EG4 GridBOSS Deep Dive

[FilterGuy]

The new EG4 Gridboss has had a lot of press, but since it is not just another inverter or battery, it deserves a deep dive into what it is, what it does and how it benefits the customer.
The bottom line is that it greatly reduces the cost and complexity of installations as well as adding more abilities around Generator connections, AC-Coupling, Smart loads and other features. However, to understand how those benefits are delivered, we must first understand what it is and what it does. Let's start with a block diagram:

 

[FilterGuy]

Now let’s look at the simplest possible setup using a GridBOSS


Edit: Added the following sentence based on questions later in this thread:
The Parallel Inverter Comms cable that goes between the inverter and the GridBOSS is not shown in the diagram. When the grid goes down, the GridBOSS isolates the system from the grid and the inverter(s) keep powering the loads.

At first Glance, it does not seem the GridBoss adds much, but that can be deceiving. Let’s compare a NEC-compliant install of a single inverter with and without GridBOSS

 

[FilterGuy]

Without GridBOSS


With GridBOSS
Edit: Corrected to show main breaker panel.



Notice that the GridBOSS replaces several boxes of switchgear and all the associated wiring. This can save a considerable amount of money on both Materials and Labor.

 

[FilterGuy]

• The benefits get even larger as you add more inverters, A generator, AC Couple, and Smart Loads.
• GridBOSS also offers the big advantage of being able to do Generator Input, AC Couple input and Smart loads. You are no longer forced to choose between them!
• With Gridboss, If you start with one inverter the growth path for additional inverters is extremely simple.

Without GridBOSS


WIth GridBOSS

Note: These diagrams are for the 18Kpv, but the layout would be identical for FlexBOSS 21 or 12Kpv

 

[FilterGuy]

The grid boss makes it easy to place the equipment where it needs to be. Only one circuit (sized to the inverter) is run between the GridBOSS and the Inverter.

 

[timselectric]

I think that people would like to know what happens when the grid goes down.
Since the inverters are grid-tied to the grid boss, does the grid boss override the export shutdown function, to keep everything running?

 

[FilterGuy]

I think that people would like to know what happens when the grid goes down.
Since the inverters are grid-tied to the grid boss, does the grid boss override the export shutdown function, to keep everything running?

Yes. When the Gridboss is employed, it takes over the Grid Disconnect function. When the Grid goes down, the Gridboos Grid Relay Isolates the system from the grid and the inverters keep powering the load.

 

[FilterGuy]

The parallel inverter communication cables extend to the GridBOSS so the inverters and the Gridboss all function as a system.

(The comms cables should have been shown in my diagrams above)

 

[timselectric]

Yes. When the Gridboss is employed, it takes over the Grid Disconnect function. When the Grid goes down, the Gridboos Grid Relay Isolates the system from the grid and the inverters keep powering the load.

Just to make sure that I understand correctly. The inverters will continue to export, even though they see no external power source on their grid port?

 

[42OhmsPA]

Yes. When the Gridboss is employed, it takes over the Grid Disconnect function. When the Grid goes down, the Gridboos Grid Relay Isolates the system from the grid and the inverters keep powering the load.

Is it fair to say, in layman's terms, that it's a fancy ATS / ATS on steroids?

 

[FilterGuy]

Just to make sure that I understand correctly. The inverters will continue to export, even though they see no external power source on their grid port?

Yes. When the grid goes down, the GridBOSS isolates the system from the Grid and the inverters switch from grid-interactive mode to Grid Forming mode (Offline Mode)

 

[timselectric]

Yes. When the grid goes down, the GridBOSS isolates the system from the Grid and the inverters switch from grid-interactive mode to Grid Forming mode (Offline Mode)

Thanks for the clarification.
I assume that if multiple inverters are connected, only one (master) switches to grid forming , and everything else follows.

Or maybe they synchronize and form together.

 

[FilterGuy]

Is it fair to say, in layman's terms, that it's a fancy ATS / ATS on steroids?

Yes, but I don't think of it that way. The industry name for it would be a Microgrid Interface Device. The primary purpose of a Mid is to isolate the system in the event of the grid going down. The driving force for creating it was to make installations much lower cost, but EG4 added a lot of additional features with the Smart Ports and Generator port.

 

[FilterGuy]

Thanks for the clarification.
I assume that if multiple inverters are connected, only one (master) switches to grid forming , and everything else follows.

The answer to the intent of the question is yes. However, I don't know how the inverters manage the grid-forming mode. I just know that they coordinate to do it. It seems like a logical conclusion that the master is defining the waveform and the others are following, but I don't know if that is done over the comms line or the slaves remain grid following.

 

[timselectric]

Also I believe that someone said that the 18kpv and 12kpv can be connected in the same way to the grid boss. I guess that they will need a different firmware (or update) to function this way?

 

[FilterGuy]

Also I believe that someone said that the 18kpv and 12kpv can be connected in the same way to the grid boss. I guess that they will need a different firmware (or update) to function this way?

Yes. All of the EG4 Hybrid inverters will work with the GridBOSS and Yes, Firmware Updates will be needed.

 

[goodoleme]

This works just like the Schneider 6848 pro with the BCS, just no smart ports.

 

[wpns]

So just because I've got a weird configuration, and because it's useful to understand all the ways the GridBoss can be used, can I have:

In my 'power house', solar panels, inverters, batteries, a Grid Boss, the Utility Meter, and some loads, including Smart Loads.

_Way_ over there, 450 feet away, the main house with another Grid Boss, another inverter with batteries (maybe no panels, could be just an ESS to help with surges), and most of the other loads, including four (more) Smart Loads?

Does that make any sense?

 

[timselectric]

So just because I've got a weird configuration, and because it's useful to understand all the ways the GridBoss can be used, can I have:

In my 'power house', solar panels, inverters, batteries, a Grid Boss, the Utility Meter, and some loads, including Smart Loads.

_Way_ over there, 450 feet away, the main house with another Grid Boss, another inverter with batteries (maybe no panels, could be just an ESS to help with surges), and most of the other loads, including four (more) Smart Loads?

Does that make any sense?

I can't imagine why not. As long as you don't try to make the two systems communicate.

 

[1201]

Yes. When the Gridboss is employed, it takes over the Grid Disconnect function. When the Grid goes down, the Gridboos Grid Relay Isolates the system from the grid and the inverters keep powering the load.

The grid boss appears to have both backed up loads and non backed up loads output.


Will the non backup loads still be powered when the grid is down?

 

[goodoleme]

The grid boss appears to have both backed up loads and non backed up loads output.

I presume the non backed up loads output is connected to the main panel.

Will the main panel(non backed up loads) still be powered when the grid is down?

No, the relay opens (1741).

 

[FilterGuy]

The grid boss appears to have both backed up loads and non backed up loads output.

I presume the non backed up loads output is connected to the main panel.

Will the main panel(non backed up loads) still be powered when the grid is down?

The Non Backed-up load port is connected to the Grid Breaker


In a typical install, the Grid port is directly hooked to the meter (or an independent grid disconnect). The main panel is driven by the GridBoss Load port.

 

[FilterGuy]

Will the non backup loads still be powered when the grid is down?

No - That is kinda the definition of 'Non Backed Up"

 

[1201]

No, the relay opens (1741).

Ok copy that. I downloaded the manual and that is confirmed on page 22.

So it means if one wants to run a main 200a panel with whole house backup then that panel has to go on the backup output.

 

[FilterGuy]

So it means if one wants to run a main 200a panel with whole house backup then that panel has to go on the backup output

Yes. That is the intended design.