The Interconnection Limit is an upper limit on grid purchases and sales (kW) for every time-step. HOMER will attempt to meet any remaining unserved load with onsite generation sources such as battery, generator, wind etc. If the load is still unmet, the simulation is declared infeasible. The option to add an interconnection limit to HOMER Grid is located on the Project > Settings pages. To apply an interconnection limit to your model, check the box and enter a non-zero positive value for the maximum kW allowed.
Grid Sale limit is an upper limit on sales to the grid at any timestep. This limit can be specified for each tariff.
If the interconnection limit is less than the Grid sale limit, the Interconnection Limit will override the Grid Sale Limit. This would mean that your grid sales cannot exceed your interconnection limit. If your Grid Sale Limit is higher than your interconnection limit, you will see a warning.