Solar PV to loads only - how does this work?

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mhspohr
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Posts: 40
Joined: Sun Jun 30, 2019 8:56 am
My RE system: 6.6 kW SolarWorld/Enphase and 2.6 kW Sunpower/SMA
Skybox with 10 kWh SLA (used for power outage backup only)
Tesla 2015 Model S 85D charged from the sun.

Solar PV to loads only - how does this work?

Post by mhspohr » Mon Jul 27, 2020 9:05 am

I'm finally getting solar panels connected to my Skybox (single string of 4.4 kW 12 panels) and I trying to think through how the power will flow.
My current (temporary) setup is as battery backup power only with no grid input.
If I don't connect the grid input to the Skybox, I assume the solar PV power will flow to the batteries and then to any loads I have connected. I assume the Skybox will regulate output to avoid overvoltage.
Is this correct?

fcwlp
Forum Guru
Posts: 475
Joined: Wed Jan 22, 2020 9:40 am
My RE system: GS8048A, FM80 w/3,600 W PV Fixed, FM80 w/2,700W on Zomeworks tracker, Mate3, 24 Trojan 2V L16 1100AH @ C20, Grid-Tied with Kohler 14RESA LPG Generator and MEP-803 Diesel if needed
I also install and maintain grid-tied and off-grid systems, details will be given for these system if required
Location: 80 miles NE of Phoenix at 5500'

Re: Solar PV to loads only - how does this work?

Post by fcwlp » Mon Jul 27, 2020 9:43 am

mhspohr wrote:
Mon Jul 27, 2020 9:05 am
If I don't connect the grid input to the Skybox, I assume the solar PV power will flow to the batteries and then to any loads I have connected.
Almost correct. The PV will charge the batteries and the batteries then supply the power to the inverter.
mhspohr wrote:
Mon Jul 27, 2020 9:05 am
I assume the Skybox will regulate output to avoid overvoltage.
Is this correct?
This is correct, if you have programmed the settings correctly.

mhspohr
Forum Whiz
Posts: 40
Joined: Sun Jun 30, 2019 8:56 am
My RE system: 6.6 kW SolarWorld/Enphase and 2.6 kW Sunpower/SMA
Skybox with 10 kWh SLA (used for power outage backup only)
Tesla 2015 Model S 85D charged from the sun.

Re: Solar PV to loads only - how does this work?

Post by mhspohr » Mon Jul 27, 2020 11:13 am

Thanks for this information.
Now if I connect the grid to the grid input of the Skybox or alternatively have my loads connected to the load center which is connected to the grid, will the inverter sync with the grid or will I get lots of sparks?
(Just looking at how to configure this for seamless power backup.)

Mike Curran
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Re: Solar PV to loads only - how does this work?

Post by Mike Curran » Mon Jul 27, 2020 12:03 pm

You cannot connect the grid to both the Skybox AC input and to the load panel (which I'm assuming is) connected to the Skybox AC output. This might cause sparks, or if you're lucky just give an error message and prevent the Skybox from sending any AC out.

All you need do is connect grid to the Skybox AC input. Your load panel must be isolated from the rest of your grid-connected circuits - in other words it must be a dedicated backed up loads panel, separate from other loads that are direct grid supplied.

Hope this makes sense. - Mike.
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

mhspohr
Forum Whiz
Posts: 40
Joined: Sun Jun 30, 2019 8:56 am
My RE system: 6.6 kW SolarWorld/Enphase and 2.6 kW Sunpower/SMA
Skybox with 10 kWh SLA (used for power outage backup only)
Tesla 2015 Model S 85D charged from the sun.

Re: Solar PV to loads only - how does this work?

Post by mhspohr » Mon Jul 27, 2020 12:13 pm

Great! Thanks for this.
I didn't think I could connect both the Skybox grid input and load output to the grid at the same time. Something told me this would lead to bad things.
It looks like I can connect the grid input to the Skybox and excess power will be exported to the grid. As long as I keep the loads separate, I can use them.

fcwlp
Forum Guru
Posts: 475
Joined: Wed Jan 22, 2020 9:40 am
My RE system: GS8048A, FM80 w/3,600 W PV Fixed, FM80 w/2,700W on Zomeworks tracker, Mate3, 24 Trojan 2V L16 1100AH @ C20, Grid-Tied with Kohler 14RESA LPG Generator and MEP-803 Diesel if needed
I also install and maintain grid-tied and off-grid systems, details will be given for these system if required
Location: 80 miles NE of Phoenix at 5500'

Re: Solar PV to loads only - how does this work?

Post by fcwlp » Mon Jul 27, 2020 12:33 pm

mhspohr wrote:
Mon Jul 27, 2020 12:13 pm
Great! Thanks for this.
I didn't think I could connect both the Skybox grid input and load output to the grid at the same time. Something told me this would lead to bad things.
It looks like I can connect the grid input to the Skybox and excess power will be exported to the grid. As long as I keep the loads separate, I can use them.
I got into the solar business because a friend did this and blew up two Schneider inverter boards. My guess is something similar would happen with OB products.

mhspohr
Forum Whiz
Posts: 40
Joined: Sun Jun 30, 2019 8:56 am
My RE system: 6.6 kW SolarWorld/Enphase and 2.6 kW Sunpower/SMA
Skybox with 10 kWh SLA (used for power outage backup only)
Tesla 2015 Model S 85D charged from the sun.

Re: Solar PV to loads only - how does this work?

Post by mhspohr » Mon Jul 27, 2020 12:48 pm

Nice to have both a Forum Guru and Forum Emperor help me sort things out.
Thanks very much!

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