Final resolution: 600 watts at idle

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Mike Curran
Forum Emperor
Posts: 3235
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof (2007/2017):
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied VFXR3524A-01's series stacked, replaced GVFX's (2020)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS. Tigo ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 24 (2x12) 235W Lightways panels with Enphase M215 microinverters plus 6 - 275W Talesun panels, also with M215s, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Trina Solar 270W in series (DC array input to SB inverter/charger), currently awaiting installation (2/19/24)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input from 14 Talesun 275W (manually switched during outages), Enphase M215 microinverters

Battery systems operate in grid-tied, net metering w/backup mode
All self-designed and self-installed
Location: Chagrin Falls, Ohio

Final resolution: 600 watts at idle

Post by Mike Curran »

In this thread viewtopic.php?f=47&t=14520&hilit=200+watts I added my tale of woe to mhspohr's regarding my Skybox's high grid use at idle, no loads, mainly nighttime when there's no sun. This was over a year ago, and at that time I opened a case with OB Tech support.

Well, it's taken them awhile, but they finally figured out what's been going on. Somehow they came up with the idea that my grid input AC waveform is distorted. Whoda thunk it? Here's how Kim Foster of OB Tech support explains it:
When connected to the grid, but not contributing to the loads or producing PV power the SkyBox is a "pure" voltage source trying to maintain zero current. When the grid voltage waveform is distorted, there are sections where the SkyBox voltage waveform is higher or lower than the grid voltage waveform. In these cases, current flows between the grid and the SkyBox. This would be what you are seeing* on your clamp-on meter. Overall however, the current averages zero, which is what the SkyBox is showing with its zeroed load tile.
*Note I also saw this on Optics dashboard as grid use in the neighborhood of 500-600 watts.

Kim suggested that I check this with an oscilloscope. The attached screenshot shows my grid AC input waveform in red, and Skybox's AC output (to my critical loads panel) in yellow. It clearly shows the distortion in the grid. Why is it there? Who knows? All I know is my Skybox isn't really using 600 watts at idle. I believe what I'm seeing is called "apparent" power.

KUDOS to Kim and her team at Outback Technical Support.
https://drive.google.com/file/d/1UfnhZc ... sp=sharing
https://ei.tigoenergy.com/p/pZXn7SZQyO45
https://enlighten.enphaseenergy.com/public/systems/Hctc107221
As of 8/25/23 Westinghouse array down to 21 panels, Skybox DC array out of commission.
raysun
Forum Overlord
Posts: 10766
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Series Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Final resolution: 600 watts at idle

Post by raysun »

Egads! I'm glad I'm off-grid and only have sky, no Skybox.

We would be at the far end of the line, literally, with HELCO, our electric utility and the juice here is raggedy. I can just imagine how a Skybox would react with a waveform like this:
20210201_170509.jpg
sbrownian
Forum Czar
Posts: 661
Joined: Mon Nov 30, 2020 9:23 am
My RE system: GS8048 FM80 FNDC Mate3 4 port HUB
4kw solar
7kw Kubota propane gen
Off grid.
Originally installed with 1200 AH of FLA Locomotive batts.
Replaced after 9 years of service with 2 x 300 AH ReLion Lithium packs.
MUCH more efficient!!
Location: Central Washington State

Re: Final resolution: 600 watts at idle

Post by sbrownian »

Check it with a true RMS meter.

Also, "apparent power" can also be due to a phase shift between current and the voltage. (AKA 'power factor' or volt ampere reactive.)

If you can get a set of CTs, see what the phase relationship is between the current and the voltage.

Even a set of clip on set of 'clothes pin' style current transformers will work.

I remember someone (raysun?) mentioning the outback gear presents watts as VAR, not RMS...
Information, you get not; if incorrect question, you ask..
raysun
Forum Overlord
Posts: 10766
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Series Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Final resolution: 600 watts at idle

Post by raysun »

I remember someone (raysun?) mentioning the outback gear presents watts as VAR, not RMS...
I was corrected that I didn't want to say VAR, just VA. The OB gear deals in VA in the AC side of the street.
sbrownian
Forum Czar
Posts: 661
Joined: Mon Nov 30, 2020 9:23 am
My RE system: GS8048 FM80 FNDC Mate3 4 port HUB
4kw solar
7kw Kubota propane gen
Off grid.
Originally installed with 1200 AH of FLA Locomotive batts.
Replaced after 9 years of service with 2 x 300 AH ReLion Lithium packs.
MUCH more efficient!!
Location: Central Washington State

Re: Final resolution: 600 watts at idle

Post by sbrownian »

raysun wrote: Mon Feb 01, 2021 10:31 pm
I remember someone (raysun?) mentioning the outback gear presents watts as VAR, not RMS...
I was corrected that I didn't want to say VAR, just VA. The OB gear deals in VA in the AC side of the street.
Might be interesting to put a phase angle meter on it.
Information, you get not; if incorrect question, you ask..
The Electron
Forum Guru
Posts: 288
Joined: Thu Dec 14, 2006 3:08 pm
My RE system: I troubleshoot & maintain off-grid systems in many different scenarios, a few are total redneck messes I stumble across, some are pretty nice. Experience with multiple stacked FX's and Radians & Optics
Location: Northwest Montana

Re: Final resolution: 600 watts at idle

Post by The Electron »

What an interesting story these two threads ( viewtopic.php?t=14520 ) were to read! A gentle nudge to see what all shakes loose on the tree of inaccurate OB AC current/wattage reporting across all inverter models (feel free to start a new thread wherever appropriate).

One known example is 5 stacked 48v Radians at 120/240 with the AC input(only one input used on each inverter) having two gensets (50K and 60K Kohlers) fed into a 200A transfer switch. Both the inverters and genset monitoring software show lopsided (L1 - L2) site loads when using one genset but not the other-- but that genset has a roundabout way it's output makes it to the manual transfer switch. Spurious emissions/inductive 'interference' in parallel AC runs will def make for false readings with these inverters (any other known threads about this here?) Tnx all!
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