Best choice of GT inverter to work with GS8048

[koalamotorsport]

I have a pair of GS8048 (not A models) in a grid tie hybrid environment, and a huge excess of potential solar production.
My current array consists of 52 panels, rated at 14.6kw. However, I have another 175.5kw of panels in the shed, and while I'm pretty sure I can't fit them all on my 5 acres, I would certainly like to put at least 20 more up (5.7kw). Yes, I know it sounds crazy, but my average (annual) daily electric use is 95kWh if I use my propane boiler for heat and around 190kWh if I use my electric boiler (averages 350kWh per day during winter.....)

My battery bank is currently only 430ah, about to be increased to approx 1800ah. The 6 MX-60s are more than enough to charge 1800ah, so why spend more on charge controllers when I can just go AC coupled?

Question 1. Is there a preferred GT inverter to use? I know I need to stick to 6kw or less.
Question 2. As I have 2 Radians, can I feed each with a 6kw GT inverter?
Question 3. (unrelated) Can I run GS8048 and GS8048a inverters together? (almost ready to add a couple more to what I already have)

[sparksalot]

Cleveland I'm 1-1/2 hrs. from downtown..southeast or half way between Cleveland,OH and Pittsburgh, PA.

#1. (V)FXR Series of hybrid inverter, as all other series of inverters, except Radian, have been discontinued.

#2. VFXR Inverter output 120vac, so 2 w/ a hub10 and a Mate3 needed to output 240vac

#3. Not unless the firmware would match for both/all...they most likely are not the same in a GS8048 A and a non-A . Someone needs to confirm this for certain.

[koalamotorsport]

Thanks for taking the time to reply Sparksalot.

If you're ever heading through Hambden/Chardon area, let me know. Be glad to show you the system.

Outback power does not offer inverters for AC Coupling. Hence my question to the board, looking for recommendations such as Sunnyboy or whatever.
Using the Outback FXR units would defeat the purpose, as they require batteries, which in turn, require charge controllers.

[sparksalot]

Gotcha.

In that case, I've been seeing some really great pricing on SMA GT units and they are highly regarded in that market as well.

EDIT to add SMA inverter

[koalamotorsport]

I gotta say I'm surprised at the lack of views and comments on this one. Seems this forum has slowed down a lot since I was last a regular.

Sparksalot, thanks for the recommendation. We have a 75 amp Fronius power supply at the shop, to power cars while they are being programmed. It is an impressive piece of equipment.
Looking at their solar inverter offerings, I'm not sure they have a good match. The recommendation is to keep Radian input below 6Kw. That gives the Fronius Primo 6.0-1 6.0kW TL, but while it can handle up to 9300 watts, it's limits are 600V and 18 amps. My panels are 285W with around 45.5 VOC and 8.5 ISC, which means I can only run 24 panels in two strings of 12 panels through it. I'm looking to put 40 panels up on this side of the system, but would prefer to stick with one inverter. Even if I take ISC as an impossible event, the IMP of 7.95A still leaves me stuck at 24 panels.

Still looking.....

[sparksalot]

PM sent

[Kurt Lundquist]

Unless you lose grid power frequently I wouldn't bother with AC coupling the GT inverters to the OutBack system. My 2 cents.

-Kurt

[koalamotorsport]

Kurt, you have a valid point, and I will likely just direct grid tie the inverters for now, but I wanted to make sure I was able to switch to A/C coupling if needed.

There is a significant chance that the electric company will kick me off the grid at some point here, so I wanted to size everything accordingly for the change. I have a habit of over designing everything, for worst case scenario situations. It's never let me down yet. :) That's why I have 400A capability between the power house and the main house, with enough wall space in the power house for 8 Radians and 10,000 AH of batteries....

Sparksalot. Thanks for the suggestions. Ultimately, I found a pair of new old stock Fronius IG Advanced 6.0 units (that were replaced by the Primo) that can handle 28A at 600V. They will allow me to put up 40 panels with room to spare, and being 6kw, they can be A/C coupled to the Radian, safely.

[cyrax]

hi All.

I am little confused here concerning the Outback inverter rating. The Flexmax 70 or 80 are 7KVA or 7KW. which is the unit??

Kindly clarify

Besides My mate 3 is showing a load of 5.9 KW, is that really possible??

real power/ app power = power factor. using this i have a load in KW of 5.6

[SuperiorSolarVA]

You could go with Enphase microinverters, or any grid tied inverter for that matter, except for an outback as you said. Why even bother with AC coupled? Are you off grid? You could just sell back the excess PV and during an outage just operate on the system already tied to the CCs and battery bank. If you go AC coupled you'll need the ROCB (remote operated circuit breaker) attached to the Radian AUX output in order to safely turn off the AC coupled system when batts reach ~100%.

One question on this subject is let's say I have 12 kW of PV feeding a grid hybrid inverter / battery bank, and I expect to sell electricity more than 50% of the time, do I need two radian 8048s stacked in order to safely "sell" over 8kw of PV power?

Thanks,

[koalamotorsport]

hi All.

I am little confused here concerning the Outback inverter rating. The Flexmax 70 or 80 are 7KVA or 7KW. which is the unit??

Kindly clarify

kVA and kW are the same if you have a power factor of 1. Most houses would be very close to a power factor of 1. Transformers, motors, etc, are what cause the power factor to drop and therefore require more kVA to supply the desired kW. The power factor is necessary when determining wire size, or your generator size, solar system size, etc, but again, in most residential situations, the power factor is going to be very close to 1.0.

[koalamotorsport]

Unless you lose grid power frequently I wouldn't bother with AC coupling the GT inverters to the OutBack system. My 2 cents.

-Kurt

Kurt, here we are about 5 months later, and I've just ordered an ROCB kit to complete the A/C Coupling. As it turns out, running a hybrid system, and a grid tie system, on the same feed, is not viable.

Over the last 3 or 4 months that I've been running both, side by side, I've lost about 1000kWh of potential generation because the inverters get into a pissing match.

In order to sell, the inverters will push amperage at a slightly higher voltage than the current grid voltage. Well, when you have two systems tied to the same feed in close proximity, you end up with each system raising the voltage until one, or both, drop out due to high grid voltage. With the two separate systems running, I regularly hit 264V and have even managed to see over 280V when messing with settings to diagnose this.

So.... No, you can't do it. At least, not if both systems are connected to the feed in close proximity.

When my ROCB kit shows up, I'll correct this issue, then move on to the next phase of testing. I'm about to roof a new pole building that will then get 20 more panels. When I set that up, I'm going to run a direct grid tie inverter to the feed, but I'm going to do it over about 175ft of line, versus a literal side by side connection that I have been running. The assumption is that over that distance, it allows the loads to draw down the voltage. No idea of that theory is good, but will find out soon enough.

So, anyway, that brings me back to the other two original questions in my first post on this thread, neither of which, anyone has addressed thus far.
Question 2. As I have 2 Radians, can I feed each with a 6kw GT inverter?
Question 3. (unrelated) Can I run GS8048 and GS8048a inverters together? (almost ready to add a couple more to what I already have)

[koalamotorsport]

The plot thickens.

My ROCB kit arrives tomorrow so that I can A/C couple the currently grid tied inverter.

While waiting, I've had the opportunity to do a bunch of testing and found something that confuses me.

When I shut down all selling from both the Radians and the SMA, my grid is hovering around 239-242V. If I turn on the SMA grid tie inverter, it bumps the voltage to around 252V in order to sell. That's close enough to 10V increase.
But.... if I turn on the Radian sell feature, (with the SMA off, so same test, different inverter) it immediately jumps the voltage to 256V or more. an increase of about 16V.

Is that normal? It seems high to me, but I have nothing else to compare it to. I understand the point that it has to be higher than grid voltage to sell, but is 16V either necessary, or normal?

When I have both systems feeding the grid, the SMA keeps shutting down because I'll hit as high as 268V according to what is recorded in the Mate3 as high voltage for the day. Always at peak sun, around noon, when both systems are selling the hardest.

Also, I noticed that the mate voltage cannot be accurately calibrated. With the entire system at rest, no selling, the mate reading 240V, my DVOM reads 240V on the feed. As soon as the Radians start selling (still with the SMA turned off), the Mate shows about 5V higher than the DVOM. So, I see 256V on the DVOM but Mate shows 261V. The calibrate feature in the inverter section of the Mate3 settings allows me to adjust to true, at one end or the other, but then throws off the opposite end. So if I correct the V reading while selling, then it will rest at around 235V when the grid is actually at 240V per the DVOM. I have tried two DVOMs, one of which is a trusted professional FLUKE meter. I absolutely trust the fluke reading vs the mate reading.

Thoughts?
Thanks
Brett

[Farlander]

Are you absolutely sure that by using the Fronius grid tied to the same connection point as the Outback caused voltage competition and limited power output? Is your feeder back to the source sufficient ampacity for all that power?

[koalamotorsport]

Are you absolutely sure that by using the Fronius grid tied to the same connection point as the Outback caused voltage competition and limited power output? Is your feeder back to the source sufficient ampacity for all that power?

The feeder is 4/0 aluminum, rated for 200A.

At this point, I'm as positive as I can be until I can test it by going A/C Coupled. That would have been easier if Outback hadn't replaced the $230 A/C Coupling kit with a $10,000 inverter. I am currently waiting for an ROCB to be shipped from Carling to my local electrical distributor so that I can duplicate the discontinued Outback kit.

[Farlander]

In my experience a high voltage condition causing inverters to shut down means a bad connection or breaker not seated all the way. Multiple inverters in GT mode should not compete like that unless there is no way to shed excess power.

[koalamotorsport]

In my experience a high voltage condition causing inverters to shut down means a bad connection or breaker not seated all the way. Multiple inverters in GT mode should not compete like that unless there is no way to shed excess power.

Problem was also present with a Fronius inverter. I snagged an SMA because the Fronius was showing communication errors that their tech support couldn't work out. It seems that those were false faults related to the voltage issues I have.

The Fronius is still mounted, and still wired on the A/C side. So the SMA is on a different 50A breaker. The common denominator on the A/C side is a solid bus bar. Pretty hard to get that wrong, but on your suggestion, I disconnected, checked, and reconnected each wire. There were no issues there.

The "A/C in" bus bars are connected to the meter via approx. 175ft of 4/0 aluminum wire, which is way overkill for the 100A max capacity of the two Radians. As I'm typing this, I'm thinking about the breakers involved. The 4/0 goes through a 200A breaker in the power house, beside the Radians, and then through a 400A breaker in the main house, before it gets to the meter. I'll check those for voltage drops.

Thanks.
Brett