Safe Grid Use of the 5000ES and transformer

[timselectric]

Btw, if the inverter firmware was updated to allow disabling AC bypass while allowing the 80amp charger to be used...I think that would resolve this whole problem. Maybe something to raise with the supplier...

I don't think that this would be just a firmware issue.
If I'm not mistaken, the connection to the AC charger is after the bypass relay.

 

[Hedges]

This feature would be great on Off-Grid installations, Back-up generator would only have to be big enough to charge batteries (80A). Instead of powering all loads and charging batteries.

I think that is ideal. For occasional ‘big’ loads like a tablesaw you can work that out.

The feature you want is an inverter that can synchronize to AC input and feed inverter output in parallel with grid. That could support net-metering (UL-1741), or be zero-backfeed measured at grid input to inverter, or with external CT be zero export to grid measured at utility meter.

Such inverters can be programmed to limit grid current to whatever level you want, be it 10A or 50A. This is normally done with a bidirectional inverter/charger, but could be implemented with separate battery charger circuit. It requires the inverter to synchronize with grid/generator input before connecting, and then at least measure grid current & phase for zero backfeed. I'd rather it implemented UL-1741 as well to safely shut off if grid goes down. "zero export" may have power exporting on one phase and importing on the other, due to imbalance of load.)

To utilize inverters without such feature, an external battery charger seems simplest. That won't let you driver bigger loads than inverter can handle, need those fed directly from generator. But it makes inverter and battery management simple.

 

[timselectric]

The feature you want is an inverter that can synchronize to AC input and feed inverter output in parallel with grid.

The SPF-5000-ES has this feature. ("SUB" solar/utility/ battery)
Solar and utility share the loads, with solar being priority.
Battery is kept full, and on standby.
Battery only feeds the loads, when solar and utility are unable to.
When battery is connected to the loads, utility is disconnected.

 

[ajccmc]

I don't think that this would be just a firmware issue.
If I'm not mistaken, the connection to the AC charger is after the bypass relay.

Arg, too bad. I have located a 2P NC and 2P NO , 63amp contactors So the NO will go in the AC IN side, the NC will go on the AC out side. In normal operation neither coils will be energized. If I need to charge the batteries, that implies I have grid available to energize the coils, charging the batteries while keeping the autotransformer disconnected. Just need to come up with how to decide to enter charging mode. Still exploring if I can tap into the RS485 connections or sourcing a voltage monitor.

 

[timselectric]

Arg, too bad. I have located a 2P NC and 2P NO , 63amp contactors So the NO will go in the AC IN side, the NC will go on the AC out side. In normal operation neither coils will be energized. If I need to charge the batteries, that implies I have grid available to energize the coils, charging the batteries while keeping the autotransformer disconnected. Just need to come up with how to decide to enter charging mode. Still exploring if I can tap into the RS485 connections or sourcing a voltage monitor.

Just to make this clear in my head.
When charging the batteries, you won't have power to the loads?

 

[LeRoyK]

Arg, too bad. I have located a 2P NC and 2P NO , 63amp contactors So the NO will go in the AC IN side, the NC will go on the AC out side. In normal operation neither coils will be energized. If I need to charge the batteries, that implies I have grid available to energize the coils, charging the batteries while keeping the autotransformer disconnected. Just need to come up with how to decide to enter charging mode. Still exploring if I can tap into the RS485 connections or sourcing a voltage monitor.

Can you use the dry contact built into the inverter? see attached.

 

[timselectric]

If you use a DPDT relay on the output side.
You could simultaneously connect the loads to the grid.

 

[timselectric]

Can you use the dry contact built into the inverter? see attached.

This setting was removed, several months ago.
You would have to be using a unit from before the removal. And, not updated it.

 

[ajccmc]

Just to make this clear in my head.
When charging the batteries, you won't have power to the loads?

The grid will power the loads via the transfer switches downstream from the autotransformer. When they see power drop from the inverter/autotransformer and power is available from the grid, they switch to the grid, If power come back from the inverter/autotransformer they switch back to it. hope this helps.

 

[ajccmc]

Can you use the dry contact built into the inverter? see attached.

I looked at that, but... if the battery is charged NC & C are closed... and if the inverter is in bypass mode its closed also! Thus I don't think I can for sure isolate bypass mode. Correct me if I'm wrong!

 

[timselectric]

The grid will power the loads via the transfer switches downstream from the autotransformer. When they see power drop from the inverter/autotransformer and power is available from the grid, they switch to the grid, If power come back from the inverter/autotransformer they switch back to it. hope this helps.

I see
Thanks

 

[Trip.Diamond]

No
The only way that they provide grid power, is through the bypass relay. And ac charging can also only be done, when bypass relay is on.

This may not be entirely correct. I have one taken apart and have been trying to trace out the power flows through the unit.

I have not fully tested this so I could be wrong but…
What it seems to do, in what I call “Grid Assist” mode (SUB setting), is pass the Grid power through the charge controller and back into the Inverter section of the unit. This creates an AC-DC-AC coupling that would prevent any back feeding of the Grid. (and avoid any need to frequency match the Grid.) This is also one of the reasons why it requires a battery if more then one SPF5000 is used in parallel.

This would limit the output when in SUB mode to the 5000watt limit of the Inverter.

Again I have not yet had time to test this yet.

 

[timselectric]

This may not be entirely correct. I have one taken apart and have been trying to trace out the power flows through the unit.

I have not fully tested this so I could be wrong but…
What it seems to do, in what I call “Grid Assist” mode (SUB setting), is pass the Grid power through the charge controller and back into the Inverter section of the unit. This creates an AC-DC-AC coupling that would prevent any back feeding of the Grid. (and avoid any need to frequency match the Grid.) This is also one of the reasons why it requires a battery if more then one SPF5000 is used in parallel.

This would limit the output when in SUB mode to the 5000watt limit of the Inverter.

Again I have not yet had time to test this yet.

This may be true. And entirely feasible. It would be the safest way to do it. My main point was that battery and utility are never connected to the loads, at the same time.

 

[timselectric]

If the sun ever decides to shine on my panels again. lol
I'm going to test the limits of SUB.
Which could confirm that.

 

[ajccmc]

If the sun ever decides to shine on my panels again. lol
I'm going to test the limits of SUB.
Which could confirm that.

Would this confirmation indicate that I don't need to put contactors on the AC in/out as we have discussed?

 

[timselectric]

Would this confirmation indicate that I don't need to put contactors on the AC in/out as we have discussed?

No
It doesn't change anything.
If you want to use an auto transformer, and be connected to the grid.

 

[timselectric]

If Solar and grid can both power the inverters load panel at the same time, then my question is if the inverter will still shutdown once inverters output of 5000w is exceeded.

Still can't get the sun to shine for me.
This is typical, when you want to test something. lol
But, I just decided to push on, and pay for the electricity to test with.
I ran out of things to plug in, easily.
But, I pulled 6.5kw , and it didn't shut down.
I did get a warning light, so I left it running for 10 minutes. Never even acted like it was a problem, other than the warning light.

 

[timselectric]

This may not be entirely correct. I have one taken apart and have been trying to trace out the power flows through the unit.

I have not fully tested this so I could be wrong but…
What it seems to do, in what I call “Grid Assist” mode (SUB setting), is pass the Grid power through the charge controller and back into the Inverter section of the unit. This creates an AC-DC-AC coupling that would prevent any back feeding of the Grid. (and avoid any need to frequency match the Grid.) This is also one of the reasons why it requires a battery if more then one SPF5000 is used in parallel.

This would limit the output when in SUB mode to the 5000watt limit of the Inverter.

Again I have not yet had time to test this yet.

Done some testing.
It appears that in SUB, it does send AC power into the inverter circuitry, to synchronize with it. But, the bypass relay is always engaged. Also verified this with a meter. So, I assume that it monitors the current, similar to grid tied inverters and maintains zero export.

 

[Trip.Diamond]

Done some testing.
It appears that in SUB, it does send AC power into the inverter circuitry, to synchronize with it. But, the bypass relay is always engaged. Also verified this with a meter. So, I assume that it monitors the current, similar to grid tied inverters and maintains zero export.

WOW! That is bit unexpected. Despite all of the negative “press” these inverters are receiving these days I continue to be impressed with their capabilities. If only the US version had a simple signal to shut off the Autotransformers when in BYPASS mode it would be great inexpensive and safe choice!

It does bring up some question though as to how it avoids back-feeding the Grid.

Unfortunately the way I have mine setup right now I can’t use SUB mode to test anything. (I am using a current sensor on the AC input line to shutoff my Autotransformers so it only works in SBU mode)

Does it turn on AC BYPASS mode right away when you switched it to SUB mode or did it only turn on when you exceeded inverter output? Also I wonder if it only switches on only when you exceed Solar power?

 

[timselectric]

WOW! That is bit unexpected. Despite all of the negative “press” these inverters are receiving these days I continue to be impressed with their capabilities.

Same here

If only the US version had a simple signal to shut off the Autotransformers when in BYPASS mode it would be great inexpensive and safe choice!

Agreed
I was able to set mine up, with a non US version.
Much easier to do, with the ground relay still intact.

Does it turn on AC BYPASS mode right away when you switched it to SUB mode or did it only turn on when you exceeded inverter output?

Emidiatly
Any time grid is connected to the loads.
First , it makes the bypass connection. Then, it connects grid to the inverter. After a few seconds (I assume that this is the time required to synchronize) the inverter connects to the load.
A lot of dotted lines, on the display. lol