Solar with existing back up Generator

[jayrob]

We installed solar on a home that had a back up generator. The electrician that installed the generator is saying that we did our interconnection incorrectly. I'm hoping to get some information to confirm.

It is a 400A MSP split buss.

His generator breaker is on the side that has all the house loads.

Our solar is on the other side of the split buss with no loads. (supply side connection)

Any thoughts as to why he is saying we are interfering with his generator? Aren't we completely isolated on the other side of the split buss?

Thanks in advance!

 

[jaggedben]

There's not enough info to say. Is there a transfer switch, and if so where is it located? If not, how is the switch to generator power normally handled?

A split bus by itself does nothing to isolate the generator from the solar if they are both on the same side of a transfer switch. It would be fine if there's a transfer switch that isolates the generator's side of the split bus from where you connected.

 

[jayrob]

Hmmm let me get more information thanks...

 

[GoldDigger]

Just for completeness, the reason that a standard grid interactive inverter must not remain active and connected to the generator output when the grid is down is twofold:
Most obvious and least important from a safety perspective is that the generator output may not be stable enough and accurate enough for the GTI to accept it as a valid grid, so the GTI may shut down on transfer and not restart
Less obvious but more important is that the typical GTI does not have any mechanism to throttle its AC output below the available PV energy.
As long as the wattage of the loads connected after transfer is greater than the maximum PV output this will not be a problem. But if the PV output ever exceeds the local load the GTI will attempt to backfeed the generator. And unlike the POCO grid the generator cannot accept reverse power and will either shut down, go out of regulation stopping the GTI, or in the worst case be damaged.