Heterogeneous nucleation of supersaturated n-butanol vapor on neutral silver particles of different size has been investigated at variable nucleation temperatures using a fast expansion chamber and a commercial continuous flow type condensation particle counter (CPC). In addition, the theoretical supersaturation profile was calculated for the commercial CPC in order to conflate the results with the measured onset saturation ratio of the expansion type size analyzing nuclei counter (SANC). A comparison of the experimental results of the SANC measurements with the Kelvin equation shows that the heterogeneous nucleation starts below the Kelvin curve. By introducing a correction factor for the Kelvin equation based on the SANC measurements, the theoretical detection efficiency for a laminar flow type CPC could be derived. It was the first time that a validation between theoretical saturation ratio profiles and measurements conducted with different methods to generate supersaturation was achieved. We made the observation that reducing the nucleation temperature generally leads to enhanced counting efficiencies. Consequently, the cutoff diameter of regular butanol CPCs can be significantly reduced by simply lowering the condenser temperature.