boiler vs tankless hot water heater for in floor heat ( space 88 by 60 split into two separate area and supplementing heat source with an in-farred system in each area). Will the hot water heater Enternal Hybrid 98% water heater Model GU-145 of GU-195S work for what I need?.
Only if it's approved and accommodated for by the manufacturer. The main problem is that they can commonly be sending out water that's too hot, because they can't be set low enough. Which in turn, means a much larger on/off range has to be instituted and you end up with uneven heating with a quite uncomfortable cold period.