If your saying my grid is high your wrong
Wrong user's picture, . . .sorry, grasping straws.
Something may be wrong with the EG4. . . "Over-voltage" would need to be pretty darn high, perhaps the unit has a faulty sensor somewhere. Did you put a meter on the EPS outputs, and verify the voltage? Better yet put a recording meter on the HVAC AC line. Are you connected with anything to the "GRID"? If so what is the voltage on your grid lugs? I know the EG4 will easily handle 50A, thus I suspect something odd at play. None the less, if you are connected at the grid lugs with house power I would turn off that breaker and test.
Then again, it's possible your "Easy Start" has failed, coincidentally with your inverter swap. I would roll up my sleeves and start getting some voltage and current readings. A cheap recording multimeter/ammeter can be had on Amazon, you don't really need precision, just an idea of where you are. I would re-seat/re-torque all my electrical connections from the inverter to the panels/switching/whatever. You made a pretty big change swapping out two for one, with new wiring, something may have "jiggled" loose, or gotten twisted.
It never hurts to pull the cover on the HVAC and verify the wiring there, toss us some pics of the physical interconnects from the inverter to the panel. I can't tell you how many times I've solved an issue by simply walking it back. Oh, grab a temperature gun while you are at it shoot the various connection points. Unlikely you are going to blow up your HVAC, unless you have some ridiculous numbers. Pictures of the connections walk it from the HVAC, pull the cover, visual/physical inspection, re-seat the outside disconnect, check the fuses, make sure everything is tight. Pull the panel cover, verify the connection at the breaker is tight, check the connections at the panel to the inverter feed, and then back at the inverter.
The ususal, turn off the HVAC unit at the thermostat, verify voltage the entire way down at each point all the way to the contactor (S/B 0). Cut the power again, put the meter / probe on the wire just in front of the easy start, turn everything back on, start the HVAC, while monitoring the connection at the HVAC. If you see a problem post it here. I'm not buying a surge issue if you are only pulling 49-50A on start.