AC coupling wiring diagram

[rs50pilot]

I have 32 modules connected to enphase Iq7+ inverters that are grid tied. 50 kwh of lithium batteries. I want to try to AC couple 6 modules for now.

Can someone give me a wiring diagram for this? I'm assuming I'll need a critical loads panel. I'm using a 10 circuit protrans transfer switch now.

My rosie is used for load shedding and emergency back up. If grid sell was an option I would run as much of my system through Rosie as possible so I'll have solar when the grid goes down.

Right now I don't want to do that because I'll be wasting energy that I can't send back to the grid.

[ClassicCrazy]

I don't see not using extra power that you don't need as wasting it .
Dave Jones made a video about ac coupling his enphase inverters recently . It is more of a block diagram of his system but maybe your Rosie can accomplish the same thing as he wants to do?
https://youtu.be/gAu8CvMjDrU?si=5UkpI1bQYnNMdvv2
Larry

[rs50pilot]

Thanks, but the way he has it wired I don't believe it will turn the enphase inverters on when the grid goes down.

You would need two ac inputs I believe.  Rosie doesn't have two AC inputs. I believe I have to land my enphase inverters to a box that has my back up loads wired to it.

Where does the ac input from the grid come from then? My main panel? If the grid goes down rosie needs to frequency shift to turn the ac coupled inverters on. That will make the backup panel live and be isolated from the grid.

I am not sure that is 100% correct. There isn't any info from midnite on how to do this.

[aaapilot]

Is your 10 circuit protrans the type that has the switches so you can use utility or inverter/generator power?

Dave

[aaapilot]

If your Protrans looks like the one below, it's easy to incorporate your 6 panel Enphase wiring.  I AC coupled using a string inverter and this panel.  The first 2 breakers (on the left side) are tied together for 240v and that's where you wire in your Enphase.  The other 8 circuits are backup circuits.  When utility power fails, ROSIE automatically powers the circuits in your backup panel.  If you wish to AC couple, you move the switch that controls the Enphase from the utility side to the inverter side. Your Enphase will see the ROSIE 'grid' AC power and should function as normal, providing AC source power to the backup panel as well as charge any batteries connected to the Rosie.  Once the batteries are full and all backup loads are satisfied, the DC voltage will rise to a point that Rosie begins to frequency shift to shutdown the incoming power from the Enphase inverters to keep the incoming power in check w/the loads.  ONE BIG CAUTION ****  Since Rosie is not capable of selling back power to the grid (soon maybe), I don't know what would happen when Utility power is restored and Rosie returns to passing thru Utility power to the backup panel WITH the Enphase still connected! ( Any input from Midnite folks would be appreciated!)  If/When Rosie sells back power, power would simply flow to the Utility.  You COULD turn OFF the Rosie INPUT breaker when power fails and you wish to AC couple, then when Utility power is restored, you First move the Enphase switch to the Utility position, then restore the Rosie INPUT breaker to on.  Once the Rosie adds Grid Sell to the firmware, you would not have to do this additional step.

As for 2 inputs into Rosie, I use a GE ON/OFF/ON switch as seen in the second photo.  The up position was for Utility power input & down position for Generator input.  You can't have both at once, just one at a time.  These pictures were from my previous system that used a Magnum PAE 48v inverter which was also capable of AC coupling. Hope this helps.

Dave
 

[rs50pilot]

I have the same protrans, enphase is connected to the line side of my main panel, not to a circuit breaker in it. Transfer switch is wired per its manual. I do not use a critical loads panel. I also use a three way switch as you do, second position is generator if needed.

Suppose I could put the enphase on the Generator position if grid goes down that would work I think.

I would like to have it automatic, so I can just leave those 6 or however many I decide connected all the time. Seems like without sell back I'm  out of luck. I thought Rosie's advancements would be released faster. Seems like she's on the back burner since the AIO has been released.

Let's say I did wire 6 panels to the gen side of my three way switch. Grid goes down, I throw the switch will Rosie turn on my inverters?

Grid comes back, these six will still be producing. When the main system comes back online switch to "grid" position and all is back to normal and the 6 will shutdown.

Thinking about it. I could run another switch were I could switch all of my enphase from grid, to the gen position. 
So grid goes down, throw two switches and my whole system would be off grid. Does this sound correct? Maybe I'm over thinking it.

[aaapilot]

Suppose I could put the enphase on the Generator position if grid goes down that would work I think.

Let's say I did wire 6 panels to the gen side of my three way switch. Grid goes down, I throw the switch will Rosie turn on my inverters?

I don't think this will work.  Your Enphase or a String tied inverters needs to 'SEE' grid power before turning on.  This protects lineman from your inverter back feeding the Utility lines when power is out and they are working on restoration.  SO, connecting to Rosie Input does nothing.  The way AC Coupling works is that Rosie Output now becomes the GRID for your Enphase inverters need to 'SEE' in order to turn on, so the Enphase must connect to Rosie's output, i.e. the backup circuit breaker panel.  As for keeping the 6 connected all the time, I would need a Midnite Rep to chime in as to what happens if your Enphase are connected to the backup panel when Utility power is normal and 'passing thru' to the backup panel.  The Rosie manual doesn't really address AC Coupling in detail, other than to say it works.

Dave

[rs50pilot]

I thought the inverter (rosie) was supposed to make the "grid" so the inverters will turn on.

In my double switch scenario,  rosie should form the grid so it should work. I think.

Unless I'm not understanding how an inverter uses ac coupling when off grid.

[aaapilot]

If you provide a diagram of your existing system, we might be able to guide you better.

You mentioned 'the way he has it wired' in an earlier post. Perhaps you might touch bases with the person that wired your existing system and discuss your plan for AC Grid tie, they might have some insight since they already know your system.

Dave

[rs50pilot]

If I could find a easy program to use to draw it that would be better than my chicken scratch drawing.

I installed the whole system so we don't have to ask anyone:).

It's pretty simple though.  Enphase comes off of the roof in three strings. Two have the max of 13 modules and then one string of 6. They going the enphase combiner box. From there they are connected directly to the buss bars of my main panel on the grid side of the main breaker.

There is a main disconnect between the combiner and the mains connection.

A 60amp breaker in the main panel goes into my two way switch (grid or gen) and the feeds rosie.

The protrans is connected to 10 circuits as stated in the manual.

I have 125a service with a NEM contract with PGe.

It is a simple as I could make it. I did everything on my own after reading everything I could.

I bought Rosie for it's light weight and American made form.

Also I did not have to buy 240v gen as she will take 120 in and go 240 out. Beautiful.

I just wish they would update the manual and make it so Rosie would charge more than once in a 24hr period. That is annoying but is another topic.

[rs50pilot]

Still nothing from Midnite people? I'm trying to save a call to tech support. Seems like Midnite doesn't watch any forum.

[Wizbandit]

Still nothing from Midnite people? I'm trying to save a call to tech support. Seems like Midnite doesn't watch any forum.

Sure we do.  Ac Coupling is as easy as moving up to 7000 watts of micro inverters to a breaker in a critical loads panel on Rosie's AC OUT.  Set "AC COUPLING" to "ON" in the SETUP>>SYSTEM CONFIG menu.  Now if you have Charge Controllers charging your battery and the grid goes down the micro inverters will only provide power to the loads if needed otherwise they will be throttled back using FSPC aka Frequency Shift Power Control.

This could make your clocks run fast as I'm not sure Rosie Engineers followed SMA's design exactly where SMA would keep track of how long the 60 Hz was at between 61 and 62 Hz and drop back the Frequency to 58 Hz for the calculated time to bring the clocks back to the right time. I need to ask...

[aaapilot]

Ac Coupling is as easy as moving up to 7000 watts of micro inverters to a breaker in a critical loads panel on Rosie's AC OUT.  Set "AC COUPLING" to "ON" in the SETUP>>SYSTEM CONFIG menu.  Now if you have Charge Controllers charging your battery and the grid goes down the micro inverters will only provide power to the loads if needed otherwise they will be throttled back using FSPC aka Frequency Shift Power Control.

Hey James, couple of questions regarding this scenario. 1) What happens if this Rosie is Grid-Tied and Utility power is normal/ON?  You have Utility power on the AC IN and Enphase AC input to the back-up panel? 2) If the AC power can co-exist in the first scenario (I'm guessing via FSPC), could you activate Grid Sell and the Enphase AC power would back flow to the Utility?  Thanks!

Dave