I am trying to find coefficients in biquadratic curve for gas condensing boiler, from the manufacturer catalog. I have only the following data: rated output at 80/60oC 91.9kW rated output at 50/30oC 98.8kW boiler output modulation at 80/60oC 18.2kW (! This is I believe PLR minimum value of app 0.2 when Tret=60oC or Tsupp=80oC) boiler output modulation at 50/30oC 19.6kW (! The same as above only at different conditions) standard efficiency at 40/30oC (LHV/HHV) 110%/99% standard efficiency at 75/60oC 107%/96% efficiency at rated load at 80/60oC 97%/88% efficiency at 30%PLR and Tret=30oC 107%/96% This boiler operates with maximum supply temperature of 65oC. I am not familiar with regression analysis but from what I read in engineering reference I do not have enough data to generate my own coefficients. Can I use coefficients from boiler data set since in data set stands: "! Gas-fired condensing boiler ! Normalized boiler efficiency coefficiencts derived from two boilers; ! One with 40C supply, 30C return and one with 75C supply, 60C return ! Use curve below for a condensing boiler having a nominal thermal efficiency of 0.89." and nominal thermal efficiency of my boiler is 0.88? Also, if I were to contact the manufacturer should I ask for efficiency at various PLR and supply temperatures? Thanks in advance Marko