FlexBoss21 / GridBoss Issue List

[obsoletion]

Background and setup:

I have a gridboss and 3 flexboss, 32k solar, and 25kw Generac generator. Before I put in the EG4 system, the generator served as my whole home backup with a generac transfer switch. Now the transfer switch is gone and the generator is connector to the generator port on the gridboss. My plan is the generator will only be needed if the grid is down and the solar hasn't kept the batteries up to meet my usage - the Gridboss would start the generator and charge my batteries, then shut it back down.

Here is a issue I am having.

In the gridboss manual, it states it can be set to exercise the generator, but apparently it can't IF it is on grid power. Which doesn,t make sense for an install like mine. I may go 6 months without a grid failure then will go down for a week due to weather. There is a relay in the gridboss that keeps the generator disconnected when the grid is on, so i am not sure why this is an issue.

here are the excerpts from the manual:

 

[mciholas]

I think EG4 may be wording things in a confusing way. You can't USE a generator when the grid is up. Or more precisely, you can't USE a generator while the GB is also USING the grid. Those two relays in the upper right can't be on at the same time, only one can be on.

Bit I am not sure this means you can't START the generator and let it idle under no load for the weekly exercise. That should be harmless. None of the energy it makes will be used, but that's not the point of the exercise procedure.

Also, doesn't Generac have an exerciser feature built into the unit itself? Do you need GB to do that for you?

This could be solved rather trivially with a timer that starts the generator and runs it outside the control of the GB (thus at no load). All that would be needed is a timer that closes the start wires for some minutes every week. The GB should not connect to it since it didn't start it.

Mike C.

 

[obsoletion]

I agree on all points. Here is the weird thing… the pre-computer controller only runs its self exercise when using standard (194/23) transfer switch and not 2-wire start. So when I changed it to 2-wire start for the grid boss it non longer self exercises. I knew this going in but saw in the grid boss manual that is has exercise controls so I figured that would be handled. The grid boss should be able to do this with a firmware change but I don’t have any control over that.

I am thinking of just putting in a relay and resolving this by not relying on the grid boss for exercise.

All that said, it needs better documentation

 

[mciholas]

Make a request to EG4 that they add code to do this properly.

Worst case, you get nothing from them.

Best case, they provide the feature you need.

I read through the EG4 GB docs and couldn't find the exercise feature, even when operating off grid. There are only two places the word "exercise" is mentioned:

---

The generator can also be configured with warm-up, cool-down, and exercise time."

Generator Remote Auto Turn off time(m): [5 – 20]

Sets generator auto turn off time in minutes. GridBOSS will automatically turn power off the generator according to the Auto Turn off Time. This setting can also be used for a generator exercise function.

---

The manual doesn't really explain how to use it as a periodic exercise feature. Things like exercise interval, time of day, etc, are not mentioned.

This is typical of EG4 manuals, they somehow can't be precise when they describe things. They would save maybe 75% of their support calls if they could find someone to write a proper manual. But alas, they don't.

Mike C.

 

[skimandan]

I had a conversation with one of EG4's lead techs regarding the issues in post #1. I wish my tone was more positive, but there were no resolutions.

1. He attempted to lower my PV starting voltage to 120V and received the same error code I encountered. My PV string with 4 panels is still not functioning properly, even though I have no evidence it is not within their documented specs.
2. He requested additional information regarding time of use rates and functions. My opinion is that EG4 is not familiar with the implementation of Time of Use on the West Coast and therefore has not designed a useful tool for it, nor trained their techs, but the feature is listed in their manual. I created a detail needs document for them. If they developed a weekend mode or 7 day scheduling I can use a number of software workarounds to make it work.
3. He confirmed the AC Generator warning is to be corrected in an upcoming firmware.
4. He walked me through an undocumented configuration setting with my Indoor Wallmount batteries (set to brand 1 in the inverter instead of 0 EG4).
5. He stated they know about their documentation issues. I am doubtful it will improve until they revamp the naming conventions in the firmware, otherwise they are documenting embarrassing workarounds.

I really don't want to manage this, but I do want the products they sold me to function as advertised. It is disappointing because I think the hardware is pretty good.

 

[mciholas]

1. He attempted to lower my PV starting voltage to 120V and received the same error code I encountered. My PV string with 4 panels is still not functioning properly, even though I have no evidence it is not within their documented specs.

It is documented in the user manual. But you already knew that, so this has become willful blindness now to that point.

You need 140 volts to start an MPPT, it can track down to 120 volts, but the power will be very weak. You need 250 volts to reach nominal power.



Your 4 panel string isn't going to work. That's the way it is.

Hopefully you can redirect your emotional energy on this issue somewhere positive.

Mike C.

 

[Brucey]

I had a conversation with one of EG4's lead techs regarding the issues in post #1. I wish my tone was more positive, but there were no resolutions.

1. He attempted to lower my PV starting voltage to 120V and received the same error code I encountered. My PV string with 4 panels is still not functioning properly, even though I have no evidence it is not within their documented specs.

They updated their spec sheet to remove it but they used to have a full power mppt voltage range listed of 230V-500V along with the minimum. Boggles the mind why they would hide it now.

 

[Quattrohead]

My PV string with 4 panels is still not functioning properly, even though I have no evidence it is not within their documented specs.

I can't find the details of your 4 PV panel string, can you tell us which panels they are and if you have any RSD/optimizers attached to this string.

 

[EG4TechSolutionsTeam]

1. Many of the settings in the software do not do what you would expect. In order to keep my battery throughout the night I have to Activate A/C charge, then give a time period, then trickle charge the battery for the time period.

We will be reviewing this and posting settings that fit your needs.

2. FlexBoss21 Optimal string voltage is claimed to be 120V-440, but does not appear to work even when string voltage is higher than 140V. This is costing me production I was planning on. https://diysolarforum.com/threads/flexboss21-error.98378/

Operation voltage is between 120-440VDC. However, nominal voltage is at 360VDC.



3. GridBoss may not be able to handle high pass through current from the Grid. Awaiting resolution. Resolved in beta firmware provided to SlowRoller 2/2/2025. https://diysolarforum.com/threads/gridboss-with-flexboss-not-handling-21kw-pass-through.97560/

This will be addressed on our next firmware update.

4. Pressing RSD button on FlexBoss21 shuts down GridBoss backup load even though the grid connection remains active. Not user configurable. 2/5/25 EG4 Tech confirmed this is intended.

When in parallel with the FlexBoss, the GridBoss will go into rapid shutdown as soon as it is initiated.


5. GridBoss Smart Ports - Signature Solar Tech warned me the Smart Ports may not work in a grid down scenario when I was asking how to set it up with my EV charger.

Smart Ports will work in a grid down scenario.

6. Time of Use settings described on page 45 of the FlexBoss21 settings do not exist in the inverter settings. Requires workarounds to enact and the techs were unable to create enough workarounds to meet my 3 pricing periods. Also unable to handle weekend pricing. https://diysolarforum.com/threads/flexboss-21-time-of-use-settings.98597/

TOU settings are for peak shaving, forced discharge, AC charging, and battery priority times. These are only configurable for TOU with 3 time slots available. We will be investigating whether adding a time and date time of use option will benefit our customers.


7. Web monitor does not provide picture of Flexboss21 when linked to Gridboss – its just a nebulous square.

We will be investigating this.

8. Copper only - this was well documented but nobody uses copper at 200A!

We currently have an application to have the GridBOSS certified for use with aluminum wiring.


9. To lower my PV starting voltage to 120V and received the same error code I encountered.

We will be investigating why this error code occurred.


10. He walked me through an undocumented configuration setting with my Indoor Wallmount batteries (set to brand 1 in the inverter instead of 0 EG4).

This chart is beneficial for the correct lithium brand and battery for our products.





Thank you again for your feedback as we work to make our documentation and products better for all users!

 

[mciholas]

When in parallel with the FlexBoss, the GridBoss will go into rapid shutdown as soon as it is initiated.

How do you take a FlexBOSS offline and keep the GridBOSS up to keep power flowing from the grid?

Let's say you you want to service/replace the FlexBOSS but don't want to interrupt power. Grid is up, so you want the GridBOSS to pass grid to the loads while the FlexBOSS is off/disconnected.

If you press the RSD button on the FlexBOSS, the GridBOSS will kill power per above. So you can't do that. If you unwire RSD from the inverter, that's the same as pressing the RSD button. So you can't do that, either.

You can turn off the FlexBOSS breaker in the GridBOSS, but that doesn't turn off the FlexBOSS, does it? If there is PV or battery, the power is still hot.

It seemed to me one of the features the GridBOSS should provide is that ability to stay in service while the inverter is offline, but I'm not sure how one does that given the RSD/power dependency between them.

Can EG4 explain the process of serving a FlexBOSS without shutting down power through a GridBOSS? Or is the GridBOSS unable to do that?

Mike C.

 

[Brucey]

Can EG4 explain the process of serving a FlexBOSS without shutting down power through a GridBOSS? Or is the GridBOSS unable to do that?

Isn't there a physical bypass on the gridboss to take it out of the the loop? Then turn off the 70A inverter breaker and replace flexboss?

 

[mciholas]

Isn't there a physical bypass on the gridboss to take it out of the the loop? Then turn off the 70A inverter breaker and replace flexboss?

That does, briefly, interrupt power as you reconfigure the bypass breakers.

Seems like there should be a way to keep power going and isolate the FlexBOSS for service.

All that would be needed is to decouple the RSD between devices. Then you could turn off the FlexBOSS, turn off the inverter breaker in the GridBOSS, and you are good to go. The problem is RSD takes out the GridBOSS, too.

Why does RSD take out the GridBOSS? I see no reason it should. It can't, by itself, produce power from PV or battery. If all the FlexBOSS units are RSD'ed, then isn't that enough?

Mike C.

 

[obsoletion]

I agree it should not take down the grid boss. With that said you can flip the bypass breaker on to stay on grid and bypass the grid boss

 

[CaySol]

That does, briefly, interrupt power as you reconfigure the bypass breakers.

Seems like there should be a way to keep power going and isolate the FlexBOSS for service.

All that would be needed is to decouple the RSD between devices. Then you could turn off the FlexBOSS, turn off the inverter breaker in the GridBOSS, and you are good to go. The problem is RSD takes out the GridBOSS, too.

Why does RSD take out the GridBOSS? I see no reason it should. It can't, by itself, produce power from PV or battery. If all the FlexBOSS units are RSD'ed, then isn't that enough?

Mike C.

Turn off the hybrid breakers on the grid boss. Turn off batteries and battery breaker on the Flexboss and turn the Pv disconnect to off on the Flexboss. It will throw an error but backup power will not be interrupted.

 

[Quattrohead]

Bypass breaker on the grid boss, specifically added after the prototype for this very reason. You can thank us beta testers for this

 

[mciholas]

Turn off the hybrid breakers on the grid boss. Turn off batteries and battery breaker on the Flexboss and turn the Pv disconnect to off on the Flexboss. It will throw an error but backup power will not be interrupted.

Isn't the FlexBOSS RSD 12 volts tied to the GridBOSS? If you remove those wires from the FlexBOSS, won't it shutdown the GridBOSS?

The RSD wiring diagram implies any interruption of the RSD wiring to the master FlexBOSS will also shutdown the GridBOSS.




Mike C.

 

[skimandan]

I can't find the details of your 4 PV panel string, can you tell us which panels they are and if you have any RSD/optimizers attached to this string.

Enjoy!
https://diysolarforum.com/threads/flexboss21-error.98378/
I now know the manual states it will work optimally with "hints" that it won't work nominally. The string sizer tool gave it a yes, then EG4 later revised it to say maybe only in cold weather after I ordered my panels. I think people use the word "maximal" as well. Perhaps word salads sell inverters. And I had to block at least one forum user for being a meany.

 

[skimandan]

1. Many of the settings in the software do not do what you would expect. In order to keep my battery throughout the night I have to Activate A/C charge, then give a time period, then trickle charge the battery for the time period.

We will be reviewing this and posting settings that fit your needs.

2. FlexBoss21 Optimal string voltage is claimed to be 120V-440, but does not appear to work even when string voltage is higher than 140V. This is costing me production I was planning on. https://diysolarforum.com/threads/flexboss21-error.98378/

Operation voltage is between 120-440VDC. However, nominal voltage is at 360VDC.

View attachment 275944

3. GridBoss may not be able to handle high pass through current from the Grid. Awaiting resolution. Resolved in beta firmware provided to SlowRoller 2/2/2025. https://diysolarforum.com/threads/gridboss-with-flexboss-not-handling-21kw-pass-through.97560/

This will be addressed on our next firmware update.

4. Pressing RSD button on FlexBoss21 shuts down GridBoss backup load even though the grid connection remains active. Not user configurable. 2/5/25 EG4 Tech confirmed this is intended.

When in parallel with the FlexBoss, the GridBoss will go into rapid shutdown as soon as it is initiated.


5. GridBoss Smart Ports - Signature Solar Tech warned me the Smart Ports may not work in a grid down scenario when I was asking how to set it up with my EV charger.

Smart Ports will work in a grid down scenario.

6. Time of Use settings described on page 45 of the FlexBoss21 settings do not exist in the inverter settings. Requires workarounds to enact and the techs were unable to create enough workarounds to meet my 3 pricing periods. Also unable to handle weekend pricing. https://diysolarforum.com/threads/flexboss-21-time-of-use-settings.98597/

TOU settings are for peak shaving, forced discharge, AC charging, and battery priority times. These are only configurable for TOU with 3 time slots available. We will be investigating whether adding a time and date time of use option will benefit our customers.


7. Web monitor does not provide picture of Flexboss21 when linked to Gridboss – its just a nebulous square.

We will be investigating this.

8. Copper only - this was well documented but nobody uses copper at 200A!

We currently have an application to have the GridBOSS certified for use with aluminum wiring.


9. To lower my PV starting voltage to 120V and received the same error code I encountered.

We will be investigating why this error code occurred.


10. He walked me through an undocumented configuration setting with my Indoor Wallmount batteries (set to brand 1 in the inverter instead of 0 EG4).

This chart is beneficial for the correct lithium brand and battery for our products.


View attachment 275945


Thank you again for your feedback as we work to make our documentation and products better for all users!

Thanks for taking these "new guy" issues seriously.

 

[skimandan]

I agree it should not take down the grid boss. With that said you can flip the bypass breaker on to stay on grid and bypass the grid boss

Only if you are home. I am looking for wife friendly redundancy.
Otherwise I have to rush home from my ski trip to keep the kids' guinea pigs from freezing to death. Ask me how I know!

 

[obsoletion]

Only if you are home. I am looking for wife friendly redundancy.
Otherwise I have to rush home from my ski trip to keep the kids' guinea pigs from freezing to death. Ask me how I know!

I totally get that - I travel and have a wife and 4 daughters.... I do try to keep it simple. I will add the bypass breakers to her understanding now that it is in my head.

 

[skimandan]

2. FlexBoss21 Optimal string voltage is claimed to be 120V-440, but does not appear to work even when string voltage is higher than 140V. This is costing me production I was planning on. https://diysolarforum.com/threads/flexboss21-error.98378/

Operation voltage is between 120-440VDC. However, nominal voltage is at 360VDC.

Hi there friend, this keeps coming across as blaming me for not knowing which of the published specs to believe while designing my system. You are grabbing one piece that defends what you want, but not the entire body of the manual. I grabbed ALL of the references to string voltage I could find from the entire manual and placed them in a single overwhelming post. I also attached the output from the EG4 string sizer tool from when I designed my system in December.

120V - 440V as optimal is stated multiple times. I have no idea what one is supposed to do with the nominal 360V rating. Why would anyone design for Nominal when there is Maximum and Optimal to shoot for?

Perhaps in solar world these words have different meanings, but I think this is what EG4 meant:
Maximum = the greatest quantity or value attainable or attained
Nominal = being according to plan
Optimal = most desirable or satisfactory
Words have meaning in the manual for a technical device. If over 120V I should be satisfied, if over 250V it should be greatest quantity. This is what I want.

 

[Brucey]

Hi there friend, this keeps coming across as blaming me for not knowing which of the published specs to believe while designing my system. You are grabbing one piece that defends what you want, but not the entire body of the manual. I grabbed ALL of the references to string voltage I could find from the entire manual and placed them in a single overwhelming post. I also attached the output from the EG4 string sizer tool from when I designed my system in December.

120V - 440V as optimal is stated multiple times. I have no idea what one is supposed to do with the nominal 360V rating. Why would anyone design for Nominal when there is Maximum and Optimal to shoot for?

Perhaps in solar world these words have different meanings, but I think this is what EG4 meant:
Maximum = the greatest quantity or value attainable or attained
Nominal = being according to plan
Optimal = most desirable or satisfactory
Words have meaning in the manual for a technical device. If over 120V I should be satisfied, if over 250V it should be greatest quantity. This is what I want.

View attachment 276041View attachment 276042View attachment 276043View attachment 276044View attachment 276045View attachment 276046

For whatever reason eg4 is hiding the full power mppt range in the current spec listing. This is what they used to list for the 18kpv, 230-500V.

Just plan for 230V minimum and accept that their string calculator and support staff no longer have access to this information. Its been buried.

 

[EG4TechSolutionsTeam]

For whatever reason eg4 is hiding the full power mppt range in the current spec listing. This is what they used to list for the 18kpv, 230-500V.

Just plan for 230V minimum and accept that their string calculator and support staff no longer have access to this information. Its been buried.

View attachment 276061

The recommendation and adjustment are based on the fact that, while the MPPT can accept power at the lower range, achieving more consistent and stable power delivery requires sizing the array within the 250-440VDC range, with a nominal voltage of approximately 360VDC. Field data has shown that this configuration provides optimal power delivery for PV systems.

 

[Brucey]

The recommendation and adjustment are based on the fact that, while the MPPT can accept power at the lower range, achieving more consistent and stable power delivery requires sizing the array within the 250-440VDC range, with a nominal voltage of approximately 360VDC. Field data has shown that this configuration provides optimal power delivery for PV systems.

Yes and that's the valuable information that should be on the spec sheet. So that owners equipment can run at optimum output, and string length can be properly configured. Five panels on the eg4 string calculator is not getting into that optimum voltage range.

 

[dotjpg]

Please let me know if I should make a new thread, but this was highly relevant to the MPPT voltage conversation here.

It sounds like the actually optimal voltage input per string on the Flexboss21 is 250-360V.

If I were to use these panels (https://signaturesolar.com/runergy-400w-bifacial-solar-panel-black-up-to-500w-with-bifacial-gain/), does that mean I would need a string of at minimum 7 panels (37.07V/panel) to hit 250V at Voc? It looks like according to the spec sheet I'd actually need at least 9 (29.82V/panel in power generating conditions) in series to approach the efficient range.

Unfortunately, I don't have the roof space (~35ft length) to fit 9 solar panels in a row. Would this mean that the Flexboss21 is an infeasible inverter for my setup? The 5 string capacity seemed extremely useful for my space-limited setup, but it seems like the panel/string minimum is quite a bit too large for my use case. The only way I could make it fit is if one string connected to panels both on the south and west sides of my roof, which as far as I can tell doesn't sound ideal.

Are there suggestions for high-voltage panels that could make the setup work? On Signature Solar there is exactly one set of high-voltage panels (https://signaturesolar.com/philadelphia-solar-550w-bifacial-solar-panel-ps-m144-hcbf-550w/) that could work with only 6 at maximum power voltage (42.19V), but it looks like...it'll only ship to customers who have business-sized loading docks?

It seems odd that the Flexboss21 has such a narrow range of acceptable string lengths. Would you suggest just going with a microinverter setup if I cannot fit 9-12 panels per string?