My Waterfurnace geothermal heatpump has been working fine for many years (500 foot vertical loop). I recently installed and had it connected to an emergency generator (Cummins natural gas unit that has load shedding capability). When the generator runs with the Geo system running, the generator load display shows less than half generator capacity. When the Geo system stops (thermostat satisfied), a power surge/spike shows on the display that appears to exceed the generator load capacity leading to it shed the Geo power supply. A time delay occurs before the can start up again. The generator installers thought the power surge was related to head pressure when the Geo system stopped. Does this sound like the cause and is there a suggestion to resolve the surge/spike?