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Need an advice to select GS4048 or GS8048

Posted: Tue Nov 19, 2019 3:46 pm
by mkimid
Hi,

I have a plan to add an AC coupled back-up on my GTI system.
I have installed sub-panel (for essential power), the peak load usage should be 0.1~3kW
and, I have 320W(OTI inverter output) x 16 panel = ~5kW

for the back-up system, I have expected that GS4048 is more than enough for me when consider my essential power load,
But, I found two issues

(1) if the load is used in a hot line, such as only one line L1 or L2, maybe inverter output power is going HALF as 2kW. is it correct ?
I found, 16.7AAC is a maximum continuous power, 16.7AAC * 120V = ~2kW

(2) Even I made a good balance, I found 2nd problem. the maximum utility interactive current is 15A (3.1kW).
GRID is ON, and PV generate ~5kW in peak, Maybe GS4048 can not sell whole current.
or Can sell UPTO 50A (limit of bypass relay contact rate) ?

AC coupled system cost with GS4048 is ~$3k, and GS8048 is ~6k. It is too big difference even I need < 3kW essential power load for backup

Could you give me an advice about it ?

Re: Need an advice to select GS4048 or GS8048

Posted: Tue Nov 19, 2019 4:40 pm
by EMCF
What is the brand of your GT inverter? One thing you need to ask around is if your kind of GT inverter plays well with a Radian(GS) inverter. The other thing is, one of the requirements is the Outback inverter must be of higher capacity than the GT inverter. In their application note example,Radian GS8048A rated at 8kW was paired (AC Coupled) with a 6 kW grid tie inverter. You should comply with the ratio along that example.

Re: Need an advice to select GS4048 or GS8048

Posted: Tue Nov 19, 2019 4:53 pm
by Mike Curran
Looking at the gs4048/8048 manual, it appears you're right about the max power output from either L1 or L2:
Screenshot_20191119-192815.jpg
As far as max PV input from an AC - coupled array, per OB's app note on AC coupling, it looks like it's 6kw:
Screenshot_20191119-194232.jpg
Here's links to the pertinent documents: http://outbackpower.com/downloads/docum ... p_note.pdf

http://outbackpower.com/downloads/docum ... erator.pdf

Re: Need an advice to select GS4048 or GS8048

Posted: Wed Nov 20, 2019 9:53 am
by mkimid
EMCF wrote:
Tue Nov 19, 2019 4:40 pm
What is the brand of your GT inverter? One thing you need to ask around is if your kind of GT inverter plays well with a Radian(GS) inverter. The other thing is, one of the requirements is the Outback inverter must be of higher capacity than the GT inverter. In their application note example,Radian GS8048A rated at 8kW was paired (AC Coupled) with a 6 kW grid tie inverter. You should comply with the ratio along that example.
I have installed SunPower X21-350-D-AC panels (I feel it is enphase ODM, but maybe Subpower own band),
16 x 320W (maximum inverter power) = 5.12kW, Practically little under 5kW in my measurements.

It has connected on essential power panel, my essential power usage is peak ~3kW, general usage 1~2kW, and < 0.1kW most of time.

Thank you for your advice,

Re: Need an advice to select GS4048 or GS8048

Posted: Wed Nov 20, 2019 9:58 am
by mkimid
Mike Curran wrote:
Tue Nov 19, 2019 4:53 pm
Looking at the gs4048/8048 manual, it appears you're right about the max power output from either L1 or L2:Screenshot_20191119-192815.jpgAs far as max PV input from an AC - coupled array, per OB's app note on AC coupling, it looks like it's 6kw:Screenshot_20191119-194232.jpg
Here's links to the pertinent documents: http://outbackpower.com/downloads/docum ... p_note.pdf

http://outbackpower.com/downloads/docum ... erator.pdf
I feel, practical spec for 4048/8048

GTI 3kW 6kW
Line Power 2kW 4kW

Maybe, I have to find the other method even a manual connections,
but, it is hard to find a battery charger which can charge the battery from GTI Solar Power Source [unstable],
do you have any idea ?

Re: Need an advice to select GS4048 or GS8048

Posted: Wed Nov 20, 2019 11:42 am
by Mike Curran
it is hard to find a battery charger which can charge the battery from GTI Solar Power Source [unstable]
So, you're saying your grid-tie AC modules are so "unstable" that the OB inverter won't invert it to charge your battery? How big is the battery, amphours? FWIW, unless there's some problem with your AC modules' output, seems like a 4048 would be perfectly adequate for you.

Edit: My impression from the app note is that both the 4048 and the 8048 will accept up to 6kw of AC coupled input, since the note only refers to the Radian and not to a particular variant of it.

Re: Need an advice to select GS4048 or GS8048

Posted: Mon Jan 20, 2020 10:34 am
by IanMcCluskey
I am moving all threads related to AC Coupling to the new AC Coupling forum, and I notice the last post on here is incorrect.

We warranty up to 75% of the Radian(s) rating in AC Coupled inverter output.
Example 1 - GS4048A with twelve 250W micro inverters, or 3,000 W total
Example 2 - GS8048A with 1 6,000W grid dependent string inverter
Example 3 - Four GS8048A with three 7,600 W grid dependent inverters, or 22,800 W total