, if you run 3 18Kpv or 2 Flexboss21 units with a 200A grid breaker for instance.

Why is the Gridboss not PARALLELING the 150A worth of continuous inverter with the 200A worth of grid? Or is it....... and we're just not talking about it?

 

[Chuck2]

I happened across a "Tech Specs" section for the Gridboss on the bigbattery website and in there, there is a specification listed for "Internal Busbar Rating: 350A". This would appear to support my assertion that the unit might actually be capable of 350A continuous, not 200.

That's a big, big difference to someone that may be interested in the topic of this thread, potentially running a 400A residential service with a Gridboss.

As stated, unless the software aggressively drops the inverter output voltages as the total system meets and exceeds 200A, there is nothing to stop that system from making use of all the available input power circuits together. This is precisely why, when you use one of these inverters to backfeed an existing panel, the breaker must be sized in conjunction with any other possible input sources (like the panel main breaker), such that the total continuous over-current protection available to that panel does not exceed 120% of the panel rating.

I think in the case of the Gridboss, they are counting on the inverter sources self-limiting to 50A continuous, leaving the continuous input current at 350A max with 3, 50A inverters plus 200A grid, even though the over-current protection available is actually 470A with 3, 90A inverter breakers plus 200A Grid breaker, if configured for 3 Flexboss21 units, for instance.

Can anyone with a Gridboss installed just throw some load on it and see what happens when the load blows right past 200A? I suspect nothing happens, as long as the available inverter power is not exceeded.... right up past 250 and 300+ Amps. But that is the question. Are they using software to turn down the inverters or not?

 

[Quattrohead]

It has CT's on all of the inputs and outputs and will software limit itself to 200 amps. This has already been talked about when the previous firmware was a bit oversensitive and it was shutting down on brief surges when it didn't need to.

 

[Chuck2]

Well shoot. I wonder why they feel the need to limit it that much if the busbars are good for 350A and it has so many outputs available to spread the load between. I was really hoping to use one of these. In fact, it would be nice if there were one with busbars at 400+ amps and just be done with the problem and skip all the voodoo trying to support a 400A service. Buying 2 Gridbosses does not solve that problem..... that halves up your inverter power and they cannot talk to one another on opposite Gridbosses or push power back and forth to help one another out. I wouldn't be surprised if the most common service pulled for a residence was 400A at present.

Can you link to the discussion mentioned where this was already talked about? Would like to read it.

Thanks.

 

[Chuck2]

I think I found the GB discussion mentioned:

Gridboss early firmware sensitivity.


I am currently wondering if buying a 400A panel and just combining 2 of my 200A services to it as inputs and then backfeeding it with some flexboss21 units would be a more reliable solution than the Gridboss. ZERO percent chance of it caring about any sub 400A transient loads moving through it and would still allow a person to do a full 400A while sharing the load with as many inverters as you like.

 

[CyberBill]

Here are some wiring diagrams that might help with the 400Amp Service. In case anyone needs them.

https://eg4electronics.com/wp-content/uploads/2024/12/Dual-GridBOSSes-on-400-A-Residential-Service.pdf

This is SUPER HELPFUL! I was really curious how I could backup my whole property with one set of batteries, and I hadn't even considered that one bank of batteries could be shared by multiple inverters which were then backing up each 200A panel. That's very clever, and I think it gives me a complete solution.

 

[Kazoo]

Here are some wiring diagrams that might help with the 400Amp Service. In case anyone needs them.

https://eg4electronics.com/wp-content/uploads/2024/12/Dual-GridBOSSes-on-400-A-Residential-Service.pdf

Thank you for sharing this! In this case with a common battery bank, how should communication be set up. Two banks of batteries each talking to its own gridBoss's main inverter, but still connected with bus bars? All batteries talking to one main inverter, with the other Gridboss's inverter just using voltage (no battery communication)?

 

[EG4TechSolutionsTeam]

Thank you for sharing this! In this case with a common battery bank, how should communication be set up. Two banks of batteries each talking to its own gridBoss's main inverter, but still connected with bus bars? All batteries talking to one main inverter, with the other Gridboss's inverter just using voltage (no battery communication)?

You would connect all the batteries in parallel and have the master battery communicating with the master inverter.



The recommended wiring would be to have all the battery banks connected to external bus bars and have connections going to each inverter and you would have battery share enabled.

 

[Kazoo]

You would connect all the batteries in parallel and have the master battery communicating with the master inverter...

Thank you for the reply. Sorry for not specifying but my question is regarding your dual-GridBOSS setup. If there are 2 GridBOSSes, 6 FlexBOSSes, and lets say 8 batteries for the sake of argument; all batteries are wired to a common bus bar, so both GridBOSS systems share the same bank - how does closed loop battery communication work? If I understand correctly the GridBOSS systems don't communicate with each other, so which inverters are able to talk to which batteries? Thank you

 

[rahine]

Following:
Great question as I didn't think about that part in my design. I am designing a system with 2 Gridbosses each paired with 2 Flexxbosses for my 400a service (2- 200amp panels) and have all 4 inverters sharing one large battery bank 8 wallmounts or 4 racks.

 

[Chuck2]

My case is similar and I think I have decided to run multiple 18kpv units instead as I cannot see any practical benefit to the Gridboss system in my case. I would still have to install a blade style disconnect as the POCO could care less about the breaker style disconnect in the Gridboss. I will have to swap out all 3 of my 200A breaker style disconnects at my service entrance now, and the same is true if I used the Gridboss. If I were to use multiple inverters per each 200A service, then a gridboss could take the place of a combiner panel for paralleling the units, although a $200 panel vs a $2500+ Gridboss again seems pointless.

The only feature I like is the ability to use the built in bypass transfer for inverter maintenance. If you can mount the unit close enough to any homeruns, then you can utilize the smart ports and that would be another benefit I cannot use. My service entrance is 200 feet from the nearest main panel for the home. I have no plans to have the inverters or batteries or solar inputs any closer than that to the home anyway, so the smart ports are useless. For the inverter bypass I will install a manual transfer switch to each inverter (still half the cost of a Gridboss) and then repurpose my existing 200A breaker style disconnects to interrupt the feed to the "Load" side of the 18kpv should I need to flip the transfer switch and bypass an inverter for some reason.

I'm thinking one 18kpv per 200A service, one blade style disconnect outdoors in place of the original breaker style disconnects and in the event of a grid outage, have a few select smart breakers over in the home main panel drop out the dryer or ovens or one water heater, so on and so forth as needed, should the usage stack up by others in the house to avoid the need for paralleling inverters to handle worst case peak events WHILE the grid is down and unable to provide that short-term peak loading.