On grid and Off grid using SolarEdge and Growatt

John Schmidt

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Dec 30, 2020
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I'm annoyed that I can't use my 1-year old SolarEdge inverter without a grid connection, but need to live with it! I've purchased a GroWatt inverter to use when the grid goes down. If you have some time, please comment on the system that I plan on adding to my current on-grid system. I'm using a DPDT switch to switch between the SolarEdge inverter and the Growatt inverter. Any suggestions or ideas are great appreciated! If this works, I'll post the final design. Thank-you. See attached diagrams.
 

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macheung

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May 31, 2021
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Interesting, I was thinking of something very similar. It sucks that the optimizer are mandatory for Solaredge and they shut off when the grid goes down.

What kind of switch are you using to switch the panels from the optimizer to the off-grid inverter? I was thinking of using a series of automotive 50A 12V relays, avoid having to go on the roof to flip the switch or running heavy/expensive wires down to the inverter

Actually, do you think that DPDT switch or relay is even necessary? Or would it be possible to wire that in a Y and connect the panel to both the optimizes and the off grid inverter? The off grid inverter will not normally be connected until the grid is out, and when that happens, the solar edge optimizes should shut down and act almost like an open circuit. At which point you can manually connect the off grid inverter. When the power comes back on, you would disconnect the off grid inverter. The only thing that needs to be confirmed that if both the optimizer and inverter are connected, they would interact in a harmful way aside from lack of performance.
 
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2009Bounder2020

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im still not understanding the benefit to being grid connected. Why bother connecting to the grid? When we went solar it made it alot more complicated and the equipment is more expensive if we wanted to keep it grid connected, You save on batterys, but as you see its totally usless when the grid goes down. . You will still have minimum power bill monthly if your connected to the grid. I'm sure there is a reason people do it, but have not seen a financial benefit to it. We have a farm so maybe its a city code thing?
 

macheung

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im still not understanding the benefit to being grid connected. Why bother connecting to the grid? When we went solar it made it alot more complicated and the equipment is more expensive if we wanted to keep it grid connected, You save on batterys, but as you see its totally usless when the grid goes down. . You will still have minimum power bill monthly if your connected to the grid. I'm sure there is a reason people do it, but have not seen a financial benefit to it. We have a farm so maybe its a city code thing?
The grid is good 99.7% of the time in my area, and you would need a huge amount of batteries and massively oversized array to achieve that kind of reliability if totally off grid - you have to account for days of cloudy weather in winter. Connecting to the grid with the right net metering arrangement allows you to bank excess power in the sunny summer days and draw from the grid during the cloudy or winter days. So you can get by nearly net 0 with 1x your consumption, and don't have to oversize to like 3x panel with massive storage just to have reliable power.
 
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Cheap 4-life

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Jan 20, 2021
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im still not understanding the benefit to being grid connected. Why bother connecting to the grid? When we went solar it made it alot more complicated and the equipment is more expensive if we wanted to keep it grid connected, You save on batterys, but as you see its totally usless when the grid goes down. . You will still have minimum power bill monthly if your connected to the grid. I'm sure there is a reason people do it, but have not seen a financial benefit to it. We have a farm so maybe its a city code thing?
I’m connected to the grid because it’s almost always available in my area. Being on grid allows my system to perform like a much larger system because surges and loads that are over my inverters max output are covered by the grid. This is easier on the inverters and batteries. The grid tie inverters keep supplying their max output even if loads exceed the max output of the inverters. No transfer switches. Smaller solar array that covers most of the homes loads. My grid tie inverters also use batteries if solar cannot fully cover the homes load. Batteries allow me to save the excess power (during the day) from pv panels. I don’t have a lot of load during the day. Sending power into the grid, in my area costs almost a small fortune with lots of hoops to jump through. Long lasting lithium batteries are cheaper these days. Also with batteries I can use a small offgrid inverter to power my critical loads panel during the very rare power outage. Yes I still pay a small fee for the power hookup from the electric company, but I’m saving a minimum of $100 month. So basically an ongrid system can cost a lot less and still covers the majority of the homes loads, and in my case with my inverters still use batteries so I still have offgrid power with a separate small offgrid inverter.
 

John Schmidt

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Dec 30, 2020
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36
im still not understanding the benefit to being grid connected. Why bother connecting to the grid? When we went solar it made it alot more complicated and the equipment is more expensive if we wanted to keep it grid connected, You save on batterys, but as you see its totally usless when the grid goes down. . You will still have minimum power bill monthly if your connected to the grid. I'm sure there is a reason people do it, but have not seen a financial benefit to it. We have a farm so maybe its a city code thing?
We use too much power to be off grid 100%. Unfortunate situation for many people. We should simplify our life so that we don't need so much power. When I was growing up, we heated with wood. No AC for the few hot summer days and nights. Clothes were hung outside to dry. Our only electricity needs were the lights, refrigerator, washing machine, shallow well water pump and a small water heater. Now, we have two air-sourced heat pumps, a heat pump water heater, dishwasher, clothes washer and dryer, microwave, toaster, air fryer, refrigerator, deep well water pump, hot tub, lights, computers, a freezer in the basement, as well as many "vampire" loads like standby TVs, audio gear, etc. In these times of poor grid reliability due to aging infrastructure and lack of any oversight, increasing rates, as well as the possibility of cyber attacks on the grid, we've chosen to add an off-grid capability to run essential loads like the water pump, refrigerator/freezer and a few lights. Our electric bill is $13 per month, so on-grid has served us well, as long as the grid is up!
 
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macheung

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May 31, 2021
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101
So John, About the original design, do you think the switch is necessary? Why not just use a splitter and wire the off grid inverter and solar edge optimizer together and only turn on the off grid inverter when the grid is out when the optimizer will be in shut down mode?
 

mrzed001

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Apr 10, 2020
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Location
Hungary - EU
I'm annoyed that I can't use my 1-year old SolarEdge inverter without a grid connection, but need to live with it! I've purchased a GroWatt inverter to use when the grid goes down. If you have some time, please comment on the system that I plan on adding to my current on-grid system. I'm using a DPDT switch to switch between the SolarEdge inverter and the Growatt inverter. Any suggestions or ideas are great appreciated! If this works, I'll post the final design. Thank-you. See attached diagrams.

Check out this layout. It has a lot of benefits.

575369_grid_tie_ups.jpg


Your house is always on UPS
Grid-tie produced power powers the house (if enough).
If not enough then the Off-grid produced solar power adds to that
Grid-tie produced power can be stored in the battery (simple utility charging in the off-grid inverter)
Does not need external switch.
 

stienman

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Jan 6, 2021
Messages
200
I can see that your design should work, however it seems overly complicated.

Your solaredge system will work with your own microgrid, so you shouldn't have to switch the solar panels.

Turn off your main breaker and feed the output of the growatt into the breaker box (using a generator breaker interlock).

You can go a step further and use an automatic transfer switch, but unless there are critical loads you cannot allow to lose power, or it happens frequently, then I don't think the cost is justified.

Keep you existing system exactly as it is, and add the following:
- Gro-watt inverter
- Batteries
- Breaker interlock
- 2 additional breakers

Use one breaker with the interlock to connect the output of the growatt to the electrical panel.
Use the other breaker without an interlock to connect the input of the growatt to the electrical panel.
Connect the batteries to the growatt.

You could add an additional interlock to prevent the growatt from having both input and output breakers on, but I'm not sure it's necessary. Here's a kit that does this, though, if needed: https://www.interlockkit.com/product_p/k-9010.htm

This way you don't have to alter the solaredge system at all. When you have an outage, go to the breaker box, turn off the main breaker and the growatt input breaker, and all the loads you don't need powered during the outage.

Then turn on the growatt output breaker, and turn on the growatt inverter. It'll power the house, and the solaredge will come back up and add the solar power to the house as well.

The only thing you need to do at that point is make sure the household is drawing more power from your micro-grid than the solar edge is producing. This can be automated with a zero export rule, set up so the solaredge doesn't push energy into the growatt.
 

mrzed001

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The only thing you need to do at that point is make sure the household is drawing more power from your micro-grid than the solar edge is producing. This can be automated with a zero export rule, set up so the solaredge doesn't push energy into the growatt.

Actually it can work (theoretically). Like it :)
If you put the clamp on the Growatt (or any other Off-grid) AC out cable then the Grid-tie will limit itself. And do not blow up the Off-grid as happened with many users.
The only solution before was (on the same spot) a clamp meter to RasPi. And if backflow close a relay and give some extra load like heater or water heater to use the excess Grid-tie production.

On the breaker side you only need a changeover (1-0-2) switch.
- Set to 1: In a normal case Grid-Tie connected to main (and that is connected to Off-grid AC in)
- Set to 2: In a blackout case Grid-tie connected to Off-grid AC out (with the limiter)
Even can be automated.
 

John Schmidt

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Dec 30, 2020
Messages
36
So John, About the original design, do you think the switch is necessary? Why not just use a splitter and wire the off grid inverter and solar edge optimizer together and only turn on the off grid inverter when the grid is out when the optimizer will be in shut down mode?
I hadn't thought much about splitters until you mentioned it. After looking into it, my main concern would be how the inputs of the optimizers would respond to being connected to two legs of one solar panel, but also one leg of another solar panel (because I need to have the four panels connected in series in order to be above the 120vDC minimum required by the GroWatt MPPT charge controller. I could connect/disconnect the cables as needed out at the solar panel array (280 feet from the house), but would mess something up if I did that more than once! The switch takes the guesswork out of hooking up cables, and shortens the time (if I happen to be standing in snow)!
 

John Schmidt

New Member
Joined
Dec 30, 2020
Messages
36
I can see that your design should work, however it seems overly complicated.

Your solaredge system will work with your own microgrid, so you shouldn't have to switch the solar panels.

Turn off your main breaker and feed the output of the growatt into the breaker box (using a generator breaker interlock).

You can go a step further and use an automatic transfer switch, but unless there are critical loads you cannot allow to lose power, or it happens frequently, then I don't think the cost is justified.

Keep you existing system exactly as it is, and add the following:
- Gro-watt inverter
- Batteries
- Breaker interlock
- 2 additional breakers

Use one breaker with the interlock to connect the output of the growatt to the electrical panel.
Use the other breaker without an interlock to connect the input of the growatt to the electrical panel.
Connect the batteries to the growatt.

You could add an additional interlock to prevent the growatt from having both input and output breakers on, but I'm not sure it's necessary. Here's a kit that does this, though, if needed: https://www.interlockkit.com/product_p/k-9010.htm

This way you don't have to alter the solaredge system at all. When you have an outage, go to the breaker box, turn off the main breaker and the growatt input breaker, and all the loads you don't need powered during the outage.

Then turn on the growatt output breaker, and turn on the growatt inverter. It'll power the house, and the solaredge will come back up and add the solar power to the house as well.

The only thing you need to do at that point is make sure the household is drawing more power from your micro-grid than the solar edge is producing. This can be automated with a zero export rule, set up so the solaredge doesn't push energy into the growatt.
Stienman, I thought that the Solaredge inverter needs to see utility power at all times? If grid power is not available, the SE inverter tells the optimizers to let the input from the panels go to VOC I think, (meaning no current from the panels). If I put it in zero export mode, will it operate without grid power? SE10000H-US Thank-you.
 

stienman

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Messages
200
Stienman, I thought that the Solaredge inverter needs to see utility power at all times? If grid power is not available, the SE inverter tells the optimizers to let the input from the panels go to VOC I think, (meaning no current from the panels).

Correct.

If I put it in zero export mode, will it operate without grid power? SE10000H-US Thank-you.

No. The growatt makes the grid power.

Disconnect from the electric company's grid, turn the growatt on, and the solaredge sees a grid it can contribute to.
 

John Schmidt

New Member
Joined
Dec 30, 2020
Messages
36
Check out this layout. It has a lot of benefits.

575369_grid_tie_ups.jpg


Your house is always on UPS
Grid-tie produced power powers the house (if enough).
If not enough then the Off-grid produced solar power adds to that
Grid-tie produced power can be stored in the battery (simple utility charging in the off-grid inverter)
Does not need external switch.
That would work, if I set up a critical loads panel. I probably should set it up that way, and program the spf-5000-es for grid priority, and install a critical loads panel. I was hoping to get away from a critical loads panel, and just flip on/off the "critical" breakers (as I do now when I need to use the gasoline generator).
 

mrzed001

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Apr 10, 2020
Messages
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Location
Hungary - EU
Stienman, I thought that the Solaredge inverter needs to see utility power at all times? If grid power is not available, the SE inverter tells the optimizers to let the input from the panels go to VOC I think, (meaning no current from the panels). If I put it in zero export mode, will it operate without grid power? SE10000H-US Thank-you.

If main SE unit shuts down optimizers set to give out only 1V.
That is the main reason I like it. If a fire or anything happens there will be no high Vdc arc.
 

mrzed001

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That would work, if I set up a critical loads panel. I probably should set it up that way, and program the spf-5000-es for grid priority, and install a critical loads panel. I was hoping to get away from a critical loads panel, and just flip on/off the "critical" breakers (as I do now when I need to use the gasoline generator).

In this solution you do not need to flip anything. The critical load always gets power (UPS) behind the Growatt.
 

John Schmidt

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Dec 30, 2020
Messages
36
Correct.



No. The growatt makes the grid power.

Disconnect from the electric company's grid, turn the growatt on, and the solaredge sees a grid it can contribute to.
That makes sense. Many people have discussed using an SExxxH-US off-grid, but almost all say that it cannot be done. However, you are first (to my knowledge) that mentioned setting the SExxxxH-US to zero export! So, if that would work, my GroWatt and autotransformer just need to be a glorified split phase 240vAC source. I don't need to reconfigure any panels.

In a power outage (SE10000H-US would already be offline), I would take these steps:
1. Flip off the main 200A breaker on my main panel.
2. Flip off the SE10000H-US 60A breaker in the main panel (probably don't even need this step).
3. Configure the SE10000H-US for zero export using SetApp.
4. Turn on the GroWatt to generate a 240vAC source. The autotransformer creates the neutral for split phase. (need to wire another 2 phase breaker for the GroWatt)
5. Flip on the GroWatt's breaker in the main panel. It is now feeding the main panel with split phase power for the SE10000H-US to see.
6. Flip on the SE10000H-US breaker in the main panel. After a delay, the SE10000H-US should start generating power.
7. Check for smoke!!

Look correct?
 

mrzed001

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Messages
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Location
Hungary - EU
That makes sense. Many people have discussed using an SExxxH-US off-grid, but almost all say that it cannot be done. However, you are first (to my knowledge) that mentioned setting the SExxxxH-US to zero export! So, if that would work, my GroWatt and autotransformer just need to be a glorified split phase 240vAC source. I don't need to reconfigure any panels.

In a power outage (SE10000H-US would already be offline), I would take these steps:
1. Flip off the main 200A breaker on my main panel.
2. Flip off the SE10000H-US 60A breaker in the main panel (probably don't even need this step).
3. Configure the SE10000H-US for zero export using SetApp.
4. Turn on the GroWatt to generate a 240vAC source. The autotransformer creates the neutral for split phase. (need to wire another 2 phase breaker for the GroWatt)
5. Flip on the GroWatt's breaker in the main panel. It is now feeding the main panel with split phase power for the SE10000H-US to see.
6. Flip on the SE10000H-US breaker in the main panel. After a delay, the SE10000H-US should start generating power.
7. Check for smoke!!

Look correct?

In this case can happen that
- Growatt is only working in a blackout and only if manually started ... ugly
- someone accidentally turns on the main (or forgets to turn off) ... BAD.
- main is on and power comes back ... WORST.

None of that can happen with a changeover switch connected to the SE AC out:
- Set to 1: connects SE AC to the main
- Set to 2: connects SE AC to the Growatt's AC output.

SE Limiter (clamp) into the Growatt's AC output cable (normally nothing can flow back, in switch set to 2 SE limits itself).
And you do not need to configure SE in a blackout (zero export set), everything is where it should be and configured.
You only need to change the changeover switch to 2.
Easy
 

macheung

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May 31, 2021
Messages
101
I was experimenting with a similar setup and found a potential solution, still use a relay, but not on the roof. I don't want a relay on the roof as it is a harsh environment and hard to replace if relay fail.

I was able to verify that the SolarEdge optimizer and my MPPT charger operates normally when the solar edge optimizer is inactive (outputting a 1V signal). I am planning to avoid the situation where both an active SolarEdge optimizer and MPPT is on by using a relay at the input of the MPPT charger. This way, I can prevent having a relay on the roof where it is hard to deal with.

I have panels connected both to the solar edge optimizer and the off-grid inverter/charger through a simple Y connector. Before the input of the off-grid inverter, I have a suitable relay for the voltage/amp that is configured such that when the grid is ON, it disconnects the PV from the off-grid inverter. Normally, the off-grid inverter is not connected to the string. During outage, I would manually connect the off-grid inverter. When the grid comes back on, the relay would activate and disconnect the PV from the off-grid inverter before the SolarEdge optimizers turn back on.
 

schmism

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For anyone else that comes along and doesn't want to risk blowing up both systems.

per this video
you can use an "off the shelf" sol-ark inverter to control the solaredge inverter. The sol-ark handling all the switching etc with the grid. Much more expensive than a Growatt however the risk involved for roll your own solution and blowing up both IMHO outweighs the befits of the reduced cost makeing the Solark option a much preferred option.
 
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