Back-feeding a generator with Solar

[JoeNorm]

I have read that it would be unwise to ever let solar panels back-feed a generator.

Why is this? What will be damaged in the generator? Will take a long time to see? Or would it be immediate?

I do not understand the interaction in motors well enough, figure someone here might know.

Thanks

 

[topgone]

Any generator when being "back-fed", "motorizes"! If that ain't bad for you, what is? Even parallel generators are protected to never motor each other, what a waste of energy!

 

[jaggedben]

The basic reason is that a grid-tied solar inverter is typically configured to output the maximum power available from the solar panels, not to follow the load. If there aren't loads to consume that power, then that power will try to go somewhere, and generators aren't design to consume power.

We discussed the issues in more detail in a recent thread here:

Isolating generator from solar system

I have a customer who just had a whole house generator installed at their home where I had put solar panels a couple of years ago. The solar system backfeeds the main panel through a 40-amp breaker. The power to the house comes underground for a pedestal about 150' from the house. The...

forums.mikeholt.com

 

[tortuga]

Bottom line is it can be done and you need some budget to play with, SMA makes a inverter called a 'sunny island' that can accomplish this, with a very minimal battery setup. https://www.sma-america.com/products/battery-inverters/sunny-island-4548-us-6048-us.html