Eg4 18kPV grid input but no backfeed

[Jdcarrol]

Hello. We’re near the end of our diy set up but have an ask. In our home we have 2 circuit breaker boxes, main and sub-main.

Sub-main is powered by a breaker from main.

Our 18kPV is powering sub-main only. As a backup on a cloudy day or extreme heat I’d like to have the main panel have a line ran into our inverter grid input but with the guarantee that it will NEVER backfeed into the grid for safety and our desire to be off grid. The grid input is to reassure the wife that if our PV+power all is not enough that her and kiddos can be comfy

Does the software setting have an option to take in grid power when needed but NEVER backfeed?

 

[zanydroid]

This may help.

What is the difference between Off-Grid Mode and Run Without Grid in the android app for the EG4 18Kpv?

These sound the same to me. I've had both active at the same time, and did not notice any problems. I am now running with the Run Without Grid and the Power Backup settings ON with Off Grid setting OFF.

diysolarforum.com

Why get a 18kpv when grid tie interconnection (and possibly also skipping permits) were not needed? There are much cheaper alternatives

 

[BentleyJ]

The description of your set up doesn't make any sense. How is the subpanel powered from both a breaker in the Main panel AND the 18kpv? Is there manual transfer switch? If so Why.

Typically the inverter AC input is fed by a breaker in the main panel and then the inverter AC output feeds the subpanel. This configuration gives you the most options with regard to time of use offsetting, battery back up in case of an outage, aux battery charging from utility during multiple cloudy days.

If you wanted to use the inverter as a secondary source of power for the main panel, but only when there is a grid outage, then the Inverter Output could feed another breaker in the main panel. This breaker would have to be interlocked with the main breaker using an interlock kit so that only one breaker (source of power) could be feeding into the main at a time.

 

[zanydroid]

I agree copious photos are mandatory here given the effectiveness of the OP prose.

We will look at them.

I interpreted OP assuming it was set up in one of the ways that make sense in reality, and it was only the prose that was illogical.

 

[Jdcarrol]

Thank you everyone for the responses, I think I have been able to get the information I need from the various insights; however, let me respond to the further questions/comments to make sure I do understand. I think I did a poor job explaining.

Point 1: I do agree that there may be cheaper ways to do things. Although I’d consider myself a good gardener, I am no electrician and the solution we are going with is what gave my wife enough confidence in letting us go down this journey

Point 2: Here is more insight into

This may help.

What is the difference between Off-Grid Mode and Run Without Grid in the android app for the EG4 18Kpv?

These sound the same to me. I've had both active at the same time, and did not notice any problems. I am now running with the Run Without Grid and the Power Backup settings ON with Off Grid setting OFF.

diysolarforum.com

Why get a 18kpv when grid tie interconnection (and possibly also skipping permits) were not needed? There are much cheaper alternatives

I was/am just ignorant wanting to over engineer to reduce the chance of getting something wrong.

 

[Jdcarrol]

This may help.

What is the difference between Off-Grid Mode and Run Without Grid in the android app for the EG4 18Kpv?

These sound the same to me. I've had both active at the same time, and did not notice any problems. I am now running with the Run Without Grid and the Power Backup settings ON with Off Grid setting OFF.

diysolarforum.com

Why get a 18kpv when grid tie interconnection (and possibly also skipping permits) were not needed? There are much cheaper alternatives

This does help, thanks!

 

[Jdcarrol]

The description of your set up doesn't make any sense. How is the subpanel powered from both a breaker in the Main panel AND the 18kpv? Is there manual transfer switch? If so Why.

Typically the inverter AC input is fed by a breaker in the main panel and then the inverter AC output feeds the subpanel. This configuration gives you the most options with regard to time of use offsetting, battery back up in case of an outage, aux battery charging from utility during multiple cloudy days.

If you wanted to use the inverter as a secondary source of power for the main panel, but only when there is a grid outage, then the Inverter Output could feed another breaker in the main panel. This breaker would have to be interlocked with the main breaker using an interlock kit so that only one breaker (source of power) could be feeding into the main at a time.

We not looking into a manual transfer switch, here is a bit more explanation of our set up, sorry if I was initially confusion.

The set up we’re going for with our 18kPV

We’re using the 3 PV inputs. The Load will be tied to a sub panel. This sub panel was previously powered by our main panel, but this connection will be permanently disconnected. We’re looking to now bring an AC line from our main panel into the grid input of our inverter. I’m not concerned about the load output going into the main breaker box and/or grid as it’s physically separate. I guess my question is, Is there a possibility that the inverter can backfeed via the grid input? And if there is a possibility, is there a setting to not allow that? Seems like there is by using off-grid mode?

 

[zanydroid]

The Load will be tied to a sub panel. This sub panel was previously powered by our main panel, but this connection will be permanently disconnected. We’re looking to now bring an AC line from our main panel into the grid input of our inverter

This sounds really "overly dramatic." As I understand it, you have an existing feeder into the subpanel. You can "undo" the permanent disconnecting by reconnecting the feeder into the subpanel. Seems pretty darn reversible (hence why I think it's expressed dramatically for engineering/technician purposes. For project mission statement purposes maybe it's OK).

In fact, majority of people plan for bypassing an inverter that is defective or under maintenance, which means disconnecting AC input to the inverter and connecting it directly to the AC output. Either by redoing connections or by having a two-throw transfer switch.

I guess my question is, Is there a possibility that the inverter can backfeed via the grid input? And if there is a possibility, is there a setting to not allow that? Seems like there is by using off-grid mode?

The link I provided implies that the 18KPV can be placed in a strict off-grid mode. Off-grid AIOs are supposed to be able to work in SBU mode (Solar, Battery, Utility - in that order). With utility air-gapped from the inverter output.

18KPV is a premium product so you should be protected against the problem of AIOs improperly wired/programmed to provide this guarantee. You should call EG4 or your vendor to confirm. Or tag the official EG4 support people on this forum. Since without an interconnection agreement you need to be air-gapped properly.

Are your batteries one of the EG4 ones approved for UL9540? I don't know if your state or AHJ cares about that, you do have solar panels up, a rather visible modification to your property, so that may invite permitting scrutiny.

 

[EG4_Jared]

Hello. We’re near the end of our diy set up but have an ask. In our home we have 2 circuit breaker boxes, main and sub-main.

Sub-main is powered by a breaker from main.

Our 18kPV is powering sub-main only. As a backup on a cloudy day or extreme heat I’d like to have the main panel have a line ran into our inverter grid input but with the guarantee that it will NEVER backfeed into the grid for safety and our desire to be off grid. The grid input is to reassure the wife that if our PV+power all is not enough that her and kiddos can be comfy

Does the software setting have an option to take in grid power when needed but NEVER backfeed?

The 18kPV does have a Fast Zero Export and Off-Grid mode so that you would not backfeed to the grid if desired.

 

[Jdcarrol]

This sounds really "overly dramatic." As I understand it, you have an existing feeder into the subpanel. You can "undo" the permanent disconnecting by reconnecting the feeder into the subpanel. Seems pretty darn reversible (hence why I think it's expressed dramatically for engineering/technician purposes. For project mission statement purposes maybe it's OK).

In fact, majority of people plan for bypassing an inverter that is defective or under maintenance, which means disconnecting AC input to the inverter and connecting it directly to the AC output. Either by redoing connections or by having a two-throw transfer switch.


The link I provided implies that the 18KPV can be placed in a strict off-grid mode. Off-grid AIOs are supposed to be able to work in SBU mode (Solar, Battery, Utility - in that order). With utility air-gapped from the inverter output.

18KPV is a premium product so you should be protected against the problem of AIOs improperly wired/programmed to provide this guarantee. You should call EG4 or your vendor to confirm. Or tag the official EG4 support people on this forum. Since without an interconnection agreement you need to be air-gapped properly.

Are your batteries one of the EG4 ones approved for UL9540? I don't know if your state or AHJ cares about that, you do have solar panels up, a rather visible modification to your property, so that may invite permitting scrutiny.

We're using the EG4 powerwall, we waiting for the version that has the proper certification. I see an EG4 person on this thread now, yay!

 

[Jdcarrol]

The 18kPV does have a Fast Zero Export and Off-Grid mode so that you would not backfeed to the grid if desired.

View attachment 205559

Thank you so much!

 

[Delicious]

The 18kPV does have a Fast Zero Export and Off-Grid mode so that you would not backfeed to the grid if desired.

View attachment 205559

Would you mind clarifying explicitly if the Off-Grid mode should be enabled if I want to use the grid as a 3rd source of power, but cannot export any energy due to the lack of an interconnection agreement?

When I enable this option, I see a small amount of energy (300-400W) pushed to the grid, which may be because my batteries are >90%. It seems a little counterintuitive that I should enable the "Off-Grid Mode" option when I do actually want to use the grid as a 3rd power source. It's also confusing to me that any energy would be pushed to the grid when "Grid Sell Back" is disabled.

Thanks!