The Heart Interface inverter/chargers qualify the input power before engaging the internal transfer switch and turning on the charger
. The methods of qualification vary somewhat according to the model and software
If the frequency of the genset is off between 1 and 3 Hz (again, depending on above) or if the input voltage is too low or too high the unit will not come "on line". I've also discovered that if there is a problem in the neutral bonding as in an intermittent or poor quality it can affect the unit from qualifying the input power. The neutral of the generator
is supposed to be well bonded to the green wire ground and genset chassis as a source whenever the genset is running or switched in the system as a source.
If you have any of the Link monitors installed in conjuction with the inverter/charger it is easy to see when the unit has qualified the input power by looking at the green LED for AC IN on the remote
Some gensets, particularly the lower power ones like 5kW or less, have pretty non-uniform waveforms which get further distorted when the charger
attempts to put out full power and sometimes the distortion causes a "de-qualification" and the unit drops off line. At those times it is sometimes to remedy the problem by running a heater or other resistance-only load (assuming that your genset has enough power do do both) so that the charger remains on line.
Other more detailed symptoms?