Is the thermal load capturing excess heat from the generators?

Excess heat from a generator serves the thermal load if you specify a non-zero heat recovery ratio on the Fuel tab of the Generator Inputs window.  The Help system contains more information on that parameter – you can find it if you look up ‘heat recovery ratio’ in the index.

The schematic diagram tells you whether the system is using recovered heat from generators to serve the load.  This is what it looks like when you are recovering heat:

This is what it looks like when you are not recovering heat: