How do I wire a GTI system with an AC GENERATOR, anyone here got a simple diagram... what do I need?

Do you expect the GTI solar (Grid Tied Inverter) to work with the genset when the utility power has failed (or want to do an off grid genset+GTI)?

In general, it will not work. The GTI does not support (add its power) to the genset for several reasons.

1. GTI is not regulated. The GT Inverter simply takes all of the energy from the solar array and pumps its into the local AC wiring. If the GTI output exceeds the local AC loads--There is no place for the energy to go other than "backwards" through the geset alternator. At that point the local AC voltage will exceed the GT inverter's maximum and will cause the inverter to shut down (5 minute timeout typical, then retry).
2. For smaller AC Gensets with mechanical speed/RPM regulation, the output frequency is not stable/accurate enough for GT inverter (+/- 0.1 to 1.0 Hz or so). Again, if the frequency is "wrong", the GT Inverter will shut down for 5 minutes and retry.

If you are looking at large AC gensets--You might find a system that does work with GTI solar. That is outside the experiences of most of our people here.

The typical way home/small business systems do Grid Tied and Off Grid solar is to use a "Hybrid" inverter (does both off grid and grid tied) with a battery bank. This is for systems that are in the range of 4 kWatt to 8-30 kWatt (typical--You can connect many hybrid inverters together for a much larger system too).

The system looks like: Solar panels -> solar charge controller -> battery bank -> Hybrid Inverter -> local AC backup power panel

And the AC side: AC mains -> Hybrid Inverter AC1 input -> local AC backup power panel
And AC genset: AC genset -> Hybrid Inverter AC2 input -> local AC backup power panel

The the utility mains are up; The solar power both charges the battery bank and any excess power is sent to the AC mains (for use by local loads and "backwards" to the AC mains).

When the AC mains are down; The solar power charges the battery bank and solar+battery supplies the AC local backup power (Hybrid inverter has its own AC transfer switch to disconnect from the AC mains).

If the battery bank needs charging: The Hybrid inverter will start the genset and enter "Generator Support Mode". The genset will supply AC power and the hybrid inverter will take any excess genset power and recharge the battery bank. If the AC load exceeds the genset AC output rating, the hybrid inverter can take battery+solar power and "help" (or "support) the genset output AC output (i.e., the system will support a maximum power of AC Genset+Hybrid Inverter power ratings).

The downside--You need a large DC battery bank. You have the costs and maintenance of a battery bank. And batteries need to be replaced every 5-10 years or so.

-Bill