What VFXR settings are global vs per inverter?

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twistedtree
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What VFXR settings are global vs per inverter?

Post by twistedtree »

I have a 4 unit VFXR3524A system, set up as 240V split phase with a pair of slaves for each leg. I'm trying to get some clarity on which parameters are global for the stack of 4 inverters, which are semi-global for a particular leg, and which are per-inverter.

So let's take the battery charging parameters, like Absorb and Float voltage, and absorb time. Can I set those in just the master (port 1), and all the inverters will use that value? If so, that value doesn't propagate to the other units in ports 2,7,8). But maybe they are acting on the values from port 1 even though they appear to be programmed differently? Or does the charging algorithm in each inverter run independently using it's own settings, and and change that I make I need to be sure to program the same thing in each inverter?

Now let's take Charger amps that limits how many AC input amps the charger can draw. The manual is clear that the value is per-inverter, and that I need to divide the total value by 4 (I have 4 inverters) to get the per-inverter limit. And it further says that you only need to set the master (port 1) and the others will follow. That says I should program 10A into the Master (port 1).

But it doesn't seem to work that way. First off, with a split phase system, I think I want to divide the desired max by 2, not by 4. That would give each inverter 20A, two on L1 and 2 on L2 for a result of 40A @ 240V. Is that not correct?

Also, it appears that only setting the value in "the master" really means that you need to set it in each line or phase master. If I program 10A into Port 1, ports 1 and 2 limit to that value. The get ports 7,8 (line 2 in the split phase system) to operate I need to program the limit into the sub-phase master (port 7).

Can anyone clarify how this works?
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Re: What VFXR settings are global vs per inverter?

Post by raysun »

quote]
So let's take the battery charging parameters, like Absorb and Float voltage, and absorb time. Can I set those in just the master (port 1), and all the inverters will use that value? If so, that value doesn't propagate to the other units in ports 2,7,8). But maybe they are acting on the values from port 1 even though they appear to be programmed differently? Or does the charging algorithm in each inverter run independently using it's own settings, and and change that I make I need to be sure to program the same thing in each inverter?
[/quote]

All the inverter chargers are designed to operate autonomously. They need all parameters set such that each properly charges the battery.
Now let's take Charger amps that limits how many AC input amps the charger can draw. The manual is clear that the value is per-inverter, and that I need to divide the total value by 4 (I have 4 inverters) to get the per-inverter limit. And it further says that you only need to set the master (port 1) and the others will follow. That says I should program 10A into the Master (port 1).
The only "coordination" setting I am aware of is the minimum AC input current on the Master so that the Slaves can be enabled.

In stacking, the inverters share the AC Input total current, but the values are set individually. TBH, I've not set it for series stacked split phase, so can't speak to the behavior, but since each "half" is on L1 and L2, the setting *should* be with that in mind. If 240V 100A service is available, each of the 4 inverters would be set to 50A. (Trust but verify. I spent a lot of time sleeping in math class.)
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Mike Curran
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Re: What VFXR settings are global vs per inverter?

Post by Mike Curran »

The fxr manual says
The charging of stacked inverters is synchronized and is governed by the master. The voltage settings of other inverters are ignored. Slave and subphase masters use the master settings.
Screenshot_20211008-203945_Adobe Acrobat.jpg
https://smart.tigoenergy.com/p/pZXn7SZQyO45?date=2021-04-19
https://enlighten.enphaseenergy.com/public/systems/Hctc107221
raysun
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Re: What VFXR settings are global vs per inverter?

Post by raysun »

Mike Curran wrote: Fri Oct 08, 2021 5:42 pm The fxr manual says
The charging of stacked inverters is synchronized and is governed by the master. The voltage settings of other inverters are ignored. Slave and subphase masters use the master settings.
Screenshot_20211008-203945_Adobe Acrobat.jpg
Well RTFM wins again!

Thanks Mike. I'm going to try it. My dual FXRs didn't seem to work that way, but it was early in my setup, so I expect I was confused by what I thought I was seeing.
twistedtree
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Re: What VFXR settings are global vs per inverter?

Post by twistedtree »

Right, I read that, but it's not how it seems to work. If it did work that way, wouldn't all the inverters be charger or not charging at the same time? I've seen plenty of cases where this doesn't seem to be the case. But I'll pay closer attention to it, and perhaps experiment a bit.

On Charger Current limiting, here's what the manual says:

"If FXR inverters are stacked, the master inverter Charger AC Limit setting is used by all other inverters. Divide the total AC current by the number of chargers used and program the master with the result. The master will operate all chargers with this setting to achieve the maximum total charge current. The system display has a global Charger Control command of On which enables all available chargers."

This appears to actually be per-phase, or per-leg. So in a split phase system, the Master (which is the L1 master) controls itself and and L1 slaves. But it doesn't appear to control the L2 sub-phase master or any of the L2 slaves. It appears you need to also program the L2 Master, which in turn also controls the L2 Slaves. At least this is what I have observed so far.

Anyone else have direct experience with this?
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Re: What VFXR settings are global vs per inverter?

Post by raysun »

Anyone else have direct experience with this?
I think we're going to hear this from you.

For my off-grid parallel stacked FXR inverters, both (Gen) AC Input and Current Limit and Charger AC Limit are programmed individually.

The generator is rated at 30A continuous.

Master:
Gen Input AC Limit = 15A
Charger AC Limit = 14A

Slave
Gen Input AC Limit = 15A
Charger AC Limit = 14A

Both chargers contribute 50% of the charge current @ 3.4kW total.

If I change the Slave to Charger AC Limit = 7A, then the Master contributes 67% and the Slave 33%.
twistedtree
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Re: What VFXR settings are global vs per inverter?

Post by twistedtree »

So your system is 120V, not split phase?

Your experience seems to contradict what the manual says. As I read the manual, it says the slave should follow the setting of the master.

I wonder if Outback knows how this actually works?
raysun
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Re: What VFXR settings are global vs per inverter?

Post by raysun »

twistedtree wrote: Fri Oct 08, 2021 8:24 pm So your system is 120V, not split phase?

Your experience seems to contradict what the manual says. As I read the manual, it says the slave should follow the setting of the master.

I wonder if Outback knows how this actually works?
We leave split phase to the Sperry Top-Sider crowd. 😉 Out here in the lava rocks we are just single phase folks.

I do believe there are occasions where the immediacy of firmware updates may lead documentation updates by an indefinite interval. So, who knows what may depend on who and when you ask. Two fundamental truths apply:
"Real programmers don't write documentation. If it was hard to program it should be hard to understand"
-Programmers apocrypha
and
"Trust everybody, but always cut the cards."
-Kindly Old Uncle Wally
twistedtree
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Re: What VFXR settings are global vs per inverter?

Post by twistedtree »

OK, I don't think I'll touch any of that.....
raysun
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Re: What VFXR settings are global vs per inverter?

Post by raysun »

twistedtree wrote: Fri Oct 08, 2021 9:11 pm OK, I don't think I'll touch any of that.....
🤣🤣
raysun
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Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
Honda EU7000is gas fuel generator

Re: What VFXR settings are global vs per inverter?

Post by raysun »

At any rate, run the tests and post back here. This forum is the best documentation.

I'll repeat mine.
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