Question About Preventing Grid Backfeed

[dinosaursolar]

In SBU mode it will use solar and battery together. And switch to grid as a backup if needed.
In SUB mode it will use solar and grid together. And switch to battery as a backup.
Grid and battery together is never a possibility. (always either/or )

I am looking to get the Luxpower SNA 6000 WPV (https://luxpowertek.com/wp-content/uploads/2023/11/SNA-3-6k-user-manual.pdf).

System mainly function as battery back to take advantage of cheaper tariff, time of use. Charge the batteries from 12am to 8am and use battery power from 8am to 12am.

The Luxpower SNA has an option to feedback to grid but can be turned off via settings, however from the thread, it might still export a little, not ideal.

Setup:
Grid > to AC in (SNA 6000)
15kwh battery > (SNA 6000)
(SNA 6000) > Sub panel (all loads)

No PV panel installed.

Settings
PV&AC take load joinly (Disable)
Export to grid (Disable)
"
2. Working as a traditional off grid inverter. In this situation, inverter either use (solar+battery) to takeload or use AC take load. Related settings
" (From the manual)

AC First Start time 00:00 AC First End time 08:00


Does it mean the it will run (SUB - Solar Utility battery) from 12am to 8am and (SBU - Solar Battery Utility) from 8am to 12am?
And seeing that there is no PV installed time frame where SUB and SBU is used. is there a chance for backfeed into the grid to happen?

Thank you

 

[ChrisG]

I am looking to get the Luxpower SNA 6000 WPV (https://luxpowertek.com/wp-content/uploads/2023/11/SNA-3-6k-user-manual.pdf).

System mainly function as battery back to take advantage of cheaper tariff, time of use. Charge the batteries from 12am to 8am and use battery power from 8am to 12am.

The Luxpower SNA has an option to feedback to grid but can be turned off via settings, however from the thread, it might still export a little, not ideal.

Setup:
Grid > to AC in (SNA 6000)
15kwh battery > (SNA 6000)
(SNA 6000) > Sub panel (all loads)

No PV panel installed.

Settings
PV&AC take load joinly (Disable)
Export to grid (Disable)
"
2. Working as a traditional off grid inverter. In this situation, inverter either use (solar+battery) to takeload or use AC take load. Related settings
" (From the manual)

AC First Start time 00:00 AC First End time 08:00


Does it mean the it will run (SUB - Solar Utility battery) from 12am to 8am and (SBU - Solar Battery Utility) from 8am to 12am?
And seeing that there is no PV installed time frame where SUB and SBU is used. is there a chance for backfeed into the grid to happen?

Thank you

Looking at the manual from the inverter you linked, seems like there is a possibility for PV/Battery/Grid to run in parallel and possibly feedback grid.

 

[dinosaursolar]

An off grid AIO won't/ can't backfeed the grid.
With one exception, SUB mode.
SUB mode allows the AIO to operate in parallel with the grid. And act like a hybrid AIO in zero export mode. It has the same advantages and disadvantages for that setup.
This type of function wasn't a problem until the utility meters became super sensitive to micro bursts of export.

I am thinking since i have no PV my system will funtion in two states.

State 1 (12am to 8am)
Power from grid in bypass mode, to charge batteries and power load.

State 2 (8am to 12am)
Power loan from batteries.

Will the inverter run in parallel with the grid? and hence have a slight chance of back feed?

 

[timselectric]

I am looking to get the Luxpower SNA 6000 WPV (https://luxpowertek.com/wp-content/uploads/2023/11/SNA-3-6k-user-manual.pdf).

System mainly function as battery back to take advantage of cheaper tariff, time of use. Charge the batteries from 12am to 8am and use battery power from 8am to 12am.

The Luxpower SNA has an option to feedback to grid but can be turned off via settings, however from the thread, it might still export a little, not ideal.

Setup:
Grid > to AC in (SNA 6000)
15kwh battery > (SNA 6000)
(SNA 6000) > Sub panel (all loads)

No PV panel installed.

Settings
PV&AC take load joinly (Disable)
Export to grid (Disable)
"
2. Working as a traditional off grid inverter. In this situation, inverter either use (solar+battery) to takeload or use AC take load. Related settings
" (From the manual)

AC First Start time 00:00 AC First End time 08:00


Does it mean the it will run (SUB - Solar Utility battery) from 12am to 8am and (SBU - Solar Battery Utility) from 8am to 12am?
And seeing that there is no PV installed time frame where SUB and SBU is used. is there a chance for backfeed into the grid to happen?

Thank you

I'm not familiar with that unit. But since it runs in parallel with the grid , it can export. (Even when told not to)

 

[timselectric]

I am thinking since i have no PV my system will funtion in two states.

State 1 (12am to 8am)
Power from grid in bypass mode, to charge batteries and power load.

State 2 (8am to 12am)
Power loan from batteries.

Will the inverter run in parallel with the grid? and hence have a slight chance of back feed?

It is a possibility.

 

[bhbaker220]

May be a technicality, but it would appear to me that an off grid inverter can export electricity if the grid is down ... if it is wired through a sub panel that is connected to the main panel (or to the main panel directly) and the breaker is on and there is no interlock kit. This is what scares the crap out of the utilities and if I were a lineman, it would scare me as well.

 

[ChrisG]

May be a technicality, but it would appear to me that an off grid inverter can export electricity if the grid is down ... if it is wired through a sub panel that is connected to the main panel (or to the main panel directly) and the breaker is on and there is no interlock kit. This is what scares the crap out of the utilities and if I were a lineman, it would scare me as well.

That’s a different problem than the inverter allowing grid feedback after large loads stop and inverter doesn’t throttle down quick enough.

 

[timselectric]

May be a technicality, but it would appear to me that an off grid inverter can export electricity if the grid is down ... if it is wired through a sub panel that is connected to the main panel (or to the main panel directly) and the breaker is on and there is no interlock kit. This is what scares the crap out of the utilities and if I were a lineman, it would scare me as well.

Yes, if connected incorrectly it will be a problem.

 

[dinosaursolar]

Good to know thank you.

Is there anyway i can test this inverter to see if it back feed the grid?

Or to test if it runs in parallel with the grid?

How would i go about doing it?

 

[timselectric]

Good to know thank you.

Is there anyway i can test this inverter to see if it back feed the grid?

Or to test if it runs in parallel with the grid?

How would i go about doing it?

If it's in any mode, where it's using grid and either solar or battery together, it is running in parallel.

 

[bhbaker220]

You could buy a monitoring system like Emporia Vue with a couple of CT's around leg 1 and leg 2 wires coming into your main panel to see if you are exporting. My smart meter is able to read not only the kwh incoming into the house, but also reads and documents the amount of kwh exported. I'm on Entergy in Texas and don't know if most of the smart meters that have been installed have this capability.

 

[ChrisG]

You could buy a monitoring system like Emporia Vue with a couple of CT's around leg 1 and leg 2 wires coming into your main panel to see if you are exporting. My smart meter is able to read not only the kwh incoming into the house, but also reads and documents the amount of kwh exported. I'm on Entergy in Texas and don't know if most of the smart meters that have been installed have this capability.

@bhbaker220 how does backfeed show up in the emporia. I accidentally backfed before and didn’t see it in the monitor.

 

[bhbaker220]

@bhbaker220 how does backfeed show up in the emporia. I accidentally backfed before and didn’t see it in the monitor.

I have a grid tied inverter and see it all the time with a negative reading on one or both of the mains. It matches up fairly well with the utility company but the lowest frequency they report from their system is in 15 minute intervals. I have an off grid inverter on a manual transfer switch and have never tried to intentionally backfeed.

 

[bhbaker220]

I have a grid tied inverter and see it all the time with a negative reading on one or both of the mains. It matches up fairly well with the utility company but the lowest frequency they report from their system is in 15 minute intervals. I have an off grid inverter on a manual transfer switch and have never tried to intentionally backfeed.

In the EMporia Vue setup, you do need to tell it that you have solar installed. I don't recall all of the additional steps that I needed to go through but you can call them for help. I have CT's on the mains as well as on the breaker for the grid tied inverter.