The collector model as described in 25.1.4.2, should cover most collector designs available on the market, except ICS collectors. If the full collector model should be applied for a certain type of collector (or collector design) or not, will in general be given by the result of the parameter identification, but for all types of collectors, the use of η0,b, Kθ(θL, θL), Kd, and the coefficients c1, c2, and c5 are mandatory and they should be identified. In the exceptional case that coefficient c2 comes out negative or has no statistical significance (i.e. if T-ratio (parameter value/standard deviation of parameter value) is smaller than 3,
the parameter identification should be repeated without c2 included in the model.