LVX6048 with Solaredge autotransformer

[Carlsbad_Solar]

I have a LVX6048 120V/240V from MPP Solar which is grid tied including a small solar array and a 280Ah LiFePO4 battery. I use the battery between 4-9PM when energy rates are their highest using a timed relay to disconnect from the grid. I have really run into a situation from day one when a few simultaneous kitchen appliances will overload one leg of the inverter while on battery. I have done my best to balance the circuits including moving appliances around, but I haven't had much luck. Obviously, I should have gone with a larger inverter, but I am stuck with this for now.

My question is whether I can use a solaredge autotransformer to help balance the load at the panel?

1.) I am not sure if the auto transformer can be connected while on grid power?
2.) Would I need to remove the neutral going from the inverter to the panel?

I was really hoping to just find a way to help balance the load on the inverter.

Thanks for the advice.

 

[timselectric]

My question is whether I can use a solaredge autotransformer to help balance the load at the panel?

Yes

I am not sure if the auto transformer can be connected while on grid power?

It should not be.

Would I need to remove the neutral going from the inverter to the panel?

Yes
The autotransformer will be creating the neutral.

Those are the short answers.
But it's more complicated than that. When you have the grid connected to the input of the AIO. And try to use an autotransformer, instead of an isolation transformer.

 

[Hedges]

I think you can get some benefit connecting autotransformer to inverters, keeping neutral to inverter. I would rather it was disconnected when there is pass-through from grid.

I have tried autotransformer rebalancing split-phase inverters.
It was connected through long wires (extra resistance) and provided only modest percentage rebalancing. Neutral was not disconnected so transformer was not creating neutral, just sharing some of the imbalanced current.
I plan to install it later, with much shorter wires. It will be switched, only connected when off-grid. It will also serve to create second (split) phase if all but master inverter sleep.

 

[Carlsbad_Solar]

Thank you both for providing some guidance. If I have understood your advice correctly.

1.) Auto transformer should be disabled while on the grid.
2.) The neutral on the inverter may or may not be used while off grid and using the auto transformer. I think there is a difference of opinion on this.

 

[Hedges]

People have connected auto-transformers while on-grid, but depending on grid imbalance and wire resistance, your tiny autotransformer may try hard to rebalance it. Extra current flow, may get hot. No benefit, so we recommend disconnecting. Those who did do it had 240V only inverters, were trying to create neutral.

If neutral of inverter is not used,
1) load will be perfectly split across the inverters.
2) Imbalance between two 120V loads is limited to what auto-transformer can deliver
3) If auto-transformer is disconnected (e.g. if protected by breaker), neutral is lost and the 120V loads on each phase will determine what imbalanced voltages they receive.

There are some autotransformers e.g. from Victron that address transformer protection and 240V pass-through better.

If neutral of inverter is used,
1) auto-transformer will only partially rebalance the load, so you won't be able to reach 100% of both inverter capacity.

 

[timselectric]

That ?

 

[Sun in Lithium]

The lvx6048 is has a center tap transformer built in that has a constant draw of around 120w ?

I don't know if a second transformer will play nicely with it.

 

[Hedges]

Current magnitude times volts magnitude = VA

But if that current is close to 90 degrees out of phase (because an inductive load), then it returns power during the next phase.

Current vector times volts vector = W

I've used my digital scope to capture the two and calculate real & apparent power.

Your clamp ammeter reads DC as well. Check DC current from battery and see if the watts you think are being burned are actually coming from battery, or if that is closer to documented idle power.

 

[Sun in Lithium]

Good point. reactive power used by the transformer can't be calculated by simply timesing the max current by max volts.

I have tested the dc side of the lvx6048 and in stand-by and it came to 140w constant draw.