A Fan Coil Unit (FCU) capacity is directly affected with Entering Water Temperature (EWT). FCUs are rated for EWT= 60C but with a heat pump delivering EWT=35C, capacity drops by 31%. 

 This is derived from detailed data from a manufacturer like Media. 

If we assume that EWT= 60 C is reference point, then heating capacity change with different EWT differentials can be calculated from figure below: